The reason for your problem is your not turning enough rpms so you are
lugging the engine. Check the following.

1. Is compression good on the engine.
2. Is the carb clean and adjusted properly.
3. Are you getting good ignition/firing.
4. Are the correct size props installed.

You can verify the carb and ignition by looking at the plugs while out for
the compression test. If they are clean then you can probably rule out the
engine if it seems to crank and run smooth.

However based on your numbers provided, my guess is you have 18" pitch props
which are a little too big. Probably need 15" props to get the rpms back
up. This will help with acceleration and fuel economy. The numbers
indicate that the engine is ok if indeed you have 18" props.
The original owner probably damaged the original props and got a deal on a
set that was not quite the correct size. However, please verify the engine
is good before you start playing with props.

--
Tony
My boats and autos - http://t.thomas.home.mchsi.com



"Prosndinc" wrote in message
...
Anyone out there with a Chaparral 2550? I just purchased a 1995 with a old
style volvo Duo prop and a 300hp 454 engine with B4 prop set. The boat
can't
seem to get out of its own way. Lousy holeshot, only 4200 WOT @ 42mph and
terrible fuel economy. I am wondering what others with this combination
are
getting.
TIA Charlie