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Old 08-18-2015, 07:51 AM   #1
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Engine Hours and Shaft Wear

We purchased a 1987 vessel with a bit over 1300 showing on the engine hour meter. Since the boat was primarily used as a stationary houseboat for the past decade, I could believe that the hours were correct. Boat ran smooth as silk on sea trials despite broken engine mount and the fact that only two bolts were tight in the coupling and one was missing entirely (this discovered after the surveyor left).

Now we are getting into the shafting and have discovered this wear. It's making me wonder about that engine hour meter. OTOH, this boat has an enclosed shaft log with no way for water to lubricate it other than working its way in through the bearing from the back. I hope this, and the lack of any flow to flush out silt, is the cause of the wear and not the fact that we have engine hours commensurate with this level of wear.

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Old 08-18-2015, 08:10 AM   #2
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Not sure the shaft wear is any worse than many I have seen...and a little wear on a larger shaft, on a low powered trawler with no corrosion there should not be worrisome either....other than keeping a snug cutless bearing.

Not sure of the setup...but if similar to a lot of single shaft trawlers....you could add a water injection stuffing box....but as long as the lower bearing casting hole are kept open...I doubt it would be a big help.
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Old 08-18-2015, 08:18 AM   #3
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The casing holes were filled in some time in the boat's past. I am adding a water injection stuffing box as we'll be doing a lot of shallow water work and I want to positively flush silt out of the shaft log.

Also, insuring a good flow of freshly oxygenated water is the best insurance against the crevice corrosion and pitting we found in the bearing and sealing surfaces.

BTW, according to my guy on the spot and the yard owner, it's worse than the photo indicates.
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Old 08-18-2015, 08:31 AM   #4
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My casual attitude of the wear is that many of us run our engines at significantly reduced power.

My shaft is 1.5 inches coupled to a 120 Lehman....the same diameter that was on my sportfish, with 320 horse Cats.

Assuming a little wear on all shafts and retaining a safety margin...I would think it could be quite a bit of wear before failure is a concern...like I posted...it is more about getting a cutless to work more than anything.

If an issue...my shaft got some sort of coating at a machine shop to fill pitting and the wear area. I was having a split coupling fitted so the charge was only a couple hundred on top of the total bill.
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Old 08-18-2015, 09:39 AM   #5
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Well, maybe some good news. Now that the shaft is out, the yard owner thinks both it and the coupling may be salvageable. They are going off to a local prop shop for checking.

There is room to shorten the shaft log tube a couple inches in order to bring the packing onto an unworn part of the shaft and away from the pits we found there. We'll be operating this boat 95% of the time at less than half the power the shaft was designed for so I'm not concerned about retaining full strength.
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Old 08-18-2015, 10:10 AM   #6
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Old 08-18-2015, 10:13 AM   #7
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Great News Roger !!
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Old 08-18-2015, 04:06 PM   #8
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A couple of interesting videos of a small machine shop repairing a propeller shaft. It is three part;

https://www.bing.com/videos/search?q...67D398C968266F



https://www.bing.com/videos/search?q...48F2E37EE41191

https://www.youtube.com/watch?t=80&v=1ZHMogAJK-c
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