propellers

[davedoel]

anyone know which pbo edition contains the formula for calculating the correct size of propeller ?

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[philip_stevens]

Download "Surfprop" from here <A target="_blank" HREF=http://www.surfbaud.co.uk/download.php?list.7>http://www.surfbaud.co.uk/download.php?list.7</A>

<hr width=100% size=1>regards,
Philip

 

[staugur]

I'm an expat living in florida and I've just totally rebuilt an "87 wellcraft 27' nova and upgraded the engines from two 260's to 325's bhp's and the biggest problem I'm having apart from finding the greenbacks is the props!.I've researched this to the point I may be the worlds expert. NO ONE CAN TELL WHAT IS THE BEST PROP FOR YOUR BOAT> do I need to do that again? All you can do is take an educated guess,stick it or them on and go run the boat. You should know the engine manufacturers recommended working rpm's for the engine and assuming every thing else is perfect if you can't reach that then you are overpropped and nead to reduce the pitch,if you can then increase it.It can get real expensive if you can't find a prop shop that will help you out with demo props.Do your best and perservere.The way it can alter speed and economy is mind boggling but unfortunately theres just not enough interest out there for the common boater.Now if you go offshore racing!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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[Evadne]

Is that why self-pitching props were invented, or are they biased so they give a certain pitch for a given rpm, and thus just as difficult to spec.?

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[oldharry]

Self pitchng props are pretty much as difficult as the fixed variety, and still have to be matched to the engine. Their advantage is that when the engine is having to work harder into bad conditons, the prop will 'flatten' and allow the engine to continue to develop plenty of power while a fixed prop will slow the engine down killing power output. However the 'full open' posiiton must match the engine for normal conditions, in order to work properly when its bad.

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