Quote:
Originally Posted by infanterene
I tried a new prop today. 4 blade 15 pitch. Top speed 40knots at 5500rpm. Cruising at 30knots I was burning 8 gpr. With the 4 blade the boat seems to ride smoother and dryer.
I don't understand why other members are hitting 50 mph with their etec 150's. The boat actually burned less fuel and was faster when it was over propped.
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Sounds like that prop is a good match if you were running with a normal load. What brand and diameter prop are you running? I'll bet you can also hang on plane at lower speed with that 4B prop!
I had the same experience, getting about 5 mpg and running almost 50 mph with my 14.125 x 20P Michigan Apollo with a light load, but it's way too much prop for the load I usually carry. I read a technical article today about displacement hulls also getting better mileage when they're overpropped. The reason is that engines are generally more efficient when they're heavily loaded running lower rpm, but you'll pay for it in reduced durability, with more carbon build-up on 2-strokes and shorter exhaust valve life on 4-strokes. Given the price on new motors these days, I've opted to trade a little performance for more durability!
07-19-2013, 10:54 PM
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