won't accelerate after warmup

[MrWick]

I have a 1985 mercury o/b 115hp inline 6 that runs fine for about 5 minutes then when you push the throttle forward it just dies.It will start back up and will rev up fine in neutral but when you put it in gear it just bogs down.Took it out the next day did the same thing.It will set and run at high rpm's(2000 or greater)in neutral but when after it warms up it will not come out of the whole.Just won't accelerate after warm up but everything else seems fine,idled it in gear back to the dock and did not appear to miss at all.

 

[KCLOST]

Re: won't accelerate after warmup

Wick, I'm just asking this to eliminate possible causes.... <br /><br />This is probably the first question I need to check on, Are you sure you have the proper prop that is allowable on the motor?<br /><br />I'll ask more later...

 

[The Marine Doctor]

Re: won't accelerate after warmup

Check the compression and check the spark after the problem arises.<br /><br />TMD

 

[MrWick]

Re: won't accelerate after warmup

The prop appears to be the correct one,in the first 5 or 10 minutes the boat comes out the hole great,revs up to 5000rpm's at 44 mph without a problem.After 5 to 10 minutes nothing out of the hole,engine just dies.It will run all day at fast idle(2000)without a miss.Checked compression and all cylinders are 110-115 lbs.the engine will rev up to max rpm's even after it fails as long is it is not in gear and no noticable miss.

 

[MrWick]

Re: won't accelerate after warmup

I am not sure what my prop is,I have had it off looking for pitch and diameter but I cannot find anything stamped on the prop anywhere.It acts perfectly normal before it warms up so I would have to say it's a normal prop.It doesn't appear to be anything strange about the prop.

 

[thehound]

Re: won't accelerate after warmup

Is the primer bulb firm ? I had the same problem .<br />You might have a hole in the line from the tank to your fuel pump , dirty fuel filter or fuel pump needs a rebuild .<br />You probably get your boat going by slowly priming the bulb while someone advances throttle<br />The Hound

 

[MrWick]

Re: won't accelerate after warmup

The primer bulb is new and it appears to stay firm and the filter screen was removed and cleaned but it looked pretty good when I removed it the first time.Primer bulb and fuel line from tank to engine are new.Spark plugs are new also.

 

[The Marine Doctor]

Re: won't accelerate after warmup

One or more of your ignition components is falling on its face when it heats up.<br /><br />TMD