1990 Force 50 horse run issue

[biga38501]

1990 Force 50 horse runs ok untill the engine warms up.
Engine runs about 5 mins and at this point we lose the top end(high rpm and speed), it also will not idle, it dies when you try to idle it. Like running half speed with no idle.
Also appears to misfire at times.
If you shut the engine off and allow it to cool down (5-10 mins) it will run.Then we start the entire process over again after running for about 5 mins.

Previous repair history in last year( head gakset, water pump, thermostat, spark plugs, temp sensor, rebuilt carb, removed all old fuel and installed new)

Any ideas?

Any and all help is appreciated!

 

[jerryjerry05]

Re: 1990 Force 50 horse run issue

Do a compression/spark test.then rebuild the fuel pump.
You running it in the lake or the drive?? The muffs you use could be the wrong ones.The right are in the pic I added.
Check the impeller.Sounds like it's overheating.J

 

[EverydayAngler]

Re: 1990 Force 50 horse run issue

could be a stator going too. when it heats up it opens a winding in the coils on the stator.

 

[biga38501]

Re: 1990 Force 50 horse run issue

We have checked both compression and spark. Also checked timing. We are test running this boat in the lake. Any good way to check to see if fuel pump requires rebuilding?

Also any idea on how to check a stator?

 

[bentle]

Re: 1990 Force 50 horse run issue

If you give the primer bulb a squeeze after it starts to bog and it picks back up then you need to rebuild fuel pump. If the primer bulb goes flat while it bogging down then check fuel pick up tube in the tank and make sure fuel vent is not plugged.

 

[biga38501]

Re: 1990 Force 50 horse run issue

We have given this a try and the bulb stays firm the whole time. Also no pick up in engine rpm when squeezing the bulb.

Any thoughts on module(switchbox), coils, stator.

If you give the primer bulb a squeeze after it starts to bog and it picks back up then you need to rebuild fuel pump. If the primer bulb goes flat while it bogging down then check fuel pick up tube in the tank and make sure fuel vent is not plugged.

 

[bentle]

Re: 1990 Force 50 horse run issue

Have you done a spark test with the in line see through spark testers after motor is warm
and starts acting up? The symptoms you described would suggests a fuel related problem but I have heard of coils shorting out after warm up and producing the same symptoms. Have you checked all ground wires and positive wires for good connections? Try running motor with the top cowl cover off to rile out an exhaust leak. Or check exhaust plate for any loose or missing bolts. 70 inch pounds on those bolts . Any more and you will strip the aluminum threads.

 

[mrdibs1]

Re: 1990 Force 50 horse run issue

It's probably overheating, or not getting enough fuel. If it's running too lean, plugs will turn white. If the motor doesn't have a tell-tale, check the sticky for how to install one. Will make you feel better about cooling.

 

[biga38501]

Re: 1990 Force 50 horse run issue

I have checked the spark when the engines warms up and it never lost spark. I checked the exuast plate today at lunch for any loose or missing bolts and found none. I have checked and double checked all the wires and connections and have found none broke or any loose connections.
This motor does have the tell-tale and an overheat buzzer. The buzzer has not came on and the water is coming out of the tall-tale like it should.
I really like our fuel supply is what it should be
Has any one seen a switchbox or stator give this kind of trouble before
Thank you for all your help

 

[bentle]

Re: 1990 Force 50 horse run issue

If the stater was your problem then you would be getting a weak spark after warm up. What is your timing set at? Static time should be set at 30?btdc & 32?btdc with prestolite magneto cd ignition. Have you also checked the fuel return system on your motor. If this gets clogged then it will it can run the way you described.