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Old 05-24-2021, 08:01 PM   #1
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Split shaft coupling question

Busily installing my new water maker today and crawling around the engine room I noticed that my port side shaft is not fully engaged with my split shaft coupling -- yikes! On the starboard side the key is about flush with the coupling & the shaft is far enough into the coupling as to cover the split entirely.

I'm embarrassed that I didn't see this sooner. I have to believe it's been like this since I bought the boat a year ago (and had her surveyed); as the PSS shaft seal would be overly compressed if it had slipped recently - its compression matches the starboard side.

My thought is to loosen the pinch bolts and the PSS set screws and slide the shaft in until it bottoms (fingers crossed!), replace the bolts with new grade 8, button everything up, and maybe paint the whole unit. I thought I'd check in here before I screw anything up though!
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Split shaft keyway.jpg   Split shaft gap.jpg  
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Old 05-24-2021, 08:15 PM   #2
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Do you have enough shaft to be able to pull it forward? On my boat it wouldnít pull forward without hitting the strut.
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Old 05-24-2021, 08:31 PM   #3
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Do you have enough shaft to be able to pull it forward? On my boat it wouldnít pull forward without hitting the strut.
Good point. Might need to dunk my head underwater with a mask to check that first. Previous owner put in new shafts, props, cutlass bearings; I wonder if one of the shafts was cut 3/4" short...
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Old 05-24-2021, 08:42 PM   #4
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Or the shaft may had slid aft some if it is slipping in the coupler. Certainly something to check before you get underway next time.
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Old 05-24-2021, 08:49 PM   #5
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I would recommend a quick haulout to clean the bottom and to check you under water gears. any repairs or adjustment can be performed in the water.
good luck,
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Old 05-24-2021, 08:51 PM   #6
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Think you got it covered after the head dunk.
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Old 05-24-2021, 09:21 PM   #7
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Thanks all. The water’s still pretty cold but better than a $500 haul out! I’ll let you know what I find.
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Old 05-24-2021, 10:32 PM   #8
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Do you have propeller/shaft rope cutters on your boat? Any chance someone may have slid that forward to get enough clearance to install them? Just a totally random thought from the peanut gallery. I guess you'll see when you go for a dunk! Enjoy!
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Old 05-24-2021, 10:59 PM   #9
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Do you have propeller/shaft rope cutters on your boat? Any chance someone may have slid that forward to get enough clearance to install them? Just a totally random thought from the peanut gallery. I guess you'll see when you go for a dunk! Enjoy!
Good thought, but no cutters on the shaft.
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Old 05-25-2021, 03:05 AM   #10
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And I would eliminate the DriveSavers you have installed. Why? When doing the Loop a few years ago, I blew out the DriveSaver, at different times, on both shafts. And, no, I did not hit anything in the water. The first time it was in Canada and I was laid up for a week waiting for new Drivesaver over the Canada Day, Fourth of July holiday period. The second time was on Christmas Eve day. We limped into Fort Myers in the waning light after 45 slow miles running on one engine. After that second incident the boat went into a yard. No more DriveSavers for me!
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Old 05-25-2021, 10:03 AM   #11
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Our boat had Drivesavers on it. Too much vibration since we couldnít do a proper alignment. Replaced the Drivesavers with spacers from Spurs, no more vibration.
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Old 05-25-2021, 10:11 AM   #12
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And I would eliminate the DriveSavers you have installed. Why? When doing the Loop a few years ago, I blew out the DriveSaver, at different times, on both shafts. And, no, I did not hit anything in the water. The first time it was in Canada and I was laid up for a week waiting for new Drivesaver over the Canada Day, Fourth of July holiday period. The second time was on Christmas Eve day. We limped into Fort Myers in the waning light after 45 slow miles running on one engine. After that second incident the boat went into a yard. No more DriveSavers for me!
Jack, please expand on why you did not just remove the broken drivesaver and couple together the shaft as it was before DS was installed. You are talking about these that fit in between tranny and shaft.
https://www.globecomposite.com/drivesaver
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Old 05-25-2021, 11:17 AM   #13
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I’m hesitant to eliminate the DriveSavers as one saved my bacon last year when I wrapped a mooring line on my prop! But I have heard of these issues.
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Old 05-25-2021, 12:06 PM   #14
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Quote:
Originally Posted by socalrider View Post
Busily installing my new water maker today and crawling around the engine room I noticed that my port side shaft is not fully engaged with my split shaft coupling -- yikes! On the starboard side the key is about flush with the coupling & the shaft is far enough into the coupling as to cover the split entirely.

I'm embarrassed that I didn't see this sooner. I have to believe it's been like this since I bought the boat a year ago (and had her surveyed); as the PSS shaft seal would be overly compressed if it had slipped recently - its compression matches the starboard side.

My thought is to loosen the pinch bolts and the PSS set screws and slide the shaft in until it bottoms (fingers crossed!), replace the bolts with new grade 8, button everything up, and maybe paint the whole unit. I thought I'd check in here before I screw anything up though!
Things may not slide as easily as you hope but having the shaft only on the split is not right, will be prone to stress cracks.

