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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 2001 Mirastar 23' boat with a fuel injected 330 hP

Customer Question

I have a 2001 Mirastar 23' boat with a fuel injected 330 hP engine its running a 20 pitch prop at sea level I am now around 4500- 5000 feet what should I be running prop size
Submitted: 2 years ago.
Category: Boat
Expert:  Ted G. replied 2 years ago.
Have you actually tried to run it at that altitude? A modern fuel injected engine may not lose that much power at the change of altitude, so your prop on it now may be fine. Or if you have run it, what is the maximum RPM it will run with a normal load?
Customer: replied 2 years ago.
It runs out with the 20 at 3900 RPM
Customer: replied 2 years ago.
with the 118 pitch I could only get around 3700 HP at sea level with the 20 we were around 4500 RPM
Expert:  Ted G. replied 2 years ago.
Then there is something wrong with the 18 or it is mismarked, it should at least turn more RPMS than a similar 20. And if the 20 is turning 3900 then an 18 is exactly the right number to bring the RPMs back up, figure 300 per inch of pitch.

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