• 2 Stroke Forum
• 2 Stroke Motorcycles

Rules within the EU mean you can no longer buy a new, small 2-stroke outboard motor in Europe, but their light weight, compact size and longevity means tens of thousands of used examples are still to be found on boats from Caithness to Crete. The start of the season is when any unreliability issues are most likely to rear their ugly head, and there’s a good reason for that.

‘Most people assume they can just take their outboard off their boat and put it straight into their shed for the winter,’ technician Steve Dawkins told me in his workshop at the Cabin Boatyard on the Hamble River. ‘Then, come the spring, they’re surprised when it doesn’t work.’ I kept quiet. My outboard had been sitting forlornly in the garage among a pile of ropes, fenders and sails since it came ashore at the end of last summer. Do it yourself! This step-by-step guide takes you through a service of a small 2-stroke outboard. The pictures show Mariner 3.3hp and Suzuki 2hp outboards, and while other makes of engine are subtly different, the main components should be recognisable. Anyone with a reasonable level of technical ability should be able to breeze through the service, but if you’re in any doubt, take yours along to a dealer.

If you are going to do it yourself – and this mostly applies to late-model motors – check first that what you’re doing won’t invalidate any warranties. 1: Drain the old fuel ‘The most common complaint we get is from people saying it worked fine last year but now it won’t start,’ said Steve. This is because petrol evaporates over time, leaving behind an oily, paraffin-type residue which gums up the carburettor.

So the first step is to drain the old fuel. 8: Now reattach the gearbox to the lower leg.

Carefully slide in the gearbox, making sure the water pickup pipe (small spigot just above the gearbox linkage in this photo) is unblocked and lined up correctly inside its socket. On smaller engines with only one gear Remove the propeller and then the plate behind it. The water pump impeller can be found behind this plate.

Check and replace the gearbox oil The professionals perform a pressure test to check the seals are still doing their job. Without the right equipment you’ll struggle to do this, so you’ll have to make do with a visual inspection. One way to see if you have a major problem is to leave the engine standing on a piece of clean cardboard overnight and check for telltale leaks in the morning.

Introduction: These articles are put together from actual experiences over a 50 years, mainly because my memory is not anywhere as good as my wife's. I am not a marine mechanic, but have been an outboarder and have done my own repairs all my life and a machinist forever. I document here what I have encountered, so that I can go back and read my own writings if something pops up years later. For these outboard motor repair articles, I DO NOT try to give the reader a documented list of parts needed for a conversion, (as this could be different because of running changes made even within the same models), but do try to document what differences I have encountered and tricks I have learned, many of which are not listed in service manuals. I have also tried to break out specific areas of repairs into separate articles, however some may overlap.

For these, you may see a slight duplication, but with a more complete write-up on the article more specific to that repair. My articles are probably the most complete information you will find for the 9.9/15hp Johnson/Evinrude motors, however they can be extensive and dull reading for the person who has no clue as for outboard repairs. I often get inquiries, which I try to answer, however most of the time, the information requested is there, if that person would have taken the time to read farther. This article covers many aspects of these series of OMC motors, but over the years it has grown to the point that I have had to split it into separate specific sections. In doing so, you will see a CLICK HERE or Yellow Highlighted underlined link that takes you to the article that is specific to what is being discussed. Some links to online information will have the link in an underlined blue color. 1993 & Newer Motors: It appears that this same basic 2 cycle motor has not really changed even up to when they were discontinued (2002 but sold until 2007 or until stock was depleted).

If you need to look up replacement parts for a motor sold during or after 2002 you will not find it listed as a 2 cycle, but only 4 stroke motors, so you will have to go back to a 2001 parts list. About this time many of the manufacturers started not using year model numbers as we knew it, but the year it was sold. Some new motors were sold later, usually within a couple of years as new/old stock, still with a 2 year warranty.

I have even heard of a new one that got slid far back in a dealer's floor and sold new in 2009. I have seen some advertised as new, however I suspect they were simply carry overs as described above.

Rumor is that the 2 cycle motors were not made after 2001 due to the fact that they knew these motors could not meet upcoming Federal EPA requirements. Now to avoid some confusion here, the 9.9hp were made in both 2 AND 4 stroke motors overlapping with the 4 stroke coming into being in 1995. These 4 stroke motors had the powerheads made by Suzuki, but used basically the same lower unit as the existing Johnson's. In 1993, the OMC, Johnson/Evinrude 9.9 / 15 hp motors took on basically a complete makeover other from the previous version, (except it used the cable throttle tiller system brought out in 1987 then modified in 1990) including the power head, eliminating some problems while improving the design in some areas.

