Loss of thrust, Rpms redline instantly
08-06-2010, 09:18 PM
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Loss of thrust, Rpms redline instantly
Was out tonight, boat was running fine, threw it down wot, and a few seconds later I lost all forward thrust and flew forward, rpms went above 6k. I have an 89 22ft scarab with a carb 350 mag, alpha gen 1. I limped in at idle, boat does fine till around 1200 rpms and then I lose thrust and the rpms skyrocket. Reverse works fine still, shifting seems normal. With boat off and in forward drive prop locks to the left and spins fine clockwise. In reverse it spins freely in either direction. Is this a tranny issue, or outdrive? My buddy who slips at my marina suggested the prop is slipping and that it is as simple as the rubber gasket or ring inside the prop needs to be replaced.....another thing I noticed, I felt some sort of different vibration as I lose thrust above 1200 rpms. I listened to the engine and the only difference I hear is something that sounds like a rattle(not very loud) near the drive, however that could have been there before so idk. Any help is appreciated
08-06-2010, 10:57 PM
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Sounds to me like you trashed the drive coupler. It couples the drive to the rear of the engine at the flywheel. Drive will have come off and engine pulled to change it. Sounds like it's more than just a spun prop hub though that would be the first thing you would want to check.
08-06-2010, 11:15 PM
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Sounds to me like you trashed the drive coupler. It couples the drive to the rear of the engine at the flywheel. Drive will have come off and engine pulled to change it. Sounds like it's more than just a spun prop hub though that would be the first thing you would want to check.
I hope that is all, I have had no problems until today, boat runs great and hard.....is a failure like this common with no symptoms?
08-07-2010, 08:14 AM
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It is very common with rubber hub props. I don't think it is the coupler, or it wouldn't move at all. I would bet it is the prop. You may not be able to tell right away. Just pull the prop and take it to a prop shop and have it replaced.
It should only be about $50.
Eddie
It should only be about $50.
Eddie
08-08-2010, 08:46 PM
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Sometimes the hub can spin without showing visible signs when you pull the prop. Depends on whether it is the old press in style or the flo-torq interchangeable kind.
One way to know for sure.
Spin that baby up for ten seconds, immediately kill the motor, dive in the water and grab the prop hub. If it's been spinning it will be hot. You'll have about fifteen seconds to check, cause the heat gets pulled off of the prop by the surrounding water pretty quickly. But if it's the hub, the prop hub will be hot.
MC
One way to know for sure.
Spin that baby up for ten seconds, immediately kill the motor, dive in the water and grab the prop hub. If it's been spinning it will be hot. You'll have about fifteen seconds to check, cause the heat gets pulled off of the prop by the surrounding water pretty quickly. But if it's the hub, the prop hub will be hot.
MC
08-10-2010, 09:47 AM
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Pulled the prop yesterday, hub appears to be shot, rubber is ruined. Good call to everyone who suggested the hub. Off to the prop shop this afternoon, thx again for all the advice.
08-10-2010, 08:00 PM
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It is very common with rubber hub props. I don't think it is the coupler, or it wouldn't move at all. I would bet it is the prop. You may not be able to tell right away. Just pull the prop and take it to a prop shop and have it replaced.
It should only be about $50.
Eddie
It should only be about $50.
Eddie
