Join Date: Feb 2010
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Ask the company that recommended a 14x9 prop what they will charge you to re-pitch the prop if you find it necessary. If you can't hit hull speed using their recommendation they may re-pitch it for a nominal fee (I doubt that they'll do it for free, but who knows). I would be careful not to over-pitch the prop.
It's often stated that you should be able to hit hull speed at about 85-90% of the engine's max continuous rpm rating, which a quick Google search indicates is 2600 rpm for (rather than 3800 rpm) for a 2QM20H. I suspect that a 2QM20H may be pretty close to the lower limit of engine size for a 13000# boat. Ted Brewer recommends 3 to 4 b.h.p. per ton, which in the case of you boat would would be just about right. However, Brewer doesn't seem to consider it necessary for an auxiliary sailboat to maintain hull speed under power. And, there's nothing magical about hull speed anyway; 6 kts is probably plenty fast.
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