How does one determine prop pitch?

[NickScheuer]

Can it be done with the boat on her trailer? Are the specs stamped into the prop somewhere?
The Albin-25 Handbook specifies 16-1/2 X 12", however, there are a lot of engine/prop combinations in use out there so I wouldn't want "just any old prop" from another Albin. The DuNORD has her original V-P MD17-C. The idea of getting a spare prop before the one in use is damaged appeals. We had a spare for the outboard on our former sailing yawl and switched props on cruises twice over 18 years..

[WillieC]

I gave all my hull and engine specs to two local prop shops and both came back with 17" diameter X 13" pitch. The WillieC is Gen 2, Deluxe, with the MD17C. Per Brohall calls out 17X14 in the original manual with the MD3B engine, virtually the same engine.

So I ordered a 17X13. I suspect 17X14 would work just as well since I do not intend to go to full revs ever in this 45 year old engine. Likely not much more than 75-80%, 2000rpm.

Is the 16-1/2" X12" the spec for the AD21? Mr. Kirsop?

[dkirsop]

The 16-1/2” x 12” is for the AD21 engine. The 3 cylinder Volvo’s have the power to swing a larger diameter prop. Having said that I found that I achieved better speed and economy trimming my prop to 16” and cupping the blades. Prop sizing is an approximation that requires sea trial to fine tune to the boat and engine. Richard’s advice is probably spot on for your type of engine.

[NickScheuer]

Actually measured our prop yesterday and discovered it to have an 8.5" radius, which of course works out to 17" dia. (can't measure dia across 3 blades). Dis not take time to hunt around the hub for stamped data disclosing pitch.

[NickScheuer]

Found the hub stamping. Had to use emery paper to rub off caked paint, but "17 X 14" was revealed. Have noted my Owners Manual. Thanks, dkirsop.