OMC, Johnson, Evinrude outboard motors 1993 thru 2005

1993 & Newer Motors:  It appears that this same basic 2 stroke motor has not really changed even today (2006).   Rumor is that the 2 stroke motors will not be made in 2007 due to the Federal EPA requirements.

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 & modified in 1990) including the  power head, eliminating some problems & improving the design in some areas.  The motor underwent a new design change & a new look as far as the motor cowling & many bolt on units to the block.  The cowling now separates on basically a horizontal line as compared to the older angled to the rear line. 

The piston diameter was increased to 2.365" requiring a different head gasket & displacement was upped to 15.6 ci.   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.  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 & now is supported by 2 over arms above & 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 & is now 7/8", so if you may have to remove the flywheel in the field, your old spark plug wrench will not work on this model.   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 & made of plastic & uses a round formed O-ring type seal.   The thermostat is totally different & more easily constructed.   Next to & 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 & later motors up to at least 40 hp.

The electric start motor mounting bolts come in from the outside & 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 & 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.  The actual push button is 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.  

Starter push button behind & connected to the shift lever with the contact switch directly behind it.

The shift lever is now in the center front of the motor above the mounting clamp screws.

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 & 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 & 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 & may well need the backing 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. 

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 & 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 OverBoard kill button as the 89-92 motors did.

1993, notice the different cowling cover shape's more straight line & the lower cowling extends lower

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 & 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.

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 & 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 & nut that goes thru them for attachment.   This lower unit is used for both the 2 stroke & the 4 stroke motors with most internal parts the same as the 74 - 93 models .  The 4 stroke motors that came out in 1995 & were a Suzuki powerhead but using the Bombardier lower unit.  

The gears, shaft & seals appear the same as the earlier versions as well as the water pump assembly.   The upper motor mount has been greatly improved as shown below.

Here is the improved upper mounting system

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 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.

The carburetor shown below looks externally very much like the pre 93's but internally the pickup tube & main-jet are simplified.   Notice the side located idle jet adjustment screw.   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.

On the plastic top & 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 & 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.  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 & 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.  The arm roller increased in size.

There is a slow & 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 & replace than the original steel roll pin.

Also there is a fuel bowl drain on the bottom RH side of the bowl & in the upper RH rear you will see the new idle adjustment screw, eliminating the idle knob off the front of the earlier models.

This Carburetor is off a 1994 9.9 Johnson

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 & 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.

The carburetor breather box has been changed so that the intake is buried underneath & now making it about impossible to squirt fuel into the carburetor to start a stubborn motor, unless you pull the breather box off.

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 & 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.  Tighten the nut enough to just squeeze the cable inside the plastic sheath.  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. 

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.

These 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 & eBay for some time & 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 & 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 & bending, more bending, installing & removal & 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 & 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 & 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 & 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.

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 & not rotate.

Left side lower cowling repair

One problem that has been encountered, is since the lower cowling is now plastic & the upper cowling is 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 rear plastic cowling latch.  This can therefore lead to latch breakage. 

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 & 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 rear cowling screw.   This makes it easy to inspect or clean it out if suspected debris may be plugging it .

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 & 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, & 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.

The neutral start override shown by the arrow.

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 & 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 & in alignment with the plunger lock, it then functions normally.   This just locks out the plunger lock from going inward & stopping the manual starter spool while in forward gear.