New prop for my 390

May 17, 2004
5,026
Beneteau Oceanis 37 Havre de Grace
Measure the max in neutral as well to make sure the engine is capable of getting to 3000.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Do you think that max rpm in idle and in gear should be the same? What about the drag of the prop? It has to effect the rpm in gear.
The drag of the prop will make the boat go slower, wasting RPM/engine power. If the engine is running properly, whatever RPM you get in neutral WOT, you should be able to get WOT in gear on the water- NOT tied up at the dock.
 
Feb 27, 2018
1
Beneteau Oceanis 390 King Harbor
It was measured when the engine is in gear.
The rpm was measured on the crank shaft which is the correct engine rpm. It was 2522. the tachometer showed 3550 but I guess it is faulty and need adjustment.
I don't think I have excess rpm. I think its the other way around.
Graphs provided by the manufacturer show that the max rpm should be 3000 and the gear ratio should be 2.14.
Yorammelnik, I'm doing about the same thing, same boat, same engine. I'm wondering what year your hull is because I'm trying to work out if I have the same gear ratio. Hopefully you still check these forums.
 
Sep 21, 2014
12
Beneteau 400 White lake
I have a 95 OC 400 with a Perkins M50 also. We purchased her 4 years ago, and had an Autostream 17" stainless feathering prop already installed. Easy to adjust for forward or reverse pitch, grease and change the zinc. It is pricey($3200) but still looks new.