This came about because of the previous imported outboards were outrunning the domestic motors of the same horsepower as the imports were rated differently. This meant that after 1986 they had to make about 10% more real hp than the 85's due to the inherent hp loss in the lower unit gearbox. Because of this, the motor underwent a new design change increasing horsepower plus a new look as far as the motor cowling and many bolt on units to the block. They used this as a chance to make major improvements. The cowling now separates on basically a horizontal line as compared to the older angled to the rear line. This motor has a taller profile than the earlier pre 93 motors and weighed a bit lighter because of plastic replacing the aluminum lower motor housing. These 9.9 hp motors were cataloged as that until 2003 when the labeling changed to 10 hp, same motor, just a different horsepower label.

The only real difference between this series of 9.9 and 15hp motors is the carburetor and the decal. The 15hp carburetor has a larger throat and main-jet, which then allows more fuel and air to be sucked into the engine, allowing it to turn up a higher RPM, which then gains the higher HP. This increased RPM is usually from 700 to 1000 higher for the 15hp.

The 2000 Johnson manual states the following specs for the 15hp: Full Throttle Operating Range 5000-6000 RPM Power rated at 5500 RPM Idle RPM in gear 700+/-25 Weight Rope start 72#, Rope start Long shaft 77#, Electric start Long shaft 80# Displacement 15.6 cu in Bore 2.375' Stroke 1.760' Gear Ratio 12:29 (0.414) Gear-case capacity 9 fl oz Fuel 50:1 mix Then in 1999, OMC introduced the 4 stroke models which were only marketed under the Evinrude name. They still made the 2 cycle motors (covered here) and marketed them under the Johnson name. The 4 stroke 9.9 / 15hp were made using Suzuki powerheads, with pretty much the rest of the motor being the same as this previous 2 cycle.

The 4 stroke driveshaft used different splines into the crankshaft of the powerhead. I have to admit that I have never seen one of these 4 stoke motors.

Year of Manufacture: This is important in any repair, for obvious reasons. Here is a to help you determine any of the Johnsons. And here is the for the Evinrudes. For those of you readers outside of the United States, here is another that may better help with your motors.

After 1979, OMC's manufacturing year code, which included Evinrude, is the word 'INTRODUCES', with each letter equating to a number ie: I =1, N =2, T =3, R =4, etc. As illustrated below. As before, the last 3 letters are what you are looking for.

Then in this case, disregard the last one, as it pertains only to a model revision that only on specific cases may be reverent to a marine repairman if problems arise. A code of J10ELENA would equate to J ohnson, 10hp, Electric start, Long 20' shaft, EN = 1 992, and the A could be a model revision, so this motor would probably be made in the very first part of the year. You may encounter a code of something similar to J10SELCTC. This would have been Johnson, 10hp, SailMaster, Electric start, Extra Long shaft, 1983, and the C could be a model revision. In this case with the SE in the model number, indicating a SailMaster.

All the SailMasters would have all had the extra long 25' shafts and electric start. At one time Evinrude's equivalent of the Johnson SailMaster would have had the name Yachtwin. These were designed to be used as an auxiliary power for sailboats, hence the extra long shaft. For more detailed information on worldwide production. CODE I N T R O D U C E S CODE 1 2 3 4 5 6 7 8 9 0 Using this code system, if the motor was sold as an Evinrude, then the first letter would have been an E instead of the J.

Then you can encounter motors made in or for other countries, which will have some added letters as mentioned later in this article. There should be the model and serial number on riveted on 1” X 2” aluminum ID plate on the LH side of the transom mount bracket (looking forward). Sometimes this ID plate can get removed. If this happens, you can still usually tell which motor it is by looking at the 25 cent size soft plug in the upper rear RH side of the block. The model and year are stamped in this soft plug also but probably only up to 1979. It is interesting to also note that the 15 hp uses the same block as the 9.9, so you could see a 15 hp with the same 10R78M numbers here as the 9.9 has. I have heard from more than one person that their plug had numbers that do not match any of the codes, so this kind of backs up the idea of a change after the 1979 date, as the factory changed things as time went on. If you need to check on parts and do not have a actual parts list booklet, one of your best sources is They have a complete listing of about all of the Johnson and Evinrude motors showing exploded parts views with part numbers where you may be able order parts online from them.

