We have a 31' LOD, 25' LWL full keel sailboat. The beam is 10' and she has a 5' draft weighing about 16K-17K. She is a wine glass as they call it.
We are looking into BetaMarine engines and would like suggestions. We thought the 28hp would be acceptable but would like input prior to a final decision. Oh, the prop that came with it is 12" dia and a 13" would possible work but no larger. We are open to suggestions?
Hello, The limiting factor on your repower is the restriction in prop diameter. Basically on a full keeled boat you are better off with a larger, slower turning propeller whereas on a fin keel boat, the faster prop works fine. You will have to live with a bit of prop wash noise when you push the engine to high speed. You should be quiet up to 5.5 or 6 knots.
Using the Beta 25 with a 2:1 transmission you will want a 12"x9" three blade (or 13"x8") and 1" extra pitch using the Beta 28. The larger prop will be a bit better but if you dont have at least 10% of prop diameter as tip clearance (15% is better), you will have excessive prop wash noise. That said, the props that I have listed above are efficient and have good blade loading which translates to good fuel economy and smooth power delivery.
There is very little difference in boat performance between the 25 and 28HP engines. The choice may be dictated by the space in your engine room and your requirements for large alternators.
Please let me know what engine (and transmission) you are replacing and what are your electrical requirements.
It has a Bukh in it currently. Our existing prop is a 3 blade 12x8 LH. We were trying to maintain the 15%, so a 13" prop will be fine. Electronics are really minimal as this is just used as a weekend boat and not a cruiser.
Hi, I would use the the Beta 25 in your boat. This engine has much more power than the Bukh DV20 ever had so there will be a very useful improvement in performance. You will be going to a RH propeller for the new engine.
The prop calc comes up with 13"x10" three blade and this will provide good boat speed and economical and quiet cruising.
