POWER LOSS FORCE70HP

[imported_BABOONBUM]

MY 1993 70HP FORCE WAS GOING GREAT LAST TRIP BUT ON WAY HOME WAS CUTTING OUT WHEN I ACCELERATED,IT GOT ME HOME BUT PULLED LIKE IT WAS ONLY FIRING ON 2 CYLINDERS WHEN I PUT THE THROTTLE ON FULL IT WOULD GIVE ME A BURST OF SPEED AND THEN DIE,IV FITTED A NEW STATER LAST YEAR AND NEW PLUGS,I GET A SPARK AT EACH PLUG ON ALL 3 CYLINDERS WHEN ON DRY LAND WHEN I TURN THE ENGINE OVER IF I REPLACE THE SWITCH BOX WOULD I BE BARKING UP THE RIGHT TREE (THEY ARE EXPENSIVE?)

 

[Koda]

Re: POWER LOSS FORCE70HP

I am no outboard expert but sure sounds to me like it may be a fuel problem, if you let it idle for a bit then kick it wide open and it runs for a bit could be fuel problem, have you tried pumping the fuel bulb when this happens? Luck David

 

[roscoe]

Re: POWER LOSS FORCE70HP



Welcome to iboats.

Do not throw parts and money at the problem.
If you can't confirm an ignition problem, and isolate the offending component, then don't mess with the ignition.
Identify the cause.
spark?
Compression?
fuel?

Then pinpoint the problem.

It could be something as simple as a failing fuel pump. a cracked hose drawing in air, or wire that is grounding out due to cracked insulation.


So, did the fuel line bulb go flat when this happened?
Did it develop an obvious miss, or just go weak on power?


Firing on 2 cylinders shouldn't give you an initial burst of speed.

I'm with Koda, sure sounds like fuel system problem to me.

Go through the system, put a new filter in, put a new diaphram in the fuel pump, inspect all hoses for cracks and leaks. And use a different (portable) fuel tank with fresh fuel.

Take the boat for a run, squeeze the primer bulb when the engine is faltering and note the results.

Let us know what you find.

 

[AlanR]

Re: POWER LOSS FORCE70HP

id runa compression test. Cheap, easy and quick to do (if you got the tools)

 

[harkawy]

Re: POWER LOSS FORCE70HP

When was the last time the fuel line and bulb pump, from the tank to the engine was replaced?

I had a similar problem after I purchased my new (used) boat. It started great. It ran great. Just after noon, I would start it and "no wake" it to open water and then it would die and would not re-start. More than once I had to be towed back to the dock.

It seems that the bulb primer pump or fuel line near or below the pump may have had a very small hole permitting air in the fuel line. As the heat of the noontime sun heated the pump and fuel line it/they expanded permitting air in so the fuel drained back into the fuel tank. There was sufficient fuel in the carburator and fuel line above the bulb to start and idle the engine but after a few minutes it basically "ran out of gas." I had the fuel line and bulb replaced.... No more problems!

I hope your problem is as easy to fix....

 

[SCO]

Re: POWER LOSS FORCE70HP



I am having the same problem. I could run great for 30 seconds then power loss..3500rpm max. Hitting the throttle more resulted in slightly more power ..working the engine. I could throttle down to idle for 30 seconds and then all would be fine for the next 30 seconds. Conclusion is that one of the 3 carbs is fouled, probably the float valve which cannot fill the bowl fast enough to keep up with demand or maybe a clog in the line to one of the carbs. Pumping the bulb wiould barely allow me to keep the motor running but immediately on release it would go into 2 cylinder mode. I could not "refill" the bowl to get another 30 seconds of good run time.