Or this one Power Head: The piston diameter was increased to 2.365' requiring a different head gasket and displacement was upped to 15.6 ci. or 255.64 cc. The.015' spacers under the reed valve stops designed for the 15 HP being used for both motors. So now the basic motor has been redesigned to increase the HP for the 15hp unit without the add ons required to achieve it's rating, with the 9.9 now being the detuned version. The center main bearing is different, apparently of a larger size. The head is arranged so that the spark plugs are on the Left Hand side of the block. The manual starter has been redesigned, moved which is then supported by 2 over arms above and in front of the flywheel with another over arm attached to the block in the rear.

The manual starter engagement dogs are on the inside of a ring in the flywheel. The flywheel nut has been enlarged which is now 7/8'. I solved this problem by milling.031 off each flat of the nut thereby making it the same 13/16' size as the spark plugs. The flywheel key is also wider than the pre 93 motors. The thermostat housing was left on top of the head, but was changed somewhat and made of plastic that uses a round formed O-ring type seal.

The thermostat is totally different and more easily constructed. Next to and somewhat incorporated into the thermostat housing is a provision for a high temperature kill switch that is only installed in the remote electric models. The fuel pump is the same basic one as used on the late 1987 and later motors up to at least 40 hp. Electric Start Motors: The electric start motor mounting bolts come in from the outside and are bolted directly into the block, instead of the bolts coming in from the top into the sideplate cover.

The starter relay mounts onto the LH side of the block in front of the starter motor. The starter contact switch is buried in the tiller handle's base close to the shifting lever. It however is about impossible to replace unless the powerhead is removed as the channel where the wires are routed are hard to get to and be able to fish the end connectors out even with the carburetor removed. This starting system has been modified from the old pre 93s in that the starter switch is just a contact button, energizing a heavy duty relay to the actual starter. These later actual push buttons are attached to the rear of the shift lever independently of the contact switch & it also acts as a neutral safety switch by being rotated either above or below the contact switch by the shift lever, which will then not engage the contact button unless the shift lever is in neutral. This push button system could be considered hard to get to by some as it is quite out of the way.

It surely will not be engaged accidentally. Shown in the RH photo below, you can see the location where the ground wire is bolted to the front of the block. The hot wire runs farther rearward and connects to the starter solenoid. Starter push button behind & connected to the shift lever with the contact switch directly behind it.

Here is where the ground wire is attached. Basics for Starter Solenoids: Number one in troubleshooting is to be sure the battery is fully charged. This does not mean 12 volts, because at about 11.5 volts a 12 volt battery is almost dead. When charging it is not uncommon to be at 14 volts, with a fully charged battery being about 13.5 volts. If the starter does not spin, the solenoid is bad OR the starter is bad OR the battery is dead. Here we will coach you thru the testing so you can evaluate your own situation.

The solenoid has 2 circuits, one circuit puts voltage from your battery to the starter motor. These are the 2 large gauge wires attached to the solenoid by the 2 large studs/nuts. One large wire comes FROM the battery to the solenoid, the other large wire leaves the solenoid and goes TO the starter.

This we will call the HIGH amperage circuit, because it powers the starter itself. Many times the input wire is red. The other circuit is the control circuit ( these are the 2 small studs/nuts on the solenoid).

This will be the LOW current circuit. This circuit controls the solenoid when you turn the key to the Start position or push the starter button. Low current (control circuit) test: When you turn the key to the start position, voltage is fed INTO one small terminal of the solenoid. This voltage goes thru the solenoid, then continues OUT of the other small terminal to one side of the Neutral Safety Switch. The other side of the Neutral Safety Switch goes to a ground connection (if the motor is in Neutral). This completes the circuit and the solenoid closes. When the solenoid closes, it puts battery voltage thru the large gauge wires to the starter and the motor cranks.

Here is the solenoid for most all OMC motors from 1993 on for the 9.9 up to 200hp OMC Part #: 584580 If the motor is NOT in neutral, the neutral safety switch breaks the control circuit not allowing the solenoid HIGH amperage circuit to make contact. Since the solenoid can't close, it can't send voltage to the starter thru the large gauge wires. This is a safety issue. They don't want you to be able to start the motor 'in gear'. OK, how do you test if the solenoid is OK or not! Here's the quick way.

