1996 75 hp force running poorly

[spooly]

ok guys...this is my first post so bear with me...1996 75 hp force runs but runs poorly...135# comp.on all 3cyc.,checked fire with sparky tester with all 3 firing with good blue spark,pulled and cleaned carb with berryman chem-dip cleaner,installed new ngk plugs...engine will crank but as i pull each plug wire with engine at an idle on muffs pulling top plug wire engine dies,replace plug wire re-crank engine pull # 2 engine keeps running,pull # 3 and engine keeps running...so it sounds to me engine is only running on # 1...with fire,comp,fuel whats going on here...HELP

 

[Jiggz]

Re: 1996 75 hp force running poorly

Assuming your diagnosis of spark and compression is accurate. That means it will have to be a fuel problem. Check the idle mixture screw settings on #2 & #3 cylinders to make sure they are set right. For now turn them clockwise (CW) until lightly seated. Then turn it back CCW 1 1/4 turn out. Do this on both cylinders. Try again and if the problem persists, get a spray bottle with fuel-oil mix and spray it directly into #2 or #3 cylinders and listen for change in engine tune. If the engine tune changes for the better then it is a fuel delivery problem.

Verify there is fuel in the carbs (#2 and #3) bowl by loosening the bottom screw and fuel should start leaking. If there is no fuel, then remove the bowl and check the float settings and the needle valve. While at it, remove the idle mixture screw all the way out and then shoot carb cleaner into the port. Check make sure the needle screw is not worn out (should be smooth conical needle). Replace needle screws and set as mentioned above.

Repost your result.

 

[spooly]

Re: 1996 75 hp force running poorly

thanks for reply,but the 96 force 75 hp is a single carb,still scratching my head on this one

 

[roscoe]

Re: 1996 75 hp force running poorly

I would remove the carb again, and inspect the reed valve petals.
If several are broken, bent, or obstructed by foreign material, it will cause symptoms you described.

Do you have any history on the engine?
Has it run well in the past?
Or did you recently buy it?

Welcome to iboats spooly.

 

[TwoFish]

Re: 1996 75 hp force running poorly

I have a 1998 75hp with a miss. Stripped it down and found a few problems. The reeds did not close properly and needed replacing. The gasket in front of the reeds, on the intake manifold was split. The check valves for the recirculation system weren't working. All easy to check.

Have you checked the fuel pump for a split diaphragm? It can leak uel into the crankcase.

 

[spooly]

Re: 1996 75 hp force running poorly

last time i pulled carb i looked at reed valves...well as many as i could see that is...might need to remove intake to get a better view,pulled fuel pump when removed carb and inspected with no visual problems,will take off and inspest check valves asap...thanks for replys...thought i would check the ohms on stator just to make sure...i guess the stator could be breaking down under load...just a thought

 

[TwoFish]

Re: 1996 75 hp force running poorly

My reeds looked ok when looking from the outside. The allowable gap is quite small and only visible when removed.

The other thing I found was a break in the insulation on the main battery leads. It was right where they enter the cowl at the front of the motor. A stress spot from tilting the motor and not visible until I removed the leads. It was the negative lead and the wire inside had a fair amount of corrosion. Not sure if it was part of the miss but it made the starter work slowly. I'm having a new motor fitted to the boat so I'll never know what caused the problem.

 

[Jiggz]

Re: 1996 75 hp force running poorly

thanks for reply,but the 96 force 75 hp is a single carb,still scratching my head on this one

My bad, I was thinking about the 85!

 

[Jiggz]

Re: 1996 75 hp force running poorly

last time i pulled carb i looked at reed valves...well as many as i could see that is...might need to remove intake to get a better view,pulled fuel pump when removed carb and inspected with no visual problems,will take off and inspest check valves asap...thanks for replys...thought i would check the ohms on stator just to make sure...i guess the stator could be breaking down under load...just a thought

You should be absolutely clear with your diagnosis so as not to end up going in circles. With a spark tester be 100% sure you have good sparks on all 3 cylinders both in idle and high revs. Then you can just focus on air-fuel delivery problem caused by faulty reeds, fuel recirculation or recovery system.

Another diagnosis you can do is increase the idle mixture setting to about 1 1/2 from lightly seated. Run the engine for half a minute while raising the the rpm to about 2000 RPM. Shut down the engine with the engine at 2000 RPM without lowering RPM or coming back down. Remove spark plugs from #2 and #3 cylinders and check for wetting in the plugs. If the plugs are wet with fuel and oil, the problem is not fuel delivery problem but more of spark problem. If they are bone dry, then it is fuel delivery problem assuming the engine was still missing at 2000 RPM. But if the engine is not missing at high RPM, you might just need to de-carbonize the engine. Don't forget to reset the idle mixture screw.

 

[spooly]

Re: 1996 75 hp force running poorly

ok guys found it...ya'll were dead on...broken reed valve and one bent...thanks for all your help...gotta get em ordered...thanks again