Periodic terrible growling in transom area over 1800 RPM

harojs

Petty Officer 3rd Class
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Aug 28, 2016
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1995 VP 5.0L with SX-M

Was following another cruiser at 18kts and got into his wash and cavitated briefly. I immediately returned to idle, but I at least red-lined or went over 4400 RPM which is top RPM. Waited to get out of his wash, and then proceeded normally.

However, now periodically once above 1800 RPM I get a horrible growling from the transom area and the engine severely loads down, and prop slows and boat slows. Like something clamped down and squeezed my shaft hard. I immediately went to idle and crawled back to my marina at 5kts. No growling below 1800 RPM. No growling moving sterndrive from side to side.

[Q1] Could the brief cavitation over-rev have caused my gimbal bearing to overtemp, spin out of alignment, or be damaged in some way?

[Q2] Is the sound and behavior lean towards a damaged gimbal bearing?

I plan to get the leg pulled and take a look at the GB, just wanted to compare notes with others. My mechanic did normal full seasonal maintenance removing the leg, and he said the GB looked ok and did not change it out. I have no record of any previous GB maintenance, so it could be old and just failed today. I'll put in a new one regardless.

Any thoughts?

John
Bellevue, WA
 

alldodge

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The one time going above 4400 was not the cause of the failure, it was just the last straw which caused it to show up. Time to do what your planning
 

harojs

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Or, could this periodic seisure/loading be happening in the leg somewhere?
 

Lou C

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Nov 10, 2002
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yep....have you been pulling the drive at the end of each season and doing the normal checks and maintenance? Like checking the bellows for water, gimble bearing for free & smooth movement, u joints for looseness and binding and greasing them if they have grease fittings? The bellows on these last at least 5 years but should be replaced if you see any small cracks starting in the folds.
 

harojs

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Aug 28, 2016
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Yep, leg pulled and inspected all you mentioned, along with GB last winter.

Mechanic at my home marine shop says it might be a "spun prop" - will let you know when they look at it all monday. They may not have inspected the prop for slippage, which is getting old. I'd be happy to buy a new prop ...

[Q] Is there a tool or guage to test, (out of water), prop hub for slippage?
 
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harojs

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FYI - Local prop shop says there is no tool or gauge to check for hub slippage other than punch mark method which has to be checked when it comes out of the water again. ( seems like you could make a jig with a torque wrench ). Prop shop also says they can rebuild "most" hubs, - "it depends"
 

alldodge

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You can use a marker
Mark the prop, take it for a little run and look at it by bringing the drive up
 

harojs

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Local shop determined my prop hub was spun. Was older OEM prop and hub rubber was probably getting old. I'm going to go buy a new OEM prop. The Volvo OEM props come with pressed in hubs, not a hub kit. If I find out how shop determined spun hub on a Volvo prop without marking and testing in the water - I will let you know.
 

alldodge

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If you have a press the hub can be pressed out and new in
 
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