You might check out some aftermarket performance shops for marine
applications and see if you can find a cam that will give you the most
torque and hp at the 3000 rpm mark. I am sure someone makes a cam that is
designed for this purpose.

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

Hi Guys,

Thanks for all your helpful comments. I see I'm not the only one who's
goat this brain cruncher to worry about.

As Tony suggested, I would luv to go with twin diesels, but the only
units I know of which can be mated to a Sterndrive are the Marine
Diesel V8s sold by Performance Parts Technicians (PPT). Not only would
their high torque require switching to expensive Bravo drives, but they
list for $15K. Not new enough for there to be rebuilds on the market
either.

So I'm still looking hard, and I mean HARD, at replacement gas engines.
It seems smarter to swap the 5.0 Mercruiser 200HP engines for rebuilt
5.7 Mercruisers to get extra torque, running at cruising speed with far
less throttle.

However, I read a post in another forum from a fellow who swapped his
5.7L for a 5.7 MPI unit and lost performance plus got worse gas
mileage. This was apparently due to the higher torque curve in the high
horsepower engine. Max torque was only reached at 5000rmp in the 300HP
engine, while the old carb engine reached its own Max torque at far
lower rpms, giving a bigger kick thanks to its far better midrange
torque.

I guess what I'll have to do is find the torque curves for each variant
of the Mercruiser 5.7 sterndrive I/O engines, and pick the one which
has the best low to midrange torque, forgetting what become useless
considerations of dual carb, four barrel carb, throttle body or
multiport injection.

Thanks for advice on what you'd do. Horsepower upgrades just aren't
going to cut the mustard, and plopping in 454 Crusaders probably won't
help the gallons per hour much in a relatively light 10,000 lb. planing
hull cruiser.

So it's back to the drawing board now...

Rich