What should. Max revs be

Roberto

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Depends upon the propeller, put a big enough propeller and the engine would stop as it is engaged :)
Or any regular propeller power curve would move up and down following the fouling, sea state, etc so max RPM might vary by hundreds.
 

Tranona

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Rated 9hp at 3200. with the correct propeller you should be able to achieve a minimum of 3000rpm with a clean hull in flat water. With so little hp to play with it is important to fit a propeller that allows you to achieve the highest possible rpm
 

KREW2

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Correct. In my experience, with a dirty hull, full revs are not achievable. A lot like an overloaded car.
To the OP are you able to reach hull speed of the boat with the maximum revs obtainable If so then it would appear you are over propped, if not then fouling is likely the problem.
Due to other commitments Sunset had very little use this winter, spent a lot of time sitting in the brackish water of Weymouth Marina. When Five weeks ago I drove her over to the boat yard for the annual scrub and antifoul. The maximum revs I could get were 1800 and a top speed of 6.7 knots, far short of the 3,600rpm and 22knots top speed. No barnacles on the hull just slime, but the props were covered in tube worm.
 
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