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Old 07-26-2010, 05:55 PM
MikeR MikeR is offline
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Shaft coupler stuck

Hi,
Complete V-drive Newb here-- just upgraded to a 2001 X-30 with 280 hours on it from a 1989 Mercruiser I/O. I worked on the I/O a lot, but have never worked on a V-drive boat before, so I'm new to these beasts and their idiosyncrasies.

We love the new boat, but it has a few quirks that I've got to iron out.
I discovered that it takes 2 hands to turn my prop when in neutral, so I figured it was an alignment issue (there doesn't seem to be any vibration when running, some "gear noise" at idle and intake "whining" at high speeds-- but from I read these are normal)

I tried to undo the coupler to check alignment, but when I got the bolts off I could not separate the two halves of the coupler--no gap anywhere around. So I wimped out and took it to a mechanic. He didn't separate the coupler, but told me the shaft is bent (by using a straightedge maybe?) Is it possible to have a bent shaft but little/no vibration?
I'm unsure of the mechanic's answer now, so I might have to get back into it myself.

How do I separate coupler halves that are stuck together? What can I "bang on" without damaging bearings, etc. Do I hit the end of the prop shaft and try to drive the shaft forward in the boat and the coupler halves apart? Or do I try to pound a wedge/knife edge between the coupler halves in hopes of prying them apart?

I know this coupler stuff and alignment has been covered extensively in these forums, but I haven't seen anything on stuck coupler halves.

Thanks for any help you've got.
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  #2  
Old 07-26-2010, 06:35 PM
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Chicago190 Chicago190 is offline
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I had this problem in the spring when I checked my alignment. I soaked the coupler in PB blaster for a few hours and then took a wood block and mallet and firmly whacked the coupler on the shaft side (the shaft has some play available unlike the transmission side). I would hit it and then spin the shaft 90 degrees and repeat. I then went under the boat and pulled on the prop towards the rudder. It separated after that.
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Old 07-27-2010, 09:15 PM
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brettmess24 brettmess24 is offline
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If your shaft is indeed bent make sure to check the strut as well. You can remove the prop and tap the end of the shaft to separate the coupler, should come right off. Now the shaft nut is another story!

And yes it is possible to have a bent shaft with minimal vibration.

Last edited by brettmess24; 07-27-2010 at 09:17 PM.
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Old 08-13-2010, 11:43 AM
MikeR MikeR is offline
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Second mechanic has different answer

Thanks for the advice on separating the stuck couplers-- with a bit more thought on the subject I realized that the coupling takes the entire thrust of the prop under power, so I shouldn't be worrying about damaging transmission bearings by hitting on the end of the prop shaft a bit to separate the coupler.

We asked around a bit, and found that the first mechanic wasn't really a V-drive expert, he's better with I/O and outboards. So we went to a second mechanic who's highly recommeded for high end ski boats. (since we're new to the whole V-drive thing, I wanted to get a clean bill of health from an expert in case there's things I just don't know to look for, then hopefully I'll be able to handle it from here on out)

Anyway, the second mechanic said that the strut bearings can sometimes be a bit tight (which he said explained the prop shaft being hard to turn in neutral). But he said that everything is fine, no bent shaft!

I *like* his answer a lot more, but there's a lot of people on this forum who say the prop shaft should be easy to turn. Not quite sure if I should believe the new mechanic either-- guess if you want something done *really* right you've gotta do it yourself. So I think I'm just going to leave it alone for the rest of this season, since it seems to run really smooth (no vibration); and next season I'll pull the coupler apart and see if I can align it better than the mechanic and get a more freely spinning prop shaft.
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Old 08-13-2010, 12:30 PM
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oldairboater oldairboater is offline
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Being a country boy and having grown up working all kinds of boats I picked up some simple tricks. I worked on boats every summer and after school for my first real job. Take a welding rod and tape it to a reference point that doesn't move. Turn prop slowly and easy by hand. If shaft is bent it will show. Application of turning force needs to be a constant in location and pull. We also do this for propellers large and small. We just find a different reference point to secure to near whatever we are using to see wobble. You can sometimes locate the bend doing this by moving reference rod up or down the shaft. If you see wobble that makes sense then it is time to break out the tools or get a better opinion. We it comes to alignment I would make sure that I have a alignment problem before I create a alignment problem.

