89 mercruiser 305 chevy bogs when warm

[kencobia]

help,my mercruiser runs great when first started runs good for around 15-20 mins then at 3/4 or better throttle bogs and restarts runs then dies then will not restart for a while.seems like fuel problem.replaced fuel water seperator, fuel filter in carb,cap,rotor,coil and fuel pump.same problem.after cools starts and runs next day.same symptems after 15-20 min running fast.spray carb spray in carb starts until burned up.what next?

 

[searay_89]

Re: 89 mercruiser 305 chevy bogs when warm

Did this just start happening??<br />Give more detail<br />Are you using a different brand of gas?<br />Read my posts - different engine but same type of problem - replaced everything - same as you.<br />Can't seem to fix it

 

[SeaSkwurrel]

Re: 89 mercruiser 305 chevy bogs when warm

I would rebuild the carb next. I'd be suspicious of the accelerator pump having problems. Also, check that the choke plate is working properly. You could be getting a flooding condition due to internal carb issues.

 

[Joenic]

Re: 89 mercruiser 305 chevy bogs when warm

Since I know Ken and the boat, I'll try to answer any questions till he is back on the board.<br /><br />This boat is new to him, and has acted this way from the start. I too was thinking about the accelerator pump, but why would it start acting up after being run for 15 minutes.<br /><br />How about vapor lock? Any way to diagnose that?<br /><br />Thanks.

 

[Haut Medoc]

Re: 89 mercruiser 305 chevy bogs when warm

I would see if this condition persists when you run without the gas cap on. A plugged vent line can cause this symptom.......J

 

[Haut Medoc]

Re: 89 mercruiser 305 chevy bogs when warm

Oh yeah, theren=is a screen at the bottom of your pick-up tube that can get slowly clogged from the suction of the fuel pump. When the vacuum quits after the engine dies, it is able to get suffecient flow again. I think you have a venting/suction problem, the heat part is just coincidental........J

 

[Richard Petersen]

Re: 89 mercruiser 305 chevy bogs when warm

+ 15 minutes puts us squarely in heat build up of fuel or ignition. Can you run steady below the bog? How long? Wild a## guess, ignition is conking out when heated up. You did not change the capacitor ?

 

[Joenic]

Re: 89 mercruiser 305 chevy bogs when warm

Ken, any updates?

 

[kencobia]

Re: 89 mercruiser 305 chevy bogs when warm

I spoke to a boat repair specialist and he suggested the check valve in the fuel pick up may be gummed and sticking.I will keep posted ,I am on my way to look at it now thanks