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welshswampy

Regular Contributor
hi, i currently run an aq 130/270 out drive on a 20ft wilson flyer cathedral hull(approx 1-1 1/2 ton) the prop is 14 x 15 pitch and even on W O T am only getting 12 knots max, could fit up to a 16 inch diameter prop if required, i am looking at a 15 x 17 pitch prop online, does anyone know if this prop would be suitable to get me more speed, or would i need something else? many thanks all
 
What are your RPMs at WOT? If you're getting about 5000 RPMs, then your current prop is matched pretty well to your boat. Basically speaking, the goal is to get a prop that allows your engine to reach it's max WOT RPMs without going too far over or below the max WOT RPMs for your engine. With that said, my boat (see avatar pic) is a 17' v-hull that weighs about 2000 lbs. with the same AQ130/270 combination and it goes about 33-34 mph at 5000 RPM on flat water. I would not expect that sort of performance out of your boat however given its weight and hull type. A 15x17 prop will provide a little more top end speed at the same RPMs as a 14x15 would, but at the expense of slower acceleration. But again, the place to start is to see where your WOT RPMs are as compared to the engine's WOT RPM specification and go from there. A 2 pitch increase in pitch will decrease your WOT RPMs by approx 400 RPM and conversely, a 2 pitch decrease will increase your WOT ROMs by approx 400 RPM.
 
thanks for reply, as for rpm at wot, the engine is nearly 40 yrs old and i wouldnt like to take it up that high(shes quite an old girl and id like to keep the engine a bit longer) but when prop arrives ill let you know how i get on, regards nick
 
Nick, I appreciate how you want to treat an old engine gently. Good luck and let us know how things go with the new prop.

Bob
 
hi, havent really fully tried out new prop,( bad weather forced us back in) but seemed to go up on plane quicker and with less revs(didnt have chance to alter trim etc due to speed restrictions)but i am hopeful, however i have the chance to buy a VP 2003 40 hp turbo diesel, does anyone know if this will fit a 270 leg, and if it will be a worthwhile exercise?
 
FYI..... WOT RPM is a test RPM ONLY...... not intended to be a sustained RPM. (see your Volvo Penta OEM manual)

You will do more damage to your engine by continued use of a propeller that does not allow WOT RPM to be achieved, than you will by NOT reving up to perform a WOT RPM test.

If a propeller were to be too "steep", you will "over-burden" your engine throughout the RPM range, eventually causing premature failure.

.
 
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