On Tue, 30 Dec 2003 04:00:50 +0000, Gould 0738 wrote:

Robert at Atomic Engine Service (where I'm buying the engine and prop)
recommends 14x8 (grudgingly 14x9).

You might consider paying some attention to this recommendation. This guy
realizes that you will be knocking on his door *first* if you're unhappy with
the final combo.

Catalina recommends 14x9 for the ORIGINAL M25 (21hp compared to 26hp for the
new one)

Also likely a well-founded recommendation. About agrees with your engine
supplier.



I think 14in is a good diameter - I'm concerned that a bigger prop means more
drag. I'm leaning towards 14x10 but...??

If the original engine was 5 HP (about 20%) less than the new one, it wouldn't
seem unreasonable that your new setup can handle an extra inch of pitch.

You can worry a thing like this to death. Most of the recommendations are pretty
close, so if you want to stay with a 14" prop the 9 vs 10-inch pitch won't make
the difference between satisfactory results and
anything dramatically less.

Ya know Chuck, you might just be right: I may be overthinking this. My concern
comes from my belief that the single most important factor in getting the most
out of your engine is pitch (followed by prop diameter).

As you say, I'd like to lean towards Robert, but he seems out of line with the
rest of the estimates. But I think I can convince him to let me go with 14x10,
mentioning that I can re-pitch in April/May when I do my "annual" scrape'n'paint
haulout. But you're right: I may not see ANY difference between 9 and 10.

Lloyd Sumpter
"Far Cove" Catalina 36