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Old 20-04-2017, 21:56   #1
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SD 50 Input Shaft Leak

So both my 1800 hour SD50 input shafts are leaking SD oil.

Had input shaft seals replaced on one SD, but when shaft was removed mechanic discovered a groove had warn into shaft where seals come in contact. Accordingly changing seals didn't stop leak.

So I see my options as

1. Replace input shaft with new input shaft - will I need to re shim input pinion gear? Draw back is that it will only last about 1500 hours or so....

2. Install a speedi sleeve on existing shaft - have been told they don't last as long as a new shaft, but cheaper than buying new shaft.

3. Have a machine shop weld groove with stainless steel, then turn it down to size. This will take longer than options 1 & 2 to complete, but how long will this repair last? Cost would be slightly less than purchasing a new shaft.

So, thoughts on which way to proceed would be appreciated.

Also, does anyone have size (or part number) of a generic input shaft seal, cause Yanmar ones are a little expensive.

Thanks in advance, Brett

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Old 21-04-2017, 14:59   #2
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Re: SD 50 Input Shaft Leak

Sleeve would be my first option while waiting on a new input shaft from Yanmar Japan. Don't waste time welding/grinding the shaft.

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Old 21-04-2017, 21:38   #3
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Re: SD 50 Input Shaft Leak

Find a seal with a thinner profile and/or use a spacer so that the lip of the seal rides on a different part of the shaft.
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Old 22-04-2017, 05:08   #4
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Re: SD 50 Input Shaft Leak

Since I have a lathe and tig welder in my shop I'd personally build it up then turn it down. Would want to take some inspection time at the end to ensure I didn't pull the shaft with the heat from the weld.

If the shaft was clean and ready to weld on I can't see the whole operation taking more than an hour. I'd first set it up between centers or a collet if I had the right size on the lathe. See what kind of runout you have. Then undercut the worn area to get to clean metal. Weld it, turn it down within 0.001" of finish size then polish it to final size. Check with indicator to see if runout is in spec. If not use some spot heat/cooling to pull it back straight.

It's very common to do this for shafts outside the marine world, large electric motors, pumps routinely have this done. I'm not a pro so I can't tell you the answer to this but there is a limit to how small the shaft can be or the heat from welding on it will warp the shaft where it isn't feasible to do this procedure.

So I'd say if you brought to a machine shop, maybe a few hundred dollars max as a guess. I don't know where you live or what the going rate is. Or what a new shaft costs.

There's a guy on YouTube, Keith Fenner. His company is called turn wright machine works. His specialty is marine shafting but he does stuff like this all the time. He's a true old school machinist. I knew him before but not well. I was on a J40 the night before the start to Figawi and the boom snapped in half. Like completely and utterly snapped in half. I called him up Friday Memorial Day weekend at 6pm sailing into Hyannis. By 10 pm we were driving back to the boat with the boom completely and expertly repaired. Skipper is still running it that way 2 years later. Might want to give him a call see if he'd take it on for you.
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