Prop Questions for Displacement Timber Cruiser

[romford]

Hi All,

I am guessing my questions have been asked before so apologies for that. I have a 26 foot Halvorsen timber cruiser (a classic displacement cruiser in these parts).

As part of the re-engining process we indend to put on a new prop. I am getting conflicting information about two things.

1. The current prop is a three blade and I would like advice on the benefits or otherwise of replacing it with a four blade prop. I realise it will cost more but if there are advantages I'm prepared to do it. Any thought please?

2. We have the capacity/space to make the prop a little larger than its current 11". Are there benefits to doing this or should we stay the same size?

Any advice greatly appreciated.
Mike

[David M]

This book will answer your questions.
Amazon.com: The Propeller Handbook: The Complete Reference for Choosing, Installing, and Understanding Boat Propellers (9780071381765): Dave Gerr: Books

The advantage of more blades is smoothness. If your propeller is sized correctly, increasing the diameter of a three blade will require reducing the pitch of a new three blade.