Maintaining Johnson/Evinrude 35/40hp outboards

1965 - 1977 & on,   (Information & Observations)   

This Family of OMC outboards were pretty popular, ran quite well, had lots of power, however the early models  were rather thirsty motors.  My experience is that they were rather easy to work on.   And when set up right, they were easy to start even using the manual rope starter.

On the early motors, there was no charging coils under the flywheel, but used a separate belt driven generator and a voltage regulator for 12 Volt power.

Carburetors used on the early motors had both a adjustable main and idle jet accessible from the front thru a hinged door.

Lower units on the early motors were the non-thru the prop exhaust type.

1971 40hp Johnson fitted with a outboard jet  


These motors shared many parts and were just larger powerheads than the 15-18hp series as seen below.

The 15's were originally built by Evinrude from '53 on to '56 and had 19.94 CI.   An excellent improvement over the 14's of 1950 and 51.    The FD/Fastwin was even more improved in 1957 as an 18. For 1957 the FD series was bumped up to 22CI. in the 18HP FD-11. This 22 cube design was actually the base design for two more models up until 1976.

An 18hp powerhead should mount on the 15 midsection though and work fine, since this part was the same, from 1956 - 58. 

The 22 cubic inch motor continued to be made as an 18 hp by Evinrude and the 20 hp by Johnson. 

In 1974, the same motor was again modified to produce 25 hp, from the same 22 cubic inches, and sold along side the 18 - 20hp.  Carburetion being the main improvement.

The 20hp of 1966 and the 25hp of 1969.  One of the best designs ever built by OMC.

The reliability is good in all the years that they were built (1957 - 73) but after 1958, when they went to that fiberglass hood set up, that was the only drawback. Those little rubber shroud mounts usually are broke, and if you decide to grab the fiberglass lid to beach the motor?   HAH!  You only end up with a lid in your hand.  The best 18's were built in '57 and "58 with the good old aluminum clamshell covers.   No plastic parts and they were tough as bullets.

In the late 1970's the 22 cubic inch motor was dropped, and replaced by a much different design making it a 35hp.  The 35hp was detuned to make several versions producing 20, 25, 30hp.  But not the same motor as the old 22 cubic incher. 

           35hp Johnson Lark showing the flywheel being pulled with a puller & strap wrench around the starter gear teeth.  The upper "gear" is used to drive a cog belt to a generator, if so used.

In the photo above you can see the smaller center cog gear.  This was to drive the generator if that motor was fitted for one.  The small plate on the top of the drive gear that is held in by the 2 screws is an inspection plate giving access to the points.

Electric Start/Charger ;   These early motors could have had a electric starter with charging capabilities.  The voltage regulator was usually mounted in a separate box away from the motor.  On the motor shown above, it was equipped with a tiller handle and not a lot of room for a tidy installation of a remote type regulator.  I took the generator to a farm tractor repair store that also dealt with older "antique" tractors.  He took the output information of the generator, cross-referenced to a transistorized regulator that was compatible and yet a lot smaller that could be mounted inside the motor's cowling.   Not cheap, but it works.  To keep from loosing it's identity, I wrote the info on this regulator.

           1971 40hp Johnson fitted with a transistorized voltage regulator
Electric Starter/Kill Switch ;   On these or even the smaller older motors, especially those using remote start, finding replacement ignition switches would probably best be aftermarket ones.  There  are 2 styles, (1) with a push to choke and (2)  the other without.  However you might as well buy the one with, and since you may not need the electric choke provision, just not wire in the extra connection.   Here you can go to NAPA Auto Parts and ask for marine ignition switch #18-1802 (which replaces OMC's #393301 and #508180).

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Originally started 4-02-2011, Last updated 08-28-2017
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Army issue Evinrude 35hp

I just got an army issue 35hp evinrude. I am trying to figure out what year it is. on the motor it reads:

NSN: 2805-01-118-1275
Contr. N61331-84-D-0047
MFR. outboard marine corp.
Serial no. E-6260587
To break that down some for you:

NSN (National Stock Number), It's a number assigned to anything that becomes available through the military/gov't supply and logistics system.

Contr. (Contracter #, or Contract #), this was the number assigned to OMC by the gov't or the Contract # under which a whole pile of outboards were purchased under.

MFR (Manufacturer), OMC, self explanatory.

Serial #, also self explanatory.

Right now the upper is painted OD green, and the lower is black. Looks like the military could have done this.

I'm willing to bet, that the lower unit is different in design. I seem to recall having a 25hp that was a little bit earlier than this and the drive shaft had multiple splines, versus the typical 4 splines.

Thanks, I found the welch plug. it says AM35B-1, so according to the website below, it is an '85 or '87.

I just looked at that too. I am inclined to think that you have an 85. The 87 would be AM35BI.

The difference between a Military and civilian 35 is that the military version has a de-watering switch with hoses attached to the intake, carburetor, and bypass cover. The motor can be submerged up to two atmospheres, 66 feet. Once on the surface the de-watering switch is pulled out and the pull cord is pulled 8 to 10 times to expel any water. The dewater switch is closed and the motor is cranked.