Prop for a Catalina 30? What one to use?

[romantic comedy]

A buddy asked me about his buddy that has a Catalina 30 with our favorite engine.
He wanted to know what prop he should use. Pretty simple I guess.

So, what prop would you recommend for a Catalina 30 with the Atomic Four, please? (I dont know any other info)

[ndutton]

The factory prop for an Atomic 4 direct drive in a C30 is a 12x7x1RH fixed 2 blade. On a well maintained and tuned engine he can expect around 2100 RPM max. Last year in a quest for more RPM (like running in a slightly lower gear) I switched to a 10x8x1 RH fixed 2 blade and now I max out at 2600 RPM but typically cruise around 2300.

If he's interested I may have my old 12x7 available. I say may because I loaned it to a C30 slip neighbor for a test drive a few months ago and have neither seen nor heard anything back yet. The prop is in decent shape, no dings or gouges.

[TomG]

I don't know a lot about boat propellers, but what about the Indigo prop? I know we can get into some quantum mechanics with the dark art of proper propping, but I love my little Indigo. It's allows the engine to rev higher, is quieter, and cuts way down on prop walk. It was designed specifically for the direct drive A-4.

What does you buddy think about the Indigo?

[sdemore]

There was a discussion thread last year on the Indigo prop. As I recall, it turned out to be roughly a 50/50 mix of Protestants to Catholics.

[thatch]

Like Neil, I found that the stock 12x7 on my C-30 would only allow my A4 to reach about 2000 rpm without loosing considerable manifold vacuum. Ironically, Catalina supplied the same prop on their 27 footer, which was my first clue that they may have over-propped the 30. My first change was to an Indigo, which got my engine speed up to where it should be, but I felt that it's winglets were a definite detriment to it's reverse performance. The next change was to remove 1" from the overall diameter of the 12x7, which has raised the engine speed and vacuum up to far better levels.
Tom

[romantic comedy]

Thanks guys. Will pass along the wisdom....