On my shaft/coupler interface there is a steel cross-pin that is an interference fit holding the shaft in place to the split coupler in addition to the two bolts of the split coupler. The pin has to be driven out before you can slide the shaft at all, it looks like yours does not have that feature.

In addition to verifying space on the outside of the hull, I would verify that you are able to get the PSS loose and sliding before unbolting the split coupler, better to know you can keep pressure on the face seal before you start trying to slide it around. Keep in mind there are TWO set screws, one on top of the other on the PSS, remove the outer one and then loosen the inner one. Use blue loctite on re-assembly, ibelieve PSS recommends replacing the set screws each time. You may already know that but if you don't it can lead to a frustrating time.
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Old 05-25-2021, 01:54 PM   #15
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Pull ONE of the pinch bolts that close the split.

I think you will find that the shaft sides are dimpled about 1/8 of the bolt diameter to accommodate the pinch bolts which are set into the shaft sides.
The shaft will not move unless both of those bolts are pulled or broken.

The fact that the installation shows a different depth is curious but I don't think you need panic. At next haulout then check it further.

I would though check the bolt size and grade, then look up the torque and check that also.

I use Nev R Seez [or something similar]on the bolts, and the shaft and coupling bore. Not gobs of it, just a light smear.
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Old 05-25-2021, 02:16 PM   #16
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Pull ONE of the pinch bolts that close the split.

I think you will find that the shaft sides are dimpled about 1/8 of the bolt diameter to accommodate the pinch bolts which are set into the shaft sides.
The shaft will not move unless both of those bolts are pulled or broken.

The fact that the installation shows a different depth is curious but I don't think you need panic. At next haulout then check it further.

I would though check the bolt size and grade, then look up the torque and check that also.

I use Nev R Seez [or something similar]on the bolts, and the shaft and coupling bore. Not gobs of it, just a light smear.
The second picture appears to show that the shaft is only inserted into the split part of the coupling, and is not engaged with the solid part at all. If that's the case, I would want it corrected sooner than later, all of the forces of the shaft are being transmitted through the split part only and this can contribute to stress cracks propagating from the split area.

The bolts clamping the split are rusty enough that you can't make out any grade marks unfortunately so I'd probably replace them while doing the rest of the work.
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Old 05-25-2021, 06:39 PM   #17
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The second picture appears to show that the shaft is only inserted into the split part of the coupling, and is not engaged with the solid part at all. If that's the case, I would want it corrected sooner than later, all of the forces of the shaft are being transmitted through the split part only and this can contribute to stress cracks propagating from the split area.

The bolts clamping the split are rusty enough that you can't make out any grade marks unfortunately so I'd probably replace them while doing the rest of the work.
I missed that.
I agree that the shaft should go further into the coupling, to the end of the solid part of the coupling.

Hmm, looks like a haulout will be needed.
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Old 05-25-2021, 10:29 PM   #18
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Thanks again all. I'll pull a single pinch bolt to see if the shaft is dimpled per C lectric. If so, that would mean the install was totally botched. If not, it seems I should be able to do this in the water though, right? Curious how those dimples get machined into the shaft & whether it'd be possible in situ.

sbman, good tip to get the PSS free prior to moving the shaft. I figured that one out the hard way when I blew up my Drivesaver - they are not easy to move on the shaft.
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Old 05-26-2021, 12:06 AM   #19
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Thanks again all. I'll pull a single pinch bolt to see if the shaft is dimpled per C lectric. If so, that would mean the install was totally botched. If not, it seems I should be able to do this in the water though, right? Curious how those dimples get machined into the shaft & whether it'd be possible in situ.

sbman, good tip to get the PSS free prior to moving the shaft. I figured that one out the hard way when I blew up my Drivesaver - they are not easy to move on the shaft.
From my understanding, all the machining to fit a coupler to a shaft is done in a shop. There is a local company in San Diego that is known for good work on driveshaft work, I'll get the name of the place if you need them. If you have enough clearance at the shaft/strut/prop interface to move forward, should be able to scoot things around in the water, but it's really hard to apply any force all from inside the boat. When I put mine together, I used a couple of wooden blocks to tap on the end of the shaft under the boat to help push it into the coupler, it was a fairly tight fit.
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Old 05-26-2021, 12:26 AM   #20
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From my understanding, all the machining to fit a coupler to a shaft is done in a shop. There is a local company in San Diego that is known for good work on driveshaft work, I'll get the name of the place if you need them. If you have enough clearance at the shaft/strut/prop interface to move forward, should be able to scoot things around in the water, but it's really hard to apply any force all from inside the boat. When I put mine together, I used a couple of wooden blocks to tap on the end of the shaft under the boat to help push it into the coupler, it was a fairly tight fit.
Thanks - that sounds like an interference fit coupling? I'll let you know if I need the driveshaft work done - still holding out hope I can resolve this in the water with pry bars, blocks, c-clamps, mallets and beer. I can turn the shaft by hand at least, so I think if I remove the coupling and re-seat it fully onto the shaft I should be able to lever off the back side of the coupling face to draw the shaft up. I could also get some oversized bolts and use them to draw the shaft up to the transmission.

It sounds pretty easy when I write it out like that...
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