I think I mentioned that a cpp and pyrometer would be the best way to assure
not being overpropped, or words to that effect. I don't know any
manufacturers that intentionally overprop a boat, but then again, I am
certainly not familiar with them all. I do know that everyone that I have
talked to or read about, that intentionally overpropped there boat
(overdrive mentality ?) decided to prop it correctly later. ymmv

I own a 1985 Willard 40 with a Perkins 6.354 whose manual states that it
should be propped so that it can achieve WOT at 2800rpm. Willard equipped it
with a 28x18 three-bladed prop. Underway, max rpms was 2550 rpm on an
adjusted tach. The engine seemed to labor and the engine room was always
very hot, but the engine ran at normal temperatures, although it came up to
temperature very quickly.

I changed the pitch twice determining, finally, that 28x17 allowed 2800 rpm
and I could cruise at 2200 rpm instead of the previous1800 rpm. There is now
less noise and heat. However, top speed has dropped from 8.6 knots to 8
knots. I don't care because cruise has been 7 to 7.5 knots and I intend to
experiment at lower speeds to find the most fuel efficient compromise.

Ron Rogers

----- Original Message -----
From: "Patrick Gerety" alohaboat@yahoo.com
|
| Willard Marine was founded by Bill Tighe (now
| deceased) back in the 1950's.  Bill was a big fan of
| over-propping.  All the Willard 30's, 36's, and 40's
| produced in the 60's, 70's and 80's were over-propped.
| However diesel marine engines were a bit different
| then and evidently the makers  encouraged
| over-propping to some extent.
|
| I don't encourage over-propping with the marine
| engines that are available today.  The conventional
| wisdom and recommendation of diesel makers today is
| that the engine should achieve maximum rated RPM's at
| WOT under load.