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  #1   IP: 192.60.230.125
Old 04-13-2009, 01:21 PM
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Bad cutlass chatter?

Help!

The last time I revved up my A4 in the water, I hit about 1600(?) rpm and the engine seemed to shudder or balk at going any higher. As well as I can remember (I've only had the boat out a few times) this is the speed at which the prop starts to cavitate. In the past, the engine kept revving up in speed and the boat didn't go any faster. I don't remember this new shudder sound. It is as if the engine power hits a wall and cannot proceed any faster. It starts to stall. When I back the throttle down, it resumes its normal operation.

The boat is now out of the water. I have discovered that the same thing happened when I ran the engine on the hard. I don't know for sure if the prop was spinning, but I later discovered that the reversing gear wasn't quite in neutral.

I can wobble the drive shaft in its cutlass bearing in all directions quite a bit. I know this isn't good. I am thinking that the prop shaft starts to rattle inside the bearing at just the right speed and that this adds a lot of friction against the rotation of the shaft because the shaft is slamming into the cutlass bearing sleeve in all directions.

Is anyone familiar with this type of failure? Am I on the right track? Or is this not a cutlass issue?

Steve
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  #2   IP: 70.62.136.139
Old 04-13-2009, 02:05 PM
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It could be the cause of your problems; it's certainly contributing. Regardless, the cutlass bearing needs to be replaced. Also, you want to check for reasons for cutlass bearing failure. Of course, they do wear out, but will wear prematurely if the shaft is not true, out of alignment, or the prop is out of balance. Replacing the bearing is not a hard DIY job, but you may want your marina mechanic to do it if you need to check the other things and are not comfortable doing the other checks.
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1977 c&c30 Mk1 hailing from Port Clinton, Ohio
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  #3   IP: 70.108.226.198
Old 05-19-2009, 10:08 PM
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Hi Mark,

I just wanted to follow up. I replaced the cutlass bearing and all is well. A few notes: While on the shore and after the new bearing was installed, I experienced the same chatter when the prop was turning very slowly. The reversing gear was in neutral, but as you are aware, the prop tends to twist slowly. When I stopped the prop, the noise ceased.

Once in the water, the chatter stopped completely.

I was surprised to see how loosely the bearing fit on the shaft. I had imagined that this would be a tight fit.

Thanks for your help. I appreciate it.

Steve
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  #4   IP: 71.66.237.123
Old 05-20-2009, 08:51 AM
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glad this worked out, and if I have an electrical question, I know who to ask.
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1977 c&c30 Mk1 hailing from Port Clinton, Ohio
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  #5   IP: 70.108.190.101
Old 05-20-2009, 10:05 AM
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Any time.


(need more words to post this - ignore)
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  #6   IP: 72.71.249.221
Old 05-20-2009, 10:28 AM
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Don't run the propshaft in a dry condition, your prop shaft will act like and eraser on your new cutless bearing. The cutless bearing uses water as a lubricant.

If you absoutely need to turn the prop with the engine when on the hard. Number one, make sure that no one is near the turning prop and number two have a large amount of water directed at the cutless bearing.

Safetly first.

David
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