prop mistery

[hugues1811]

I just bought a endeavour 40, i am new in the sailing comunity.
when i tried the boat, the engine reach only 1800 RPM( really slow) and the boat was doing 6 knots (not too bad). it looks like there is too much pitch on the prop, this is confirm by 2 different prop manufacturer, they advise to install a 16x10. The engine is a perkins 4.108 rated at 50hp at 3600rpm and it is the original engine, the transmission is original and have a ratio off 1.87, the prop is a 17x16rh and this is what recomended endeavour. who is wrong , and which prop i need to install. anybody have a similar size engine/boat and can tell me wich prop to use ????

 

[Steve Dion]

Hugues: Contact these guys. If you want a fixed prop, there is nothing better than a Campbell Sailor. They also sell a few others if you have a "boatload" of money.

http://www.westbynorth.com/

Their specs will NOT match what you would get with a standard 2 or 3 bladed prop., so you cannot go by that.

 

[Mike Holibar]

The 4108 is a good solid old engine and can take a bit of overloading. However if you had a similar over propping situation with a modern diesel you would probably void your warranty. I have a perkins m50, 50 hp@ 3000, 2:1, and the prop was 18 dia by either 13 or 15 pitch - the three or five is partly obscured. At this she was slightly over pitched, 2900 rpm max. Given that my shaft will be rotating slower than yours it would appear that the prop guys are nearer the mark. If you get the pitch right so you can develop full rpm, there are a couple of benefits. Firstly you will get the full 50 hp. As it is running just now you would be lucky if the engine can develop even 25 hp. Secondly your fuel consumption will drop dramatically. On my boat I changed to a 18 inch Kiwiprop, a feathering type, and adjusted the pitch to allow full rpm (and therefore full power) to be developed. It is a common thing over here to over pitch props mainly because people dont understand the rules regarding engine performance and propeller power absorption. My last two boats were over pitched and, while not a problem in light conditions, the lack of power and excessive fuel consumption were very apparent in heavier head winds and seas. Getting the pitch right resulted in a dramatic improvement in performance in both boats. Cheers,

 

[higgs]

If you got money, the Maxi Prop, whose pitch can be adjusted and is a feathering prop, is a really good prop. For your boat, though, you are looking at 3k.