Felt like prop hub spun but think it might be a different problem (Alpha Drive)

[AS19-1]

Alpha one gen 2 outdrive. Yesterday I was out fishing and when I accelerated past 2800 rpm in to 3 foot seas the engine seemed to rev or over rev. It sounded as if the prop spun but I think it may be something else. Engine would hold 2800 rpm. Trolled the rest of the day and then was able to cruise home at 3200 rpm my normal cruise rpm. This happened to me on two other occasions but those two times I slowed down for a minute and then accelerated with no issues. I thought once prop was spun it was done. I removed the prop today it has the square style torque hub with the metal insert. ? Can you tell if that style hub is spun? Is there anything else that could cause similar symptoms. This is my first I/0
1975 Formula 233 CC
5.7 315 HP

 

[ziggy]

Re: Felt like prop hub spun but think it might be a different problem (Alpha Drive)

if ya wanna see if it's spun. paint a line on the hub and the prop. go boating. when yer done, if the lines still line up. yer good. if they don't she's spinning.

fwiw. 3' seas. maybe you were just ventilating. where the prop caught some air. it'll over rev. then... just food for thought. i know i've caught some rpms once or twice due to coming out of the water...

 

[Bondo]

Re: Felt like prop hub spun but think it might be a different problem (Alpha Drive)

if ya wanna see if it's spun. paint a line on the hub and the prop. go boating. when yer done, if the lines still line up. yer good. if they don't she's spinning.

fwiw. 3' seas. maybe you were just ventilating. where the prop caught some air. it'll over rev. then... just food for thought. i know i've caught some rpms once or twice due to coming out of the water...

Ayuh,.... That's what I'm thinkin'....

 

[AS19-1]

Re: Felt like prop hub spun but think it might be a different problem (Alpha Drive)

Thanks for the replies. I thought about it cavitating but I am pretty certain it didn't cavitate. The old formula has a really good ride with 24* deadrise. Remember this is my first I/O do they cavitate easier than an outboard? Going fishing tomorrow with a spare prop to test if it was the hub.
Started reading about bad couplers. Do my symptoms match that of a bad coupler I hope not. Any way to check coupler for failure?

 

[Bt Doctur]

Re: Felt like prop hub spun but think it might be a different problem (Alpha Drive)

Coupler failure is no fwd motion, Flo-Tork hubs simply break , no rubber insert to spin.
3 ft seas, i`m betting cavitation. Take a look to see is the diffuser is missing from the prop. Used on aluminum props only, sort of a flared ring.

 

[Brentathon]

Re: Felt like prop hub spun but think it might be a different problem (Alpha Drive)

It's not "cavitation", it's "ventilation", when air enters the blade area. Cavitation is in effect, boiling water at ambient temps due to severe localized pressure drops.
When my props spun the hub (14.5 D X 17 P Michigan Wheels), they would then spin again (very easily) at any rpm's over approx 1200. And I think the more you spin them, the worse they get (spin at lower and lower rpm's).