BE ABSOLUTELY SURE MOTOR IS IN NEUTRAL, and the ignition key is in the OFF position. This testing procedure will bypass the Neutral Safety Switch and test the solenoid. On the solenoid, find the small post with the wire going to the neutral safety switch.

Momentarily connect this small post to any metal part of the motor (ground) with a jumper wire (holding the jumper wire by hand will do). Turn the key to the start position, starter should turn over. If the starter spins, the neutral safety switch is bad, OR the wire going TO the neutral safety switch has an open (broken) OR the neutral safety switch ground connection is bad. High Amperage (direct circuit) test: You have to be careful of gasoline fumes when you 'Jump the solenoid'. There can be sparks when you make this connection. Here is how you can bypass the solenoid altogether to see if it is OK.

Use a heavy wire, (10 gauge or so) to light a gauge of wire to 'jump' the 2 large terminals of the solenoid will put voltage to the starter, but the wire will not be large enough to transmit enough amperage and will get hot fast because the starter was drawing a lot of current. A light gauge wire could not carry enough current and it will heat up if held there for time enough to start the motor, and burn you if not careful. That's why they use heavy wires! If during this jump test, the starter momentarily engages, you can assume the starter is OK. Starters can draw large amounts of current. It's not uncommon for a starter to draw 50 Amperes of current when you turn the key or press the start button. Marine solenoids are designed to contain any internal sparking for this reason.

That's why it's safer to test the 'control circuit' (small posts) side of the solenoid. Most of the time, starter problems can be traced to bad connections. Especially the High Amperage circuit. Corroded connections are points of high resistance that limit the amount of current passing thru that connection that decreases the amperage needed by the starter to spin. These connections to look at will be the Positive and Negative battery posts, the two large terminals of the solenoid, the starter connection, and the starter ground connection. To clean these connections, remove the Positive battery connection first, and then leave it disconnected while you clean the other connections.

This eliminates the possibility of accidently shorting any wires to ground during the cleaning process. Clean the other connections (one at a time) and make sure they are clean and bright and securely tightened. Finally, re-connect the Positive battery connector when you are finished. Don't forget the Negative connection to the motor block too. A motor could have one or more of these problems, but highly unlikely. Tiller Handle: The tiller handle has been moved to more of a central location instead of off to the left as previous motors.

The shift lever is now on the tiller handle at the front of the motor above the mounting clamp screws. There is an adjustment at the base of the shift lever/electric starter button whereby a neutral safety position can be achieved.

This is accomplished by the shift lever being positioned so that the starter push button does not engage the starter electric button behind it in the tiller arm if the shift lever is not in neutral. Clamping Bracket and Tiller Handle: The clamping bracket for the standard tiller motors the pivot shaft has not been changed, but there is no good simple factory provision that I have found for a tie together rod for steering from the main motor. Look at the photo below for my solution to this situation. I made a sturdy aluminum angle then found a spot on the base of the tiller handle to attach it.

DO NOT DRILL & TAP directly to this tiller handle, you need the angle material at least 1/4' thick that comes up behind the outer edge. It (the aluminum) can be drilled and tapped for 1/4-20. The reason is that this tiller handle is not made of aluminum as most would think, but is a high strength nylon which may well need the backing inside support of this aluminum angle plate. Custom made tiller tie in bracket attached to tiller handle For the remote control motors it is now made so that a push/pull steering cable goes thru the hole in the tilt pivot shaft like the later larger motors that are set up for remote steering. New Carrying Handle: Another carrying handle has been added to go crosswise of the motor on the forward side of the clamps, making it easier to position the motor on the transom & is attached to the main motor tilt shaft and when not in use lays back out of the way. The old carrying handle below the clamp screws still remains.

The steering handle is moved more to the center of the motor instead of on the far LH side. This steering handle/twist throttle utilizes pretty much the same Man Over Board kill button as the 89-92 motors did. 1993, notice the different cowling cover shape's more straight line & the lower cowling extends lower 2001 15 hp, electric start Flush Adapter: There is a flushing plug on the top RH side of the power head's water jacket sideplate so you do not have to run the motor in a tank to flush saltwater from the internal water jackets.

