Propellor sizes

[Guest]

Is there a formula/rule of thumb/guess/law etc on how to work out what sort and size of prop to use with any particular motor?
I'm just about to put a Volvo 18HP diesel into my yacht [ to replace a Stuart Turner 10HP] and have no idea what sort of prop I should be using.
Props are expensive, so trial and error seems a little impractical.

 

[Gaffer]

There is a formula for working this out based on the HP of your engine and the RPM, but I havn't a clue what it is..........phone any propeller manufacturer and they will recommend the correct size and pitch for your requirements.

 

[oldsaltoz]

G'Day alibaba.
Have a look at the link below, it may have some answers for you.

http://www.deltaprop.com/linksi.htm

Avagoodweekend Old Salt Oz......

 

[dickhicks]

Most propellor manufacturers get you to fill in a form from which they can calculate the correct size for you. Try CJR, they are good and helpful.

 

[seahorse]

The "Westerly Owner's" site used to have a programme to download which I found to be pretty accurate when I changed my engine & fitted a folding prop.

 

[Jcorstorphine]

Please note that the link on the Westerly Owners site to the prop calculator does not connect. Surfbaud appear to have reorganised their website. If you log on to www.surfbaud.co.uk you will find an instruction using one of their links to an address where the program can be downloaded. If you have problems, send me a msg and I will e mail you a copy. It is pretty good and takes into account all of the variables such as length, weight estimated speed etc.

John C.