I am thinking about a new prop to improve mototing speed, but would like to hear from some 365 owners who have some knowledge or experience to help with this decision.
My 1979 Pearson 365 was repowered by the previous owner with a Perking 4.108, rated at 55hp at 4,000 RPM. I believe the original Westerbeke w40 was rated at 37hp at 3,000 rpm, so the repowering resulted in increased power. I'm not sure about the transmission, but the V-drive appears original. The current three-blade prop (17" x 10") may also be the original. It drives the boat at approximately 5 kt at 2,300 RPM, which seems slow to me. I have been led to believe that the Perkins 4.108 should give me at least 7 kt with a modern prop of the proper size. Is this reasonable to expect? If so, does anybody have any recomendations about prop maker, prop size, pitch, etc? My current thinking is toward a fixed three-blade prop, but I am curious about folding or feathering props.
You need to identify the vee drive and see if it is original. If it is, you may run into a torque problem if you upsize the prop. I don't remember the numbers, but 55 hp at 4,000 rpm sounds like it may be over the top of the vee drive rating.
If you stay with the current prop, you may be OK because the prop will only absorb so much torque, limiting the load on the vee drive. Try to identify the vee drive and see what you have. You may need to change it in order to be able to reprop and use the additional horsepower.
The V-drive is the original one by Walter. I never run the engine at 4,000 RPM, so maximum HP is just theoretical. According to the manual, it develops 83 lbf ft at 2200 RPM, which is very close to my usual cruising speed.
My impression is that a modern prop of the same size (and even without a more powerful engine) should give greater speed than the prop that came on the boat thirty years ago. Has anybody upgraded props, and if so, can you share your experiences?
i used to do 6 knot at 2200rpm with original 17x10 prop.
5 knots may mean gearbox is slipping or there is a good headwind or current.
55hp is a bit overkill for the 365.
dirty prop and dirty bottom will slow you down seriously as well.
Mike,I run a perkins 4-108 a Borg Tannie Walter drive and a 17 inch 3 blade prop I will have to check the pitch on the prop.My cruising speed is 6.5 knots at 1850 rpm very smooth and burnes .66 gal.per hour. Allen
Mike,
Sea Dragon has 3 blade 18x11 prop attached to a Westerbeke W40, Paragon, and a Walter V-drive. At 2,000 RPM she makes about 5.5 knots and burns just over 0.5 gallons per hour.
Garner
My numbers are almost identical to Allen on Incommunicado. (W40 4-108, Borg Warner Velvet Drive, and Walter V-drive).
I've been thinking of replacing my prop with a feathering prop and ran across the Kiwiprop (http://www.kiwiprops.co.nz/). The price is right and you don't need to install a shaft brake (for those of us with hydraulic transmissions).
Dirk
With the origional transmission and Vee Drive the prop should be 17 inch diameter 3 blade 12 inch pitch. This should give you 6 knots at 2000 RPM. This works with several boats that I have worked on.
I doubt that the new 4.108 actually produces 55 hp in real life. That rating is based on 4000 RPM which none of us run. About 40 HP is correct.
Some boats were equiped with 2 blade 18 inch diameter. Has anybody ever run a 18 inch 3 blade prop? I dont see why this would not work but I dont know what pitch it would be changed.
I am a little confused. Some people indicate they get 5.5 kph, others 6.00 kph and still others 6.5 kph. Also, the prop on my boat is a 17" x 10", while one reply indicated the size should be 17" x 12". Is it possible that Pearson changed the prop size at some point during the production run? ???
After I cleaned my original prop and finally made the proper adjustments to my borg-warner transmission (three tries), my speed increased from under 5 kts to over 6 kts and reverse works much better. Concentrate on the transmission first.