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Joined: 2/22/08
Posts: 3
Performance Under Power

I have an Autoprop feathering prop which gives great performance. Unfortunately the prop is overpitched at the factory setting; the engine does not reach full rpm and leaves smoke on the stern. I am going to reduce the pitch but I need a benchmark for C-36 speed under power. What is the expected or normal speed through water at crusing RPMs that should be expected? Any experience would be helpful!.

TomSoko's picture
Joined: 2/15/07
Posts: 978

Can't answer your question without more info. It would help greatly if you could update your "signature" in the forum. Need to know more info about the boat, engine, etc. Is your engine a 21 HP M25, or a 35 HP M35, or somewhere between? I also have an autoprop, and I went back and forth with Steve at AB Marine when I first bought it. He insisted that the pitch and size of the autoprop were proper and according to specs, but I insisted it was too much. Anyway, my prop went back to "the factory" to be re-pitched. It helped somewhat, but I feel they could have reduced the pitch even more than they did. Your diameter should be NO MORE than 15", even if AB Marine says "It's close". The transmission reduction ratio is 1.79:1 for all tranny models. Feel free to contact me directly. I'd be happy to chat with you offline.

gforaker's picture
Joined: 7/20/07
Posts: 133

I think it is just the nature of the beast to not reach full RPM under load. With my MKII I get to maybe 150 or 200 RPM of maximum under full throttle, but don't consider that a problem. I don't see any black smoke out of the back but there is a little residue on the stern. I see the same residue on all of the other boats in the marina.

Gene Foraker

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