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Old 07-29-2018, 10:32 AM   #1
DDW
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Very tight cutlass bearing - why?

Noticed on survey, the prop is very hard to turn by hand - both hands and its about all I can do. I unbolted the engine coupler and no difference so it isn't shaft alignment. This boat has two cutlass bearings, one forward and one aft in the shaft log. It is the forward one, proven by loosening the set screws, then it wants to turn in the log rather than turn on the shaft.

Some have told me that occasionally cutlass bearings just do this. Other guesses are not enough flow from the water line into the Strong seal (the seal looks fine), or perhaps oil contamination (the water line comes from the transmission oil cooler). No oil is evident, and there does not appear to be water in the transmission. I did not check water flow before hauling.

I will replace them both, but wonder what the source of the problem might be.
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Old 07-29-2018, 10:47 AM   #2
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Alignment of the bearings relative to the shaft would be the first question. Do you know enough history on the boat to know if this is a problem that developed, or one that has always been there? A developed problem would more suggest swelling of the bearing vs alignment.


That said, I had just his problem with my wing engine shaft. I could only turn it with a wrench on one of the bolts, and only then with a pretty hard push. Replacing the bearing solved the problem. We carefully checked alignment, shaft dimensions and straightness, etc. The final determination was made when the old bearing was removed and could not be easily slide over the shaft, where the new bearing slide right over and had proper clearances. The shaft now turns easily. I was told that swollen bearings definitely happen. Not common, but it does happen.
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Old 07-29-2018, 04:57 PM   #3
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One-owner boat until me, issue not noticed before. The log is a single piece of glass tube nearly as I can tell, with a cutlass in each end, so should be in line. I'll know more when I get the forward cutlass bearing out of the log.
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Old 07-29-2018, 05:05 PM   #4
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I have encountered swelled bearings on a number of occasions over the years. Absent misalignment do not rule that out. Also came across a fiberglass boat with an aluminum shaft log that corroded itself onto the prop shaft and made it very hard to turn.
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Old 07-29-2018, 07:33 PM   #5
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Sometimes the rubber in the bearings swells, for some chemical reason. My boat right now has a little of that. Hear it squeak when going into neutral as shaft rpm winds down to a stop. Hard to turn by hand.

I don't worry about it, it will wear itself to a happy place eventually.
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Old 07-29-2018, 10:19 PM   #6
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My shaft is very stiff to turn by hand. I believe it has 3 shaft bearings and the NP 43s are known for having stiff shafts. A mechanic familiar with them said that swelling of the shaft bearings is a common issue and for the most part, a non-issue.
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Old 07-29-2018, 11:53 PM   #7
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On the hard during survey, I had to reef on the prop blades to turn the shaft. Turned out the engine mounts had collapsed about 2". New mounts and realignment, we were good to go, prop would coast to a stop.
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