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  #1   IP: 108.51.19.207
Old 09-15-2020, 07:43 PM
svsonora svsonora is offline
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Propshaft alignment with split hub - visible movement

I'm using a
1. new shaft
2. new split coupler
3. new shaft bearing

The shaft is 20 inches long, going into a direct drive transmission. Vessel is a Bristol 30 with a hard-mount (e.g. shim aligned).

The old prop shaft and coupler exhibited no vibration or other problems, despite a worn out shaft (cutlass) bearing.

Things I did that might have been out of the ordinary - I loosely bolted on the coupler, with a few threads of play. I aligned the key, hub and shaft and lightly tapped the shaft into the coupler from the outside with a rubber mallet. Then I tightened the hex bolts and set screws, then tightened the hub onto the output coupler. I did not reface the coupler - I imagine that was done before I ever got the coupler.

There is visible movement of the shaft - the stuffing box moves a bit when I crank on the engine. Its enough to be visible on a cell phone camera (and more visible in person).

I'm trying to avoid having to realign the engine.
What can I try? I already tried loosening up the stuffing box and the hose clamps and re-bolting the coupler. I don't think its prudent to install a flex coupler in between. I could try removing the shaft, then bolting down the coupler firmly onto the output coupler and then re-installing the shaft. Or perhaps I should try reusing the old coupler? Boat is on the hard.

thanks in advance. (I'm so happy Moyer Marine exists so I can keep my old engine running!)
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  #2   IP: 71.215.209.38
Old 09-15-2020, 08:27 PM
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romantic comedy romantic comedy is offline
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In my experience the cutlass bearing is hard mounted to the hull so the shaft must pass thru in only one position. The shaft is supported by the engine and the cutlass only. The cutlass cant move to position the shaft so the engine must be moved. I see no other way.

Many times the cutlass bearing is worn because the shaft was not aligned- engine was not aligned. Sometimes you can see the cutlass worn on one side from misalignment.
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  #3   IP: 108.51.19.207
Old 09-16-2020, 12:15 AM
svsonora svsonora is offline
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Thanks. Any chance that my coupler was misaligned to the shaft when I tapped it in?
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  #4   IP: 108.185.228.107
Old 09-16-2020, 03:01 AM
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Quote:
Originally Posted by svsonora View Post
Thanks. Any chance that my coupler was misaligned to the shaft when I tapped it in?
Did you use a feeler gauge?
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  #5   IP: 108.51.19.207
Old 09-16-2020, 03:32 AM
svsonora svsonora is offline
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No. I'm going to try it next time I'm at the boat.

I wonder if I ruined the output coupling when I was trying to pop off the old shaft from the old coupler. I'd give the bolts about a turn, rotate, turn, rotate..
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  #6   IP: 24.152.132.140
Old 09-16-2020, 08:05 AM
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How the shaft rotation appeared previously with a worn strut bearing doesn't mean the alignment was correct. What matters is that it is correct now. You can't draw conclusions on what might be off unless you carefully align it yourself.

To that end my suggestion is to remove the stuffing box and its connecting hose. With the new shaft in place in the new strut bearing, center it with small wedges in the inboard end of the shaft log and align the engine using a feeler gauge as suggested by others. Only then can you perform a meaningful test. Once every thing is resolved the stuffing box is reinstalled.
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prior boats 1987 Westsail 32, 1970 Catalina 22
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Last edited by ndutton; 09-16-2020 at 08:10 AM. Reason: punctuation
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