Last edited by oldairboater; 08-13-2010 at 12:33 PM.
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Old 08-13-2010, 01:13 PM
FrankSchwab FrankSchwab is offline
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If the strut-to-engine alignment is off, then it will force a bend in the driveshaft. If you check straightness with a straightedge, you'll probably be able to pick it up. However, if you check using a oldairboater's technique (or with a higher-tech dial indicator), you won't see it - the shaft won't "wobble" as it turns, but it'll be bending back and forth all the same.

I still recommend doing the propshaft alignment; if you seperate the coupler, I think your problem will become obvious - the shaft side will move relative to the transmission side.

/frank
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Old 08-13-2010, 01:27 PM
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oldairboater oldairboater is offline
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Double post I was thinking too hard.
Quote:
Originally Posted by FrankSchwab View Post
If the strut-to-engine alignment is off, then it will force a bend in the driveshaft. If you check straightness with a straightedge, you'll probably be able to pick it up. However, if you check using a oldairboater's technique (or with a higher-tech dial indicator), you won't see it - the shaft won't "wobble" as it turns, but it'll be bending back and forth all the same.

I still recommend doing the propshaft alignment; if you seperate the coupler, I think your problem will become obvious - the shaft side will move relative to the transmission side.

/frank

Last edited by oldairboater; 08-13-2010 at 01:32 PM.
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Old 08-13-2010, 01:31 PM
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oldairboater oldairboater is offline
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Welding rod is a quick simple trick and saves me from dragging out indicators. I can see how couple alignment would be easier to see with split couplers but a dial indicator should detail any lateral movement in a shaft if the shaft is bending anywhere. Bend back and forth isn't a wobble that a dial indicator would see? What am I missing?
Quote:
Originally Posted by FrankSchwab View Post
If the strut-to-engine alignment is off, then it will force a bend in the driveshaft. If you check straightness with a straightedge, you'll probably be able to pick it up. However, if you check using a oldairboater's technique (or with a higher-tech dial indicator), you won't see it - the shaft won't "wobble" as it turns, but it'll be bending back and forth all the same.

I still recommend doing the propshaft alignment; if you seperate the coupler, I think your problem will become obvious - the shaft side will move relative to the transmission side.

/frank
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Old 08-13-2010, 04:06 PM
FrankSchwab FrankSchwab is offline
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Take a straight shaft. Attach something to each end - say, an engine on one side, and a prop on the other. Bolt the engine to something solid. Now, move the prop six inches to the right, and bolt it to something solid.
If you look at the shape of the shaft, it will be bowed - it has to be to get from where it wants to be (straight back), to where it is (six inches right). If you rotate the shaft, the bow will stay in the same place relative to the boat (it won't "wobble"). If you put a straightedge on the shaft, you'll see the bow and can measure the 6 inches. However, if you attach a dial indicator (or welding rod) to the boat to check for straightness and rotate the shaft, there won't be any wobble - the shaft will always bend the same amount when measured at the same location. If you disconnect the engine and the prop, the shaft will now spring back into position, and be perfectly straight again.

If the shaft was bent before you started all this (i.e. with no forces on it), then using the dial indicator or welding rod will tell you that - you'll be able to see the bent spot as it rotates; it'll "wobble".

At least that's the way I understand it.

/frank
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Last edited by FrankSchwab; 08-13-2010 at 04:12 PM.
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Old 08-13-2010, 09:19 PM
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brettmess24 brettmess24 is offline
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Miker, that sounds right to me, try moving the prop right after you pull it out of the water. If the prop turns easier and you feel smooth rotation I wouldn't worry.


Now when you are done for the season listen to what FrankSchwab is saying as he is spot on. You sound like you have some experience with mechanics and once you read the engine alignment threads on this forum it will all click.

Have fun

Last edited by brettmess24; 08-13-2010 at 09:23 PM.
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