Man, do I need help. Have a 99 Four Winns Horizon 190 with Volvo Penta 5.0 I/O. Suddenly, it was fuel starved and would not run. Replaced fuel filter, then fuel pump, then had the Holly carb rebuilt. It now runs, but when you hit the throttle out of the hole, as in pulling skiers, it bogs down, but then catches and runs fine. However, even at higher RPMs once it's running, if you give it extra throttle, it hesitates before accelerating. Once it's at full throttle, it's fine. I've also had a new ignition coil, points, rotor, plugs, etc. replaced. Accelerator pump was replaced with carb. I've got the best mechanic in my area working on it, and he is completely stumped.
Antisiphon valve was replaced early on
as well as the fuel filter. Mechanic
now looking at replacing spring on
accelerator pump and/or checking
out the two jet nozzles leading from
carb. It is a 2bbl Holley on a 4bbl
manifold that is stock but he says a
bit unusual. Thinking of seeing if
the new fuel pump was bad, but
that would not explain why it runs
fine at full throttle once you can get
it there. Any other thoughts? Many
Was a solution ever identified. I have the exact same issue with my Volvo Penta. Boat mechanic blamed it on the ethanol in the fuel and was leaning towards rebuilding the carb or replacing the accelerator pump.
Things aren't always as they seem. I had a performance problem with one of my 5.0 FI engines. No power at wide open throttle. After performing a routine bellows replacement on the outdrives, I found two flapper valve plates blocking the exhaust. These are useless plastic parts and Volvo released a bulletin to remove them completely. Under WOT, they would block the exhaust forcing the gasses to exit through the small bypass hole in the bottom of the transom plate. Your boat may be new enough to not use these parts but couldn't hurt to look into it.