Motor runs out of fuel at full throttle

[madripor]

My father owns a 1977 mercury 1500.

When at full throttle the motor runs out of fuel. The RPMS drop to about 3500 then it revs back up and down again.

We have Rebuilt the fuel pump, checked all fittings and lines for leaks, fuel at all carborators, and also decarbed it.
When pumping the bulb the engine will stay at full throttle

Any suggestions or helpful things to looke for to keep the motor running at fuel throttle without dying out?

 

[Texasmark]

Re: Motor runs out of fuel at full throttle

You just answered you own question. "pumping the bulb will cause it to stay at full throttle". You have a supply problem. Clogged filter in the fuel line (in the tank or between the tank and engine) or crud from anti water agents; or possibly a clogged fuel cap vent or some other valve that Dan Haley knows about.

Mark

 

[tashasdaddy]

Re: Motor runs out of fuel at full throttle

does it get to full throttle and run a while and then start to die, or does start to fully throttle and never make it. these can be two different things.

 

[madripor]

Re: Motor runs out of fuel at full throttle

It gets to full throttle, then cuts off and drops to about 3500...then revs back up again to full, then cuts off, and drops

 

[andy6374]

Re: Motor runs out of fuel at full throttle

Sounds like an ailing fuel pump. When was it last rebuilt?

 

[tashasdaddy]

Re: Motor runs out of fuel at full throttle

rebuild fuel pump. if hoses have never been replaced, replace, vent open on gas tank? that will starve it of fuel also.

 

[boat anon]

Re: Motor runs out of fuel at full throttle

just cleaned out my tank this weekend after a 4 week hunt trying to figure out why my boat was sluggish (1st only at WOT, then wouldnt start for a few mins)....

55 gal alum tank was below all the wood i just fiberglassed, i cut a 5"x5" hole in it and drained the tank with an electric fuel pump hooked up to a portable battery charger through the fuel sender hole. the i took a dyegrinder and ran it under water while i cut thru the aluminum. aluminum will NOT SPARK. so put all those myths to rest. the only reason i ran it under water was to keep it from getting too hot.

there was a pile (3 full hand-fulls) of sludge, dirt, sand that was clogging the pickup tube that goes to the fuel pump...i replaced 3 electric fuel pumps, the carberetor, the fuel filter before i realized that this was the problem.

i sealed it back up with a alum plate and sealant and the boat is running PERFECT.

just letting you know, in my case, flushing with alcohol wasnt enough.