Something's not right. Was the bottom clean? The next thing I'd check is
the size of the props against the original equipment and find out what RPMs
they spec'd at WOT. It's hard to believe a hull could be that inefficient
but it's certainly possible.

You're right about the rpms and secondaries. Normally they open about 3400
rpm and when they do, most fuel consumption curves start to hockey stick.

jps


"Steve Helling" wrote in message
...
I recently did a sea trial on a boat I'm thinking about buying, a 1990
Thompson 288 Adventurer flybridge cruiser with twin 350 mercruiser
inboards.
I was disappointed to find that at 3200 RPM, trimmed for max speed, it
could
only make 13-14 knots, as indicated by GPS, and at WOT, around 4800 rpm,
it
topped out at about 24. This was in glass-smooth protected waters with
little wind. The engines seemed to be running fine, but this seems a
rather
slow boat. It's my understanding that much over 3200 rpm the 4bbl carbs
open up and send fuel consumption through the roof. Any thoughts or
advice
for this beginner?

Steve