This plug uses a standard 3/8' course thread which can utilize the Mercury type flush adapter that is so commonly used by the outboard jet motors. This apparently is NOT designed to run the motor as if you were using muffs, as the water flow would be entering the water pump from the wrong side. This just appears to be a flush location for use with the motor NOT running. Lower Unit: The lower unit has changed slightly with removable external plastic water intake screens. The housing as a cast in receptacle for inserted zinc anodes on the sides. These anodes are both the same part but one is just flopped 180 degrees to be used on the other side instead of the afterthought ones of the previous years. There is one stainless steel 10-24 bolt and nut that goes thru them for attachment.

This lower unit is basically the same for the 2 stroke with most internal parts the same as the 74 - 93 models. The 4 stroke motors that came out in 1995 were a Suzuki powerhead while using a lower unit that looks quite similar, but has a different number of attaching bolts, so it will not fit the OMCs. The gears, shaft and seals appear the same as the earlier versions as well as the water pump assembly. The upper motor mount has been greatly improved internally as shown below on left. However the photo on the right was sent in by a reader ' I have a 1993 Evinrude and made the mistake of driving a very rough road towing my boat with the motor attached. The consequences are that the two bolts that attach the pivot tube to the exhaust housing sheared off.' This repair would involve the powerhead have to be removed as the 2 broken bolt heads are under the caps of the LH photo.

Shown here is the arm that is the extended end of the twist grip throttle which rotates the timing plate. The manual starter unit also being totally different than the pre 93s. Note the built in provision for the electric starter & location of the spark plugs on the opposite side of the head This series too, will be undergoing more improvements of it's own. Carburetor: The carburetor shown below looks externally very much like the pre 93's but internally the pickup tube and main-jet are simplified. Notice the side located idle jet adjustment screw.

This screw threads into to plastic top of the carburetor which has finer threads than the previous models. The 'Go To' thread back out to begin your idle setting will be about 4 1/2 threads out from bottomed out. I have found that on my motor about 4 5/8 turns out seems to be about right.

The reason for this number of threads turned out instead of the 1 1/2 for the pre 93 motors is that these later plastic topped carburetors have a finer threaded idle needle. Like 0.45 MM per thread (or near 50 TPI) where the pre metal topped carburetors have 28 TPI. When you remove the plastic top you may notice on the bottom of the plastic at the location of this side idle adjustment screw, where the brass threaded sleeve the screw threads into may have swelled the bottom of this top cover downward slightly.

If this is bad you may want to slightly file off some of the plastic in that spot to again give a better contact with the rubber gasket. As with the previous year carburetors using plastic tops, if you encounter hard to start or idle problems, c heck the new plastic cover for any hairline cracks, especially near the low speed needle location. If air passes through into the needle valve, it won't start worth a damn, and likely not idle well. You can successfully seal this crack with JB Weld. Plastic carburetor covers are inexpensive, less than $20.

On the plastic top and bottom you will find numbers near the screws. These are for sequence of tightening the screws.

In the plastic bottom is a drain screw in the RH side. The one problem encountered here is that there is little room for a wrench on the LH carburetor attachment nut. It is suggested that for this LH nut that you use a 7/16' combo wrench and grind out the front closed section. You may also have to grind the handle slimmer, or make a slight recess close to the head to allow clearance. Even so you will only be able to get one flat at a time.

Also tighten this nut completely FIRST so you can test whether the carburetor is tight before you use the wrench to tighten the RH nut. This will assure you that both nuts are tight otherwise if the LH one is loose, you will get a air leak at the carburetor/manifold leak that may be hard to detect if the motor is not running right.

One suggestion when re-installing the carburetor, lay a shop rag under it above the lower pan. There is a Black Hole under it where the shift linkage enters that will gobble up the carburetor mounting nuts that drop off before they get started onto the threads. This is directly under the carburetor area and goes down into the pivot housing area. This rag will create a catch area for lost nuts. The timing plate cam that activates the carburetor throttle arm roller has been improved with a helical cam matching the roller's advance. There is a timing mark on this cam plate that coincides with the touch point with a simple adjustment screw. There is a slow and high speed throttle linkage stop at the rear of the RH block where the throttle linkage pivots, whereby 2 adjustment screws control the movement of the linkage.

