1986 Force 85hp Could Use Some Help

[jbwillis76]

Hi all! I've been lurking here for about a month and have been reading just about every post in the force section while I'm trying to get my first boat running. I will appoligize in advance for the long post, just want to be thorough.

I have a 1987 VIP 16' fish & ski with a 1986 Force 85hp outboard. Prop is a stainless 13x19. Here is what I've done so far.

Replaced fuel line, bulb and filter from the tank to the carbs.
Rebuilt the fuel pump
Replaced the water pump impeller

I've had it running for a month now. Cranks instantly and idles fine. Giving it gas it bogs and sputters. All this is on muffs, not in the water. Before I did anything else I wanted to get it in the water and see what REALLY needed doing.

I took it out yesterday and it cranked and idled fine. Putted around a little then I gave it WOT. After a good little while it finally planed out but my max RPMs are 2500. It ran at that max RPM for about 5 sec. then bogged out and would die if I didn't put it in neutral. If I put it in neutral it would run fine. I assume it's starving for fuel. I never looked in the tank and figure the pickup line or filter (if it has one) is plugged up.

I got it home and pulled the plugs (old ones) and the number 2 cylinder was clean. One at a time I checked for spark and all three cylinders where hot blue sparks. I checked the compression (cold) and they are:

1. 135
2. 135
3. 135

I was a little suprised by the numbers but VERY relieved.

Here is what I plan to do next.

Rebuild the carbs (one is leaking gas anyways)
Clean the tank.
Doing a link and sync (clymers manual) I know for a fact I'm not getting WOT at the carb. Butterflies a little over half way open.

Can anyone tell me why the 2 cylinder would be clean with spark and good compression? Also can you think of anything else I should be doing to get her running tip-top? And lastly for this boat and motor do you think it is over-propped?

When running it in the water yesterday It felt like it was running either on two cylinders or at half power. I'm hoping its just because the carbs need rebuilding and I'm not getting WOT. Any advise would be greatly appreciated.

Thanks for your time! James

 

[Frank Acampora]

Re: 1986 Force 85hp Could Use Some Help

First, I suspect that you were lucky that you could not get the engine running well: A clean plug would indicate insufficient fuel to that cylinder (assuming a good spark as you say). On a well running engine, this would lead to detonation and piston damage. Just for the hell of it, screw in all three low speed needles and count the turns. If that center carb is way less than the other two, then you know why the plug was clean. If not, check for a stuck float, inlet needle, or even a piece of junk that may have lodged in there.

SO: first set your synchronizing so that all three carbs open fully at WOT.
Check everything before the fuel pump for restrictions or clogs to ensure adequate fuel delivery--she sounds like she is running out of fuel as you suspect.

Then before you do any high speed runs, set the low speed needles on the carbs as per the manual. BUT REMEMBER: Do not set them leaner than 3/4 to 7/8 turns out. Then, set them on the water with full throttle acceleration as Clymers describes, but again, do not go leaner than 3/4 turn out.

Prop selection is not cut and dried from charts. You can start with an approximation but it always depends upon hull design and load in addition to size. That said, an 85 on a 16 foot boat under average load should not be overpropped with a 13 X 19 but even if it were, I would still expect to see at least 4,000 RPM. But after setting everything and getting the engine to run at full power, if your WOT RPM is not between 4500-5500, then try a 17 pitch prop.

 

[jbwillis76]

Re: 1986 Force 85hp Could Use Some Help

Thanks for the speedy reply Frank. I checked the low needle settings and they are all 1 1/4 turns out. I also checked the tank pickup and there is no filter on it and it is clean and gas pulls easily through it. I took off the line going to the carbs and pumped gas with the bulb easily. I then turned the motor over and very little gas pumped out. It was a steady stream but a very small stream. How much gas is suposed to pump out while just turning over the motor? A full flow like when I pump the bulb or more of a steady trickle? I did replace the fuel pump diaphram.

I'm waiting on some rebuild kits for the carbs, before doing the link & sync but did notice that I'm not even getting the butterflies half way open on WOT, which I believe to be most of my RPM trouble (that and the carbs need work). The "finger" from the cam touches the roller but doesn't push it any.

Thanks again for the help Frank.

James