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Old 05-06-2012, 10:58   #1
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Join Date: Jan 2010
Location: North Carolina
Boat: 1984 Pearson 34, Sirena
Posts: 31
Pounding and slamming prop sounds

I'm hoping some of you have some expereince with a problem that came up over the weekend.

My wife, the cats and I were returning from Ocracoke, NC leaving through Nine Foot Slough on a Pearson 34. The weather forcast was for 5-10 on the nose and it was 20 knots plus.

As we got to the area where the sound necks down to the shallows at Nine Foot, we entered some big waves. A set of 3 waves stopped the boat completely, we were hobby horsing badly. I was doing 5 knots before being stopped.

It sounded like the prop was hitting the bottom of the boat as we hobby horsed. I thought all hell was breaking loose. Couldn't shut the engine down or we would have ended up on the sand. As I got out of the pounding waves, turned and raised some sail, the prop pounding sound stopped. It sounded like it came from under the wheel or where the prop leaves the hull. I couldn't see any damage inside the engine compartment.

Thsi happened once before in the same conditions and I dove on the boat later, no visible damage.

So what can be causing the sound? The engine and transmission was new last year and was aligned. Is the cutless loose, worn? Just cavitation? It really did sound like the prop was hitting something on the boat.

We made it home with one seasick cat and I have more grey hair.


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Old 05-06-2012, 11:02   #2
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Join Date: May 2012
Location: Central California
Boat: Catalina 30
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Re: Pounding and slamming prop sounds

Possibly cavitation.

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Old 05-06-2012, 11:05   #3
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Location: Canada, up on Hecate Strait in sight of Alaska
Boat: 50-ft steel Ketch
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Re: Pounding and slamming prop sounds

Sounds like it could be a worn cutless bearing or loose strut. Have you been over the side to take a look?
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Old 05-06-2012, 12:03   #4
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Location: puget sound/ caribbean
Boat: never wrecked a boat while awake or sober
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Re: Pounding and slamming prop sounds

Yes, Sounds like a worn cutlass to me also. When they wear, the hole becomes oblong, and usually the shaft rides in the end it wants to go in. When the boat slammed the waves, it may have forced it over to the other side. The cutlass will go out of round from an un aligned engine. Popping a new bearing in there without aligning the engine is just a temp fix. remove the stuffing box on the inside and be sure the shaft is in the center of the tube when aligning. It is possible ti "mike" the coupling , but still not be aligned. The engine is aligned to the cutlass bearing, not the other way around.
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