Propeller and gearbox for a 37

Hey again guys,

So we have decided to buy the Yanmar engine finally. We will get the 3ym30. Now I feel it may be wise to look at a new propeller which is far from my area of expertise.

The decisions I would love some advice with are about the gearbox ratio to order with the engine and the propeller itself.

The 3ym30 comes with the option of 2.21, 2.62 and 3.22 ratios. Most of the websites calculators for propeller say we will need a 16x 13 2 blade prop which wont fit I don't think. Currently the boat has a 14.5inch prop and I don't think any bigger will fit. Is there any options with regard to different gear ratios and 2 vs 3 blade props that can work better?

I have read some of Lars previous comments and advice for other people which was very helpful but still feel a bit confused.

Appreciate any help!
Thanks

Fletch

Dear Fletch
Originally the Swan 37 had 15" propeller, and it is assumed this size will fit. Reduction ratio 2.21:1 recommended, and 3 blades are needed if you want to use this engine power.
As you can see in the answer to Tom it would be preferable to use bigger diameter and lower shaft rpm, but this requires rebuilding work.
Kind regards
Lars