Propeller size

[Woody1960]

Hello,

I have a Wooden Correct Craft from 1960 in very good condition. It has a PCM 351 from a Nautique 1988 with only 215hrs. After some initial adjustments the engine now runs very strong.

Engine is RH rotation & propeller also RH, and 1988. So it should be the 1:1 gearbox if my research is ok. .

The propeller has stamp 12RH14 (The 12RH is well stamped but the number 14 is not well stamped but looks like 14). The clearance between the propeller, and hull is about 1" So a 12.5" would fit a 13" dia would end up close (1/2") to the hull.

Runs 33MPH at 3000 rpm with 750lbs of people. When I use a propeller calculator I get those values (12RH14) when I add 17% slip. The 1960 Correct Craft Hull is 3/8 wood with double bottom, seems very light, it is also a bit narrower than a 2001 hull. Seems it moves easier than fiberglass hull. I will use the boat fro some skiing with light skiers, and cruising. I do not need to pull 2-3 skiers.


It seems like the propeller has too little pitch. It responds really quickly at the throttle I cannot even run full throttle without over revving. it feels it could take more pitch. What about adding 2". 12RH16 ? or 12RH15.5

Any recommendations?

[jpwhit]

Call either Eric at OJ props or call Acme and give them this same info. They are very knowledgable about answering these kinds of prop questions. And both companies are small enough to be very willing to answer such questions. Especially if you go ahead and order a prop from them. Both offer very competitive prices via direct sales in my experience if you ask nicely.

[functionoverfashion]

Agreed, Acme or OJ will help you get this dialed. Keep in mind, going from an older prop to a newer CNC one, you could have the same specs (as the old prop) but the newer prop will get a lot more "bite" simply due to increased surface area and probably better precision too. On an old boat of mine I went from an old 14x16 to a newer 12.5x15 and they were comparable.

[Woody1960]

Would a 12RH15.5 be ok with a PCM351 1:1 in a light hull?

[functionoverfashion]

Just a gut feeling, seems like a CNC 12 x 15.5 is in the ballpark. Sometimes you just have to try one and get WOT RPM with your normal load just for good data. Like I said, modern CNC props are so different from old ones. But once you have data from a newer one, you can easily step up / down. Sometimes you can try one and exchange it, not sure if Delta or Nettles props would be open to that, but I know some places allow it.