The manual choke would be the significantly recognizable difference between the pre 93 motors as shown on the carburetor shown below. It is however is hard to remove the choke lever from the carburetor while the lower cowling is still in place unless you remove the roll pin that activates this lever which is inserted into a hole on the choke butterfly shaft. A simpler replacement for the roll pin is a piece of 1/16' bronze welding rod that the bottom end that goes into the shaft, be slightly upset to hold it in the shaft. This is easier to remove and replace than the original steel roll pin.

Also in these newer plastic fuel bowls you can see a drain plug threaded into one side of this plastic bowl. There may also be another boss on the opposite side. This could because these parts seem to be as universal as possible, fitting many different carburetors. Some of these motors do not use a choke, but a fuel primer, if this is the case, this second boss can be tapped and act as a fuel supply for the primer instead of teeing off of the carburetor's fuel inlet line.

These primers inject raw fuel into the rear of the carburetor and behind the high speed butterfly. In the upper RH rear you will see the new idle adjustment screw, ELIMINATING THE IDLE KNOB OFF THE FRONT as found on the earlier models. But making it necessary to remove the upper cowling to make the idle adjustment. It also eliminates the possibility of enriching the carburetor for a cold start situation.

The carburetor breather box has been changed so that the intake is buried underneath and now making it about impossible to squirt fuel into the carburetor to start a stubborn motor, unless you pull the breather box off. This Carburetor is off a 1993 9.9 Johnson & is the same all the way up to the end of production in 2001 RH VIEW LH VIEW In 2002, the motors were all 4 stroke and the carburetors were changed completely, eliminating the plastic tops. Carburetor Timing: If you are having problems getting the motor to run as you think it should, possibly where the timing plate is considerably advanced, you may consider doing a 'Link and Sync' of the carburetor throttle arm roller to the timing plate cam. The throttle cam plate that rotates under the flywheel when you twist the twist grip and the plate has an raised line type mark on the front of it. This mark needs to be timed so that when you advance the throttle twist grip, that the carburetor roller is at this mark when the carburetor throttle shaft just STARTS to turn open Fuel Pumps: These fuel pumps are normally a pretty trouble free mechanical device mounted on the LH side of the block below the flywheel.

They are a diaphragm type pump which is activated by vacuum created below the pistons of the motor thru a hole into the inside the motor’s side plate that leads into the crankcase. There is a filter screen on the outside of the fuel pump retained by one center screw that you may want to look at occasionally. The primer bulb is a fuel pump of sorts. It's purpose is to initially pressurize the fuel system and once the motor starts, the motor takes over using internal engine pressure and alternating vacuum inside the block to activate the fuel pump, sucking fuel from the tank. With the motor running your bulb is no more than a fat piece of fuel hose so you can expect it to be soft at that point.

2 Stroke Forum

The repair kit is #433519 for these fuel pumps. Later large fuel pumps mounted directly to the LH side of the block Coils & Power Pack: The coils now are a dual coil unit as compared to the individual coils used prior to 93. It is interesting in that these coil packs are used on many different motors. 9.9 -15hp 1993-up, 40hp 1989-up, 50hp 1989-up, 90 -115hp 60º blocks 1995-up (2 required), 150 -175hp 60º blocks 1991-up (2 required).

The power packs, like about all of the current aftermarket ones have a built in rev limiter, usually set at 6200 RPM. What this does is not allowing the motor to 'run away with itself' by electronically not allowing the motor to over rev. The wires are all plug in ends for the coils, input wires and spark plugs. For the electric start motors, the rectifier uses bullet type connectors instead of screw eyes attached to a terminal strip as for the pre 93 versions.

But the older rectifiers are the same electronically, so you can if needed, simply replace the eyed ends with the bullet type. Throttle Cable: Occasionally you may encounter one of these throttle cable systems that the twist grip will not stay where you put it. The motor will usually slowly slow the speed down by itself if you let go of the twist grip throttle. A solution shown in the earlier section for this was passed on by a retired marine mechanic. His solution was to take a electricians #4 or #6 copper grounding split bolt clamp and simply clamp it around the throttle cable in an out of the way place. There is enough room on these models to place it on the cable beside the carburetor.

2 Stroke Motorcycles

Tighten the nut enough to just squeeze the cable inside the plastic sheath. This allows for the cable/twist grip throttle to function normally but with just enough friction to keep it from creeping slower. Works like a charm.

