Fuel starvation or bad coil or bad distributor.
Get a fuel pressure guage and install (cost about $15 to $20 at any
performance auto parts store). This is a good thing to have anyway for
future problems.

If fuel pressure is good when if sputters then I would start w/ the coil.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
wrote in message
...
I have a 1993, 25 ft. Searay. It's got a 7.4 Mercruiser Bravo (454
Chevy). It runs great untill I hit about 3000 rpm, 3/4 throttle, then
it hesitates, and sputters. I've replaced the 4 barrel carb,
sparkplugs, wires, fuel filter, and put in fresh gas. No improvement.
It seems to run good when running on two barrels, but when the other 2
kick in, the motor chokes. The local boat mechanic hasn't got a clue,
so any help appreciated.