OMC 5.0 stalls under hard accelertation

[vasy]

Outdrive model is: 3868156
Engine model is: 502APHUE

Engine block has about 40 hours on it but accessories are of unknown age. Holley 2 barrel carb.
When accelerating normally, the boat goes to 4500rpm and pulls strong and runs all day long.
But when pulling up a wakeboard, if I just give it quickly from idle to full power, it stalls.
I can restart the boat quickly with out any issues but same things would happen again if I try.
If I give it like 10-15% throttle at start and wait a moment and accelerate progressively but fast (faster then normal cruising) it would pickup ok but engine sounds a little funny.Like rrrrrrrr..rrrrrrrrrr with a small pause in between for like 1/4 second.
This make pulling a boarder up a bit painful as the guy has to fight slow pull at the immediate start and a little cough as he is about 1/4 way out of the water.

 

[Scott Danforth]

sounds like your accelerator pump in the carb is failing. most likely you need a carb rebuild.

 

[vasy]

Lovely
Would you advise to rebuild the carb, purchase already rebuilt carb or upgrade to a 4 barrel?
Would the 4 barrel make a noticeable performance difference and if so, would it be at a much greater fuel penalty?
For a 4 barrel I'd also need a new intake, correct?
Thanks

 

[kenny nunez]

You can purchase the acclerator pump repair separately from PEP BOYS . Remove the carb. Flip it over and remove the 4 screws to replace the pump. If you want to go the 4 barrel route only use a dual plane manifold with the correct marine carberator . It will probably give another 20-30 horse power on the top end.

 

[vasy]

Thanks for the advise. Sounds like 4 barrel is a no need for me. I'm good with the current power output and hardly ever use top end.
I have the rebuild kit already, was waiting for the winter to come around before I dig into a carb
I might have to do it earlier then planned.

 

[vasy]

Just wanted to post an update.
Finally got around to paying with the carb. The rebuild kit I had was no a total match, so just put a new needle and seat, new bowl gasket and accelerator pump. The old one looked like it had a small crack in the diaphragm.
Also the linkage that operates the accelerator pump was gummed up with rust and crud and was not returning to the initial position.
So cleaned up and polished the linkages and new diaphragm and so far initial test are good.
The boat starts much better then before, idles better as well as accelerates without stalling.

Thanks everyone for the help!