#4 copper grounding clamp squeezing the throttle cable on a 1994 motor There is lots of nylon/plastic being used in construction of these motors, but the flywheel is all cast iron not aluminum as on the previous series of these motors. Lower Motor Cowling: The lower motor cowling is made in 2 pieces of a plastic type material that allow you to get to the lower sides of the motor by simply removing 5 or 6 screws. This allows work on the powerhead that was not possible on the pre 93 motors. There is rubber foam insulation on each inside of these lower cowlings to help cut down noise, but also absorb water or leaking fuel. T hese plastic cowlings however are subject to breakage way more than the older aluminum versions. Even by using the new plastic repair epoxy, repairs are not very strong, at least the ones I have attempted. J-B Weld seems to do a better job, but it needs a metal backing support.

And the price of new cowlings are in the $100 range for each side range. I have been searching shops or eBay for some time and ones for sale are very limited, so my guess is the demand is great for them.

As you can see below I have fashioned a internal 1/8' aluminum patch then bolted it to the cowling. I started with the patch on the outside, but it was quite unsightly. This inside one required making a cardboard pattern, much cutting and bending, more bending, installing, removal and more bending. Bolt heads showing on the outside is something I can live with compared to shelling out $100. I had to cut a plastic reinforcement web out at the rear of the cowling where the rubber bumpers go. These bumpers are for support when storing the motor laying it on it's back.

The bumper will now be bolted in place instead of it being held there by tits of rubber snapping inside a hole. The problem is that the fit has to be pretty darned close in order for the top cowling to fit properly, lock down and yet not place a lot of strain on the new $18 plastic latch used on the 93-96 models that I had just installed. These lower cowlings were the same for the 93 thru 96 motors with the latch being a plastic push lever type that would have a lot of strain on it if the tilt unit became somewhat seized and hard to lift the motor to a lock tilt for traveling as a auxiliary motor. In 1997 they went back to a lever latch type.

The 97 and later lower cowlings will bolt onto the 93-96 motors, but the matching top cowling will also have to be used because of the newer latch system. The 97 and newer latch was a revert back to an improved version of the earlier pre 93 rotating lever latch.

You will also note that there is rubber foam glued to the lower insides for noise insulation. The fuel pump cover/screen intake line is connected to the fuel connector on the cowling itself. The simple way to remove these cowlings is to unscrew the fuel pump cover, as this is the only motor attachment after the cowling's (4 or 5) 10-24 bolts are removed. The nuts for these bolts are 10-24 square to allow them to be inserted into a pocket and not rotate. Left side lower cowling repair for a 1994 One problem that has been encountered, is since the lower cowling is now plastic with the upper cowling being secured to it by a latch on the rear, that IF the tilting pivots are not greased regularly, maintaining a easy lift when pulling the motor up out of the water when used as a auxiliary motor, that there is a lot of strain on this early type 93-96 rear plastic cowling latch.

This can therefore lead to latch breakage. In the photos below, the left one shows the latch system from the inside. The wide center tongue (which has no latch knob, but is just a guide) goes into a mating slot of the lower cowling's latch unit. The horizontal coil spring is what actually snaps under a section of the lower plastic latch. This lower latch is all plastic so when you pull the outer rear latch which has the arrow on it, this lower latch releases the coil spring. 1997 cowling rear latch system 1997 cowling rear latch peg shown from the inside The bolts that attach the powerhead to the mid-section are 1/4' stainless using a Torx T-30 wrench. The overboard water indicator tube comes off the top of the sideplate with this rubber tube just sticks out of the RH lower cowling.

It protrudes out the same hole that you use a screwdriver to tighten the inner lower rear cowling screw. This makes it easy to inspect or clean it out if suspected debris may be plugging it. Start In Gear Override for Manual Starter: One thing that many fishermen prefer, is that the motor can be restarted in gear. This would be if they were trolling, stopped the motor to land a fish then wanted to restart at the preset trolling speed if not using the throttle adjustment knob in the tiller handle. On about all of the Johnson/Evinrude motors, the motor has to be in neutral to start, apparently for safety's sake. I have found a simple method to override this function, and yet not delete it, as shown in the photo below.

