On my last cruise, I picked up a vibration on my port side above 1,000RPM. There is no indication of striking anything or apparent prop damage. My cutlass bearings were inspected OK at last haul-out in May; I had a small ding repaired and port prop successfully balanced at that time. There is no indication of gear issues. So, I'm going in two directions. I'm going to break the shaft/gear coupling and check the alignment because I've always had just a bit more vibration (well within acceptable limits) on that side than starboard. I'm also looking at possibly a cylinder (injector) dropping out. I'll be looking at that probably before I look at the shaft, as I really doubt anything there has changed.
My question is this: What would we consider to be the allowable tolerance for shaft alignment? The shafts are 2-1/2", btw.
Thanks for your input.
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Thread: Shaft Alignment Tolerances
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Shaft Alignment Tolerances
Semper Siesta
Robert Clarkson
ASLAN, 1983 55C #343
Charleston, SC
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12-23-2019 07:19 PM #2
Re: Shaft Alignment Tolerances
Not my area of expertise.... but there's a good current discussion here... and sounds reasonable..
https://www.downeastboatforum.com/threads/tolerenace-for-propeller-shaft-alignment.27046/
Fifth post down on that thread.... 0.001" for each inch of shaft diameter plus 0.002"...
Have you checked motor mounts?
JD
1976 58' LRC Hull #311
"Miss Maggie"
Riviera Dunes, FL
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12-23-2019 09:04 PM #4Senior Member
- Join Date
- Jan 2006
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- 822
Re: Shaft Alignment Tolerances
.003 is considered the outer tolerance. I usually set the gap, if any, at the top since the mounts seem to settle more in the rear, over time.
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12-23-2019 10:52 PM #5
Re: Shaft Alignment Tolerances
Mine had a vibration and found about 10' of cast net rope with lead molded around it on the shaft.
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Re: Shaft Alignment Tolerances
When you say "no apparent" prop damage. How did you inspect the prop? Did you measure the path of each blade against a fixed point?