What size propeller?

[Ammonite]

Chaktoura is a 28 ft x 9ft long keel yacht. She displaces 4500kg and was fitted with a 10hp Fairyman but this was replaced in the late 90's with a 20hp Beta. In theory this should be plenty but she seems very slow (given any headwind she struggles to hit 4 knots) What size propeller would you expect for this combination and how do I go about measuring the existing prop. I'm pretty sure its the original and she spins up to max revs in gear with ease so I think its the prop that's at fault. Any suggestions?

 

[apcheval]

I am just having a prop sized for my boat. I have a Volvo engine and have been given a questionaire from Volvo to complete so that they can provide the correct prop for the boat. I suggest that you contact Beta so that they can provide you with the correct prop once you have given them the required info.

 

[cliff]

You are under-propped by the sound of it - Try this Prop size calculator to give you an indication of what you need, then phone Beta Marine and see what they say. /forums/images/graemlins/grin.gif

Or .... invest in one of these and you can fine tune the prop yourself... /forums/images/graemlins/ooo.gif
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"Artificial intelligence is no match for natural stupidity"
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[Ammonite]

Thanks for the help guys.....I'll give Beta a shout. The prop calc suggests the prop is undersized

 

[bobmay]

Fax, phone or email to www.lancingmarine.com giving: hull form, total laden weight, waterline length, horse power, RPM, and gear ratio.