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Old 07-10-2014, 12:02 PM
Bushwacker Bushwacker is offline
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Join Date: Feb 2007
Location: N. Palm Beach, Fl.
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Originally Posted by Trayder View Post
. . . Anyhow, does anyone currently run a 23 with a 225 etec? The numbers i saw were not fantastic we saw 1.9-2.2mpg BUT this was in some serious seas and pretty loaded. I am curious what pitch and # blade props others are using with the eTec
Not sure what prop/WOT rpm you're running now, but your WOT rpm should be 5500-5600, which is the OPTIMUM rpm for that motor. http://www.etecownersgroup.com/post/...post1269398114
I'd make sure engine height is correct, as many dealers mount them too low (should be able to see top of AV plate above green water when up and plane and motor is trimmed out as far as you can go without ventilation or porpoising.)

I've read articles by Nigel Calder where he's overlaid propellor power (HP vs rpm) curves on engine HP vs rpm maps. The engine power maps show islands or contours of constant BSFC (Brake Specific Fuel Consumption, (fuel flow/HP)), which is a good measure of engine efficiency. The best efficiency usually occurs near the speed of maximum torque, quite a bit lower than the speed of max HP. Calder's studies show that if you install a large enough prop to load the engine to operate at maximum efficiency at cruise, the engine won't have enough power to spin that prop up to the engines peak HP! In other words, you can get better MPG if the engine is over-propped, but that's not good for the engine, plus it will really struggle to get on plane! With a fixed pitch prop, you'll get the best all around performance if you prop to reach the optimum or max HP rpm at WOT.

In the ideal world, a variable pitch prop would allow you to load the engine for max efficiency at cruise but also unload it enough to spin up to its max HP for WOT speed. Calder is investigating hybrid diesel/electric systems where an electric motor drives a fixed pitch prop. The load of the electric motor can be adjusted to act like a variable pitch prop, so a diesel electric system shows significant efficiency advantages over a conventional direct drive powertrain, but the added weight makes it only practical for displacement or semi-displacement hulls.

One thing that might surprise your dad is to compare that E-TEC's MPG to the sailboat under power at 5 mph - I would expect it to show at least 5-6 MPG. My 150 burns 0.5 mpg at 5 mph and about 900 rpm!
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