83 merc 150hp bog down

[inlgmouth]

My boat bogs down and dies when going to WOT. If I hold choke in it will take off. Last summer fuel pump was rebuilt as well as carbs. I rechecked float settings after the problem and they were ok. Anyone know what I could be missing? Thanks

 

[Laddies]

Re: 83 merc 150hp bog down

Make sure the timing is retarded 2 degree from stock and pull the back drag jets out of the carbs, then remove to high speed jets and make sure they are the proper sizes and clean them. Other than those problems the carbs could have trash screens still in the carbs they were right behind the inlet elbows and get junked up over the years if not removed.

 

[Chris1956]

Re: 83 merc 150hp bog down

that is the classic example of the idle mixture being set too lean. If it just happened, I would expect you have some dirt in the idle passages. If it has been that way since rebuild, they never set the idle mixture correctly.

 

[j_martin]

Re: 83 merc 150hp bog down

Been there, done that. 88 150 XR4 on a bass boat. Bought it with the problem.

I found.
Warped valves in the fuel pump.
rebuilt
Fuel pump pulse hose was soft.
replaced
Carbs set sloppily. (probably not significant)
rebuilt and carefully set up.
Chit in the fuel that repeatedly plugged the fuel filter.
Cleaned fuel system and installed Racor filter/water seperator
Discarded stock fuel filter.
Primer bulb and hose aftermarket substandard
Installed OEM parts
And the one that took the last little bit of hesitation out
Aftermarket plastic bayonet fuel connector
Bypassed, ran hose directly to fuel/oil mixer.

Most of this was found by installing a fuel pressure gauge between the fuel filter and the carbs. Pressure would run up to 7 lbs running, and fade out to 0 when the problem occurred. Anything over 2 and below 7 is fine.

Starving at WOT is probably the most common initial failure causing melt down of pistons. Get it fixed or you will be unhappy.

hope it helps
John