This will only work for a manual starter motor as the electric start has a different neutral safety switch described in in a earlier section above. Shown in the RH photo below is a Red-Neck version that also works. The neutral start override conversion shown by the arrow. Red-Neck Zip-Tie overide This simple override is just a piece of 3/32' aluminum, with a hole drilled in it. Installation is by a 6-32 round head machine screw that is threaded into the LH edge of the nylon plunger lock. When fitted the aluminum is slightly smaller that the plunger lock body and is offset to the left so that in use it is pivoted upwards in a vertical position with the top edge being just high enough to prohibit the lock from being pulled inward buy it's spring system. If you want to return it to normal usage, just rotate the aluminum 90 degrees to the right, since this piece is just smaller and in alignment with the plunger lock, it then functions normally.

This just locks out the plunger lock from going inward and stopping the manual starter spool while in forward gear. Converting a 9.9 to 15 HP: This question seems to pop up quite frequently and can get controversial from those who have never been associated with the conversion while are only going from what they have heard. As you can see from the above information in this article, it is possible. New carburetors are expensive, (well over $200), but used ones go for about three quarters of that, then you can probably expect to rebuild it. Some will tell you that you need different reed valves and reed valve stops, not so.

The situation here is that THIS motor was designed as a 15 hp and detuned for the 9.9 hp version. The only difference between the 9.9 and 15 hp motors of this 1993 version is the carburetor (which has a larger throat) and the decal on the side of the cowling. Now in 1994 they changed the reed leaf for the 9.9 only. This was probably to improve the idle characteristics. So from 1994 to the end of production in 2001, the 9.9 hp used a different reed leaf valve than the 15hp did.

Remember that these 2 cycle motors were sold up to 6 years or so later after production ceased. On these later motors (1993 +) the exhaust tube is the same for both sizes.

I have not truly tested a before /after on the same boat, same water conditions. Also if your boat is to large, heavy or you and your fishing buddy plus gear are overloading the boat, your conversion benefits will not show. However if you have a lighter boat and it just needs a nudge to get it onto a plane, then possibly going to the 15hp would help. The larger carburetor will gain the most in increased RPM, (about 1000 RPM more, according to OMC) which in this case also relates to more horsepower. If you insist on squeezing that last ounce of energy, then maybe the aftermarket reed valves, polishing and deburring the intake manifold will be of some benefit. But, if you are trying to push it this far, at wide open throttle for an extended period of time, yes you may get away with it, but if some small thing goes wrong, it could get compounded quickly and damage the whole motor. If this happens you need to be sure you have a couple of paddles onboard.

If you try to get one on eBay, be very careful that it is indeed a 15hp (larger throat) and the right choke version (manual or remote electric). Some of those wontabee outboard parts sellers have no clue what fits what. And the 15hp carbs are priced at a premium because of the exact reason you may be wanting to change over. You will not find new 15 hp carburetors even listed as a separate salable part anymore. Look at changing props as well if you are trying to push a heavy boat.

Props are listed the same for both the 9.9 and 15 hp motors and are interchangeably used from 1974-2005, however depending on the weight of your boat, it may be advantageous to try a lesser pitch version. Observations: This motor appears to be an improvement in some ways over the 'small block' pre 93 motors. However here are some of my observations. I like the shifting lever on the tiller handle.

I am not overly fond of the electric start button's hidden hard to get at location. This button is hard to get to if you are in a hurry, emergency type situation and if the shifting lever is not precisely in neutral the starter button will not engage. The plastic lower cowlings easy removal makes for easy access to the lower part of the block if need be, I see a benefit to using a separate starter button/solenoid on these motors. The manual starter is a better design which makes for a bit more leverage for cranking manually, however it adds to the overall height of the motor that those of us who are more used to the pre 93 motors have become accustomed to. For some reason even with foam insulation on the insides of the cowlings these motors are noisier than the earlier models.

As for idling, I used my 94 for one salmon season trolling and it did not idle at a troll as smooth as my 92 version. Maybe it was simply because these newer carburetors do not have an external readily available idle jet as the earlier motors did where I simply did not take the time to remove the upper cowling each time I thought I might want to fine tune the carburetor.

Exploded P arts Lists: If you need to check on parts but do not have a actual parts list booklet, one of your best sources is They have a complete listing of about all of the Johnson & Evinrude motors showing exploded parts views wit h part numbers and you can order parts online from them. Copyright © 2005 - 2015 LeeRoy Wisner All Rights Reserved Originated 08-31-05, Last updated.