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Posted by Jim R (141.151.78.216) on 21:21:58 22/10/05
In Reply to: Fuel efficiency posted by Skip Henderson
Skip,
I've a 1984 36' aft cabin, and can share my experience...
Almost always, the absolutely lowest fuel burn is at hull speeds (6-8 knots). I get up to 1.75 miles per gallon at 6 knots. Up on plane, there is usually a "sweet spot", but often not where you think it will be. My boat will stay on plane at 16-17 MPH at about 2700 RPM (Crusader 454's - 330 HP each with 4bbl Rochesters). From there up to about 3250 RPM, the fuel consumption is essentially flat at about .60 miles per gallon basis (higher in absolute terms, but faster, too). Above that point, the secondaries are open and the fuel mileage goes south quickly.
On running on one engine, that likely depends on the transmissions you have. You should never run at more than hull speed as it stresses the operating engine/driveline too much... My old BW velvet drive instructions state running at slow speed (6-8 knots)on one engine is OK to have a prop free wheeling. Some transmissions can get hot in free wheeling mode and should be locked down (shaft not turning), such as one engine operation, being towed, etc. Check your documentation of the transmission manufacturer's website for more info.
Hang onto the Uniflite and buy a small runabout or other vehicle for daily commuting.
: I delighted in commuting to work at Angel Island till gas prices and my wife told me it c ost too much. I have a 1972 27 foot Express cruiser with twin Crusader 220's [305 hp, I believe]. I run at 2000 to 2500 rpm depending on sea conditions for 12 to 16 mph. Am I better off getting on a plane? or just plowing slow and easy? Would using one engine make any sense? Does anyone in the San Francisco area want a great Uniflite in exchange for a fuel friendly vessel?
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