Military Outboard OMC 35hp

[baconbiscut]

It's been a while since I've posted here but I picked up a 35hp OMC Military outboard today. The model number is 1081-001A. It has a dewatering system that I've never seen before and it's missing the nob for it. What I'd really like to know is how the dewatering system itself works. Also I can't seem to find a good source for parts. If anybody has any info/experience with these engines I'd love to hear about it.

Dan

 

[jimmbo]

A lot of Miltary engines were expected to be used after even prolonged submersion, many were equipped with Check Valves in the Exhaust that closed when the engine was upside down on it Cowl, they also had Quick Drain Systems for evacuation the Carb and Crackcase of water.
Finding Service Manuals for these engines in not easy, maybe the Military in all its Stupidity/Jugheadedness, thinks as these as Secret Covert Weapons.
The Dewatering/Drains should be pretty straight forward if you want to remove/disable it, though it is a great way to drain the carb for storage. Any Valving in the exhaust, if it has that, might be a little more fun

 

[baconbiscut]

I took it out for the first time today it runs well. It’s on a 14ft V-hull Mirrocraft. The dewatering valve has a bunch of
lines running from it to the carb, the choke also seems like it some sort of primer as well. Since the engine runs well I think I’m just going to let sleeping dogs lie. When it comes to normal maintenance, plugs, water pump, carb kits, and ignition. Is there a civilian model I can use as a reference to order parts?

 

[jimmbo]

That is where it can get a bit complicated. While some parts are unique, the majority will be standard OMC 35 hp parts. But there were many subtle changes to the 35 hp thru the years. So picking the civilian model closest to what you have will take some sleuthing

 

[JimS123]

Here's what a google search came up with. Looks like its compatible with a 1984 Johnson or Evinrude.

Motor Description Make Model serial Year HP: [FONT=Trebuchet, Trebuchet MS]1984 Johnson ( evinrude ) 35 hp MARS h[/FONT]
1984 Johnson 35hp Model #AM35B-1 Outboard Engine,MARS(these motors were used for military use(marine))
NCSC spec 1081-001A
NSN 2805-01-118-1275
contr.N61331-84-D-0047
Serial E 6260902.
Shaft size:
What start: pull
Compression:
Gearcase oil condition: clean
All parts work and in good condition unless its described above.
All parts needs to be cleaned.Cant guarantee that seals,gaskets or rings are good.

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.

 

[baconbiscut]

Thanks for the help guys, I’m gonna go with 1984. The knob for the dewatering valve is missing. On the hood it says don’t run for prolonged periods of time with the valve open. I have no way to confirm whether it’s open or closed. I could start dissembling the dewatering system to see how it works and verify that it’s closed and then leave it inoperative. I’m a little hesitant to do that though on an engine that otherwise runs perfectly. Any thoughts?

 

[JimS123]

I don't know, but maybe if you don't throw the motor under water it won't matter if the valve is open or closed.

Ask your questions over at AOMCI. If they don't know, nobody will.

 

[baconbiscut]

Update. I still have this motor and it runs well, I just replaced the propshaft seals and rebuilt the carb I do have a problem though. It runs well and it starts on the first pull almost every time however it dies after about thirty seconds then I have to re-prime it using the bulb then using the choke/primer set up. I start it again and run it at high idle then it runs and trolls fine all day. If I stop the motor at any point for more than 15 mins I have to repeat the process. I have it down to a science at this point so it doesn't bother me much but I'd like for my old man to be able to use this motor reliably as he's not mechanically inclined and its a lot of motor for him to pull over. I'm thinking it's possibly a weak fuel pump but maybe it's some sort of lose connection between the primer and the carb that's allowing air into the system. I figured I'd ask the experts here before ordering a rebuild kit for the the fuel pump. I hate to just throw parts at something unnecessary.