50HP 1988 Force outboard

olsenk514

Seaman
Joined
Sep 3, 2009
Messages
50
Hi Everyone...This is my 1st post on this forum, although i've been reading it for several weeks. You guys have some great information on here...

Anyways, I'm stumped here. A friend of mine recently gave me a force 50HP outboard...model 507F8D. It runs alright once i get it started, but it idles pretty rough. It takes quite a few cranks to start also.

I pulled the carb apart last night, thinking the jets were clogged which would explain the rough idle -- The thing was clean as a whistle. I soaked the jets in gumout for about an hour and cleaned everything else as well. put it all back together and it's the same thing. It'll start eventually but when I try to idle it will die. I've reset the idle needle to factory specs (1.5 turns from light seat) and tried making adjustments to that.

Now the thing that gets me here is I did a compression test and both cylinders only made it up to about 40psi???

How is it even possible that this thing is running on 40psi? I pulled the head off and looked at the cylinder walls and they seem to be fine. The head gasket looks fine too. I would suspect something was wrong with the test but i tried my bike right after and got in the 150's.

I dont want to spend alot of money on this thing, but i dont want to just get rid of it because it runs alright anywhere from fast idle to wot.

I'm going to try to decarb the pistons tonight and see what happens.

Any help or suggestions will be greatly appreciated.

Kevin
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 50HP 1988 Force outboard

I'll bet that it's the rings. They're probably frozen in the ring grooves from carbon.

You can take one of the by-pass port covers off and look directly at the rings on the pistons through the by-pass port holes in the side of the cylinder. They should move freely. They won't spin around on the piston though because they are pinned to prevent that.
 

olsenk514

Seaman
Joined
Sep 3, 2009
Messages
50
Re: 50HP 1988 Force outboard

Did a decarb last night with seafoam...I started it up this morning and it seems to run much better and will idle lower. I think i'm going to do another round tonight and see what happens. Did a quick compression test and it came up from 40ish to about 90-100. Seems like a significant improvement. I guess the motor's been sitting a while...i'm assuming the piston rings were stuck.

Is it possible to hurt the motor by decarbing twice like this?
 
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