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(Hemicuda) wrote in message . com...

You're going to fabricate water cooled exhaust to and after a pair of
turbos and you think that will be cheap and easy :-) Along with the
rest of the intake plumbing. Making a go fast boat is going to cost
you in fuel use, that is hard to avoid. And unlike cars it takes a
lot of power to make a little more speed. Just adding a blower or
turbos to your stock engine will probably kill it in pretty short
order too. You're going to want to run it at wide open throttle for
minutes at a time. This is not like a car where it is hard to keep
the throttle floored for more that a few seconds.

Just to give you an idea of what you might be in for. I went from a
stock 5.0 to a reworked 4 bolt 5.7 with all roller valve train, kb
pistons, eldebrock heads, crane cam, holley carb, and stainless marine
exhaust. Made my top end go from low 50's to mid 60's. If I make it
go any faster I'll need to go to aftermarket steering, 60's is about
all any sane person would want to do with the factory merc steering.

So from what I can summarize from the above posts are that the turbo
will probably work great while cruising and at top end but will be a
dog coming out of the hole. This is a dumb question but I thought
that at slower speeds boats require less horsepower to move them
through the water. As the speed increases so does the power
requirement for a certain hull design. Is this true? If so it
appears that the low end lack of boost shouldn't kill me. Or am I
totally of base? The other thing I was thinking of was to put smaller
turbos on the engine to reduce lag but sacrifice top end boost.
Marine engines rarely go over 5,000 RPM so I could probably go with a
smallish turbine housing with a waste gate that will bring on boost
quickly and then dump the excess exhaust gas at higher speeds. I know
the heat will be a problem but I think that is manageable but I don't
want to take forever to get up on plane. Has anyone seen or ridden in
a gasoline turbo'd boat and seen how bad the hole shot was? The
reason I want to stay away from a blower is that although it will
boost power I think it will hurt the fuel efficiency. Also blowers
tend to be expensive and I can score a pair of T3 Turbos from old T
birds which would fit a 5.0 or 5.7L fairly well for cheap at a junk
yard and fabricate a set-up. Thanks for all the help and I
appreciate any more thoughts or info you could pass on!