1989 Force 85 stalls at full throttle

[thimsllib]

Motor idles fine. When I get her out to the bay and hit the throttle the boat planes off great. I don't have a working tac, but using GPS I hit full throttle at roughly 27MPH and then the motor dies. I'm able to start right up again and plane off again, but when I hit full throttle it stalls again. Always between 25 and 27 MPH. (Capri 1700). Never any issue starting back up.

I just took apart, cleaned and rebuilt all 3 carbs. Also replaced the 3 check valves in the fuel pump as well as the diaphragm and gasket, and the reed valves looked great, so I don't think it's a fuel delivery issue. Battery was reading 13.4 volts when planed off, so I believe the stator is working fine. Has anyone ever had this problem?

Any help would be greatly appreciated. Thanks.

 

[foodfisher]

Re: 1989 Force 85 stalls at full throttle

Check for a wire that's rubbed bare up around the flywheel. The ones that move when the timing is advanced.

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

That makes sense. I'll check that out. Thanks.

 

[sho3boater]

Re: 1989 Force 85 stalls at full throttle

Also look at your fuel vent and/or pickup for the tank.

 

[moparman]

Re: 1989 Force 85 stalls at full throttle

Was it doing this before the carb rebuild?

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

Yes, before the carb rebuild, it did do this... here's the history:

Bought the boat from a guy who let it sit in his yard for 2+ years. He couldn't get the motor running.

Got the motor running, dropped it in the water. Had trouble idling. It would stall at low idle and I had to quick throw it in FWD to get her going. Got it to plane off, hit 27+ MPH and it went dead. Limped back to shore.

Adjusted the idle and choke, put it back in the water and lost power after a few minutes. Had to get towed in. That's when I did the carb/fuel pump rebuild. Definitely felt like a fuel starvation issue. I also pumped out the gas tank and refilled it with fresh gas and a bottle of dry gas.

Now she starts right up, idles good, planes off fine and when I get her up to full throttle, she dies on me. Next step I plan on checking the wires under the flywheel, as recommended above, and hooking up a temp tank with fresh fuel and running it to see if it could be a problem with water in the tank. I'm also going to decarb with seafoam.

Anything else it might be?

 

[moparman]

Re: 1989 Force 85 stalls at full throttle

Still sounds like a fuel problem. Might want to pull the pump and check the diaphragm to see if it got wadded up around the screw holes and make sure the valves are in the right way, I've came across a couple that had just had the diaphragm and valves replaced ,and one of the valves was in backwards,its so easy to do.

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

I checked the wires under the flywheel and they're all good. Also hooked up a temp tank with fresh fuel and it was still happening, so ruled out water in the gas, or a vent/pick up problem. The fuel pump diaphragm and check valces are brand new and I double checked the Seloc manual to make sure they were in correctly, and they are. It definitely seems like a fuel starvation problem at high RPM's, which I would think is a pump issue, but everything in the pump is new. What else can it be? I'm stumped.

By the way, when I was out over the weekend and she started to stall at high speed, I pumped the ball and it kept running. How come not enough fuel is getting to the cylinders at high speed?

 

[foodfisher]

Re: 1989 Force 85 stalls at full throttle

Sticky float/needle valve? Air leak?

 

[further]

Re: 1989 Force 85 stalls at full throttle

My 1988 85 HP is at the shop - having the same issue now after a carb rebuild. He's checked everything out - fuel pump good, carb adjustments good - starts and idles great, but he had it out and after a while at WOT it stalled. bottom two plugs were fouled. He is thinking that it is the fuel recirculation screen and assembly that may be plugged. I've heard of this happening before where the orifices where the lines connect to get plugged up and affect performance, so he's getting some new gaskets and new screen to see if that works.

 

[sho3boater]

Re: 1989 Force 85 stalls at full throttle

There is also that orifice for the intake oil, at the bottom of the carb intake cover. But I've never heard of that killing the motor but who knows. I've never cleaned mine just a squirt of carb clean in it. Mine ran great last weekend until the prop near fell off....watch that nut. I lost the plastic diffuser ring not found another yet. It wants to cavitate more without it and the steering torques.

 

[moparman]

Re: 1989 Force 85 stalls at full throttle

have you rechecked the pump diaphragm? Its easy to get the gasket wadded up around the bolts as your installing it . Just a thought

 

[john from md]

Re: 1989 Force 85 stalls at full throttle

Replace the three check valves in the fuel pump housing as they are sticking.

John

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

I'll take a look at the fuel recirculation screen and assembly.

Further - Can you keep me updated on what your mechanic finds? Striper season is coming quick.

John - I just installed brand new check valves. Verified that they were installed correctly. Do you think they can be sticking? This happened on the first run after I installed the new ones. Thanks all.

 

[john from md]

Re: 1989 Force 85 stalls at full throttle

If they were new valves, the new material won't expand with the alcohol. If the poppet material was grey or black, it is the new material. If it is clear or amber, it is the old material.

If the lower plugs are coming up black, you for sure have a rich burn. If your engine did any backfiring after the fuel pump was installed, it could have popped a hole in the diaphram. It will still run with a tear but will not run correctly depending if the tear is in the first stage or second stage of the pump. It's only six screws to take out and check.

The only other thing I could think of is that the floats are set too high.

How long does it take after the throttle goes to WOT for the engine to quit?

John

 

[further]

Re: 1989 Force 85 stalls at full throttle

Will let you know Thimsllib when i hear. Still waiting on the parts - another weekend without the boat and the season is quickly approaching its end

 

[john from md]

Re: 1989 Force 85 stalls at full throttle

Further,

Don't worry about those stripers. They will be making their way south to the Chesapeake and I will take good care of them for you.

John

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

John... thanks. The check valves are gray. Just bought them from Cowley Marine. Haven't pulled the bottom plugs. I'll pull them when I pull the pump off to check the diaphragm (which is also brandnew).

Engine quits after about 20-45 seconds of WOT

Occured to me yesterday.... the primer bulb stayed deflated when I pumped it while the motor was running. I don't think that's normal... should've filledright back up,right? Is that a vent problem? Could this whole thing be a clogged vent?

 

[john from md]

Re: 1989 Force 85 stalls at full throttle

You can have a clogged vent or a bad check valve in the ball, or something obstructing the inlet. It should always come back up after it is pumped.
Start with the easy test; open your fuel tank cap and see if the ball inflates.

John

 

[thimsllib]

Re: 1989 Force 85 stalls at full throttle

Is 1/4" fuel line enough to sustain an 85 HP at full throttle?