Help finding a Propeller

[col50]

Originally Posted by Uncle Bob

My go to would be get a suitable new prop, disconnect the coupling at the gearbox and slide the shaft back sufficiently and have a spacer made to extend the shaft, coupling to gearbox. If insufficient space then a longer shaft, positioning the new prop at the required position.

Good idea Uncle Bob.

[jmastal70]

Welcome, and if you don't find anything near Jersey shore, give New England Prop a call in Plymouth, Ma. 8006359504. He's the largest shop in New England and by the looks of his shop, he can probably make whatever you want { or not}. Good luck.

[GrowleyMonster]

Originally Posted by ItDepends

Matt,

Isn't it frustrating when you post the right answer, and nobody seems to read it, but they continue to run off with craziness?

Back to the OP, you have a problem here. The maximum distance from the forward face of the prop to the aft face of the cutlass bearing is 1.5 times the shaft diameter. So despite the postings here NO you can't just make the shaft longer! You're best bet is to consult with a propeller expert, and have him review the clearances and dimensions. There will be no perfect solution, but I can assure you so far none of the advice posted here so far is close to the best you can do.

That is EXACTLY what I would do. That extendo-whatever plastic prop is waaaaay aft of the cutless bearing. So? Not a total deal breaker. I would get a longer shaft, cut it so that a reasonable diameter prop would still have good hull clearance, install that, and a prop. Going with a four blade prop would increase drag, (assuming fixed prop) but not by much, if while not under power the prop is kept with two blades lined up vertically. That makes two blades out there catching water, same as a three blade prop. Four blades would allow a smaller diameter to load the engine properly. A slight increase in pitch, while not ideal, would maybe be acceptable under the circumstances. Going maybe 10" x 10" would only require a modest increase in shaft length. A mitigation of the higher pitch is that higher pitch equals less drag.

The better solution would be a new, relocated strut, new shaft, and new prop. This might be prohibitively costly, though.

If I understand correctly, the original prop was smaller because it was turned by an A4 with a 1:1 gear ratio. If a gear set for the transmission is available with a lower reduction ratio, that would help a bit in making this all work together. With a smaller prop, tip speed is reduced and so a somewhat higher prop RPM can be tolerated.

Your advice to consult an expert is sound, though. I certainly can't find any fault with that.