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Prop shaft run-out

Old 06-24-2022, 10:08 PM
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Default Prop shaft run-out

What allowable runout for a standard Bravo prop shaft. Last weekend a submerged log jambed between the prop and cavitation plate. When I put it in reverse it stalled the motor instantly. Found the cavation plate broken. Checked the shaft and have .0035-.004 runout towards the end of the splines. Up close it's out about .002.



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Old 06-25-2022, 06:21 AM
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Most say .005 is max, with .0035 or under preferable.
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Old 06-25-2022, 12:13 PM
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Originally Posted by bajaman View Post
Most say .005 is max, with .0035 or under preferable.
Ayuh,..... At the aft end of the shaft, the threaded end,....
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Old 06-25-2022, 07:36 PM
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Clean the shaft up and polish it with 220 Emory. And you probably have a run out of .005
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Old 06-26-2022, 06:49 AM
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Which leads us to the next question; Can it be straightened with a block of wood and a BFH?
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Old 06-26-2022, 07:03 AM
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No and why? You stated .0035. Spec is .005
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Old 06-26-2022, 07:36 AM
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Originally Posted by thirdchildhood View Post
Which leads us to the next question; Can it be straightened with a block of wood and a BFH?
Small bottle jack. Keep dial indicator on to measure deflection. Probably not the right fix(replace shaft) but can be done.
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Old 07-06-2022, 09:03 AM
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Old 07-06-2022, 09:09 AM
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This was our test for an insurance claim, was tested on the drive by the adjuster, he showed. 006, within spec, but did the test behind the splines, we pulled it apart, checked it as you see it, claim reversed

If it's out of spec, replace it, no way I would ever try to bend it back, you could damage bearings and a whole lot more trying to safe a few bucks
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Old 07-25-2022, 02:51 PM
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I would inspect your gears, you may have cracked a tooth. I had a similar situation, except no visible damage until you pulled the prop off. Inspected everything in the water after I felt a thump, no visible damage so I kept boating. Prop shaft and vertical shaft both had a twist in the splines. I found that out after the drive grenaded and I pulled it off to get repaired. Lesson learned, when you feel a thump, pull the prop.
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