1989 Force 50 won’t idle after engine warms up

[Wcbond4]

507X9C

Just bought this old boat. Engine starts up very easily and will idle, but after getting up to operating temp, it won’t idle. When trouble shooting in the barrel, it also has sluggish throttle response time after being warm. Too much throttle too fast will kill it.

I did some initial diag and found that I wasn’t getting any spark on the top cylinder. Changed plugs and the coil for that cylinder.

Rebuilt fuel pump

New gas and oil in the tank

New battery

Supposedly the carb was rebuilt by the guy I got it from. For the fact that it idles correctly when cold makes me think it’s not a carb issue. The bogging under throttle makes me think it could be though. Possibly these issues are related but maybe not? Could be two different issues. Could my other coil pack be weak and I’m not getting adequate spark after it’s warm?

Any guidance is appreciated.

 

[racerone]

Open slow speed mixture screw 1/8th turn at a time and test run.

 

[jerryjerry05]

Do the starting fluid test: start the motor, spray SF around the intake side of the engine. If that makes the motor run different?? Then it's sucking air and needs to figure out where?
You have 2 port covers on the intake side. One has the fuel pump the other nothing. Most time the port caver gaskets can blow and the motor sucks air.
One TINY!!!! backfire/ cough/ stutter can blow one of these gaskets.

 

[Wcbond4]

Do the starting fluid test: start the motor, spray SF around the intake side of the engine. If that makes the motor run different?? Then it's sucking air and needs to figure out where?
You have 2 port covers on the intake side. One has the fuel pump the other nothing. Most time the port caver gaskets can blow and the motor sucks air.
One TINY!!!! backfire/ cough/ stutter can blow one of these gaskets.

Spraying this gasket in the rear killed the engine.

 

[Wcbond4]

Open slow speed mixture screw 1/8th turn at a time and test run.

Is that the brass screw above the intake on the end of the carb?

 

[Wcbond4]

Spraying this gasket in the rear killed the engine.

I guess I’m referring to the head gasket.

 

[cyclops222]

The selling of old, run ito the dirt, boats and engines, with NO maintainance should be illegal !!!

WE kill, destroy useless horses. Why not boats also ??

 

[Wcbond4]

The selling of old, run ito the dirt, boats and engines, with NO maintainance should be illegal !!!

I got a fair deal on it and I they told me they couldn’t figure out the idle issue. I’m just a glutton for punishment.

 

[Wcbond4]

Do the starting fluid test: start the motor, spray SF around the intake side of the engine. If that makes the motor run different?? Then it's sucking air and needs to figure out where?
You have 2 port covers on the intake side. One has the fuel pump the other nothing. Most time the port caver gaskets can blow and the motor sucks air.
One TINY!!!! backfire/ cough/ stutter can blow one of these gaskets.

Also possible that the port cover is causing it as well. I sprayed all around the gaskets below the fuel pump and it also died then too

 

[jerryjerry05]

Sounds like the starting fluid test might have found the problem?

 

[Wcbond4]

Sounds like the starting fluid test might have found the problem?

Possibly. My new gaskets just came in today. I’ll be installing and testing this week.

 

[kalebsheridan]

How'd it turn out? I have basically the same motor so I'd like to know in case this happens to me.