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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 11-21-2010
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Getting the Shaft?

How smooth should a nice new drive train spin--by hand and under power? Last spring I got a new drive shaft, split coupling, cutlass bearing and PSS dripless seal installed by the local Yanmar shop. My goal was to finally have an aligned drive train, taking care of some bad work done for the PO.

While the shaft has been somewhat smoother than before, I was expecting a nicely spinning shaft with very little wobble, but there is quite a bit of runout (to my ignorant eye), and I even see some "wobble" in the PSS metal collar when I simply turn the shaft by hand. Also, I've now got a tick tick tick sound in the shaft somewhere that is pretty annoying.

I already had the shop come back to check the alignment and they said they did have to change things some, but it seems no better to me. Still has wobble, still makes noise.

Am I expecting too much, or is something wrong in there? How smooth should a 1" shaft spin with a Yanmar 2GM20F at one end and a 2-blade prop at the other? Should the PSS turn in a lopsided way when I turn the shaft by hand? Forgot to mention, there's a Drivesaver between the coupling and tranny--they pulled that and went metal to metal to do the alignment, and then put it back.

Thanks!

Tom
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Old 11-21-2010
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Are you observing this same 'runout' at speed? Many smallish engines tend to 'hop around' on their soft mounts at idle speeds but settle down at load.

You don't mention leakage so presumably the seal is not being broken.
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Yes, I see it at speed. At a nice 2000 rpm, which is pretty smooth engine-wise, if you put your fingertip against the shaft it bumpts it pretty good.

Actually, we did have some leakage at the dripless. The installer came and increased tension twice. I don't think you could put any more tension on it now. It was when they did this the second time that made me think the alignment was causing the leakage and not just tension on the bellows, so I had them come out and realign.
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Old 11-21-2010
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That does sound like an alignment issue.. or a 'wow' in the "new" shaft - which would be rather annoying! Doesn't sound right, either, that you "don't think you could put any more tension on it now"

Looks like you're back to the basics... btw you're up late!
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Old 11-22-2010
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Suggest you re-allgn the engine and check the shafting to be sure that it is 'true' - take the shaft to a machinist and get any 'runout' (small bends in the shafting) corrected. Runout (developed bends) can appear any time a shaft is in service due to 'strain relief' of the material.

This time start your alignment with the packing removed and with the coupler disconnected -
First center the shafting in the CUTLESS .... 'orbit' the end (engine/front end) of the shaft to ensure that the shaft is in parallel to the cutless and 'block it' in place when you find the center and then assay if it is in the exact CENTER of the stuffing box. Make corrections to the alignment of the stuffing box if needed. This is important as if the shaft is not in the 'dead center' of the packing box, tightening down on the shafting with packing when not 'centered' will impart 'side loads' which will induce 'shaft whip' (and 'knocking' due to 'shaft whip' when the shaft is rotating at high speed). Then once the shaft is true and parallel (and still blocked in place), align the engine TO the shaft.

If the shaft is not parallel in the cutless, you will risk enhanced wear due to high friction of the shaft against the cutless bearing ... a shaft has to be parallel (true) inside of a cutless. You may need to also 'realign' the strut if the shaft is not exactly parallel to the cutless in severe misalignment situations.
Any component of the propshaft system that is not aligned and that imparts 'side loads' or 'twists' to the shaft can easily be the cause of 'shaft whip'.
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Up late thinking about it! Back to basics is not good at this point

But just so I am sure, if you have all new drive train gear like I have, and you turn the shaft by hand--which is something like 10 rpm--should the PSS collar turn nicely, and appear to be perfectly perpendicular to the shaft? That is no "wobble"?

What I am thinking is to have someone else come take a look--if I can find someone I trust--though of course, that's more $$$.
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Old 11-22-2010
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The simple/easy solution would be to break the coupler loose and see if the shaft can be rotated easily by hand ... and where does the shaft when free at the coupler 'equilibrate its relative position in relation to the engine.

I just noticed that you have a P28 .... and these hulls are 'floppy' and can grossly distort when the boat is on the hard if improperly blocked. If this boat is on the hard when you are having difficulty turning the shaft ... it may be that the boat is improperly blocked ... and you will also see large 'dimples'/deflections in the hull aft of the keel. ???? in the water or out ???? All Pearsons (1970s through '89) need to be IN the water to check alignment - IMHO
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Quote:
Originally Posted by RichH View Post
I just noticed that you have a P28 .... and these hulls are 'floppy' and can grossly distort when the boat is on the hard if improperly blocked. If this boat is on the hard when you are having difficulty turning the shaft ... it may be that the boat is improperly blocked ... and you will also see large 'dimples'/deflections in the hull aft of the keel. ???? in the water or out ???? All Pearsons (1970s through '89) need to be IN the water to check alignment - IMHO
D'oh... that's an obvious question although arf did indicate observing at 2000 rpm so I assumed the boat was afloat.. but that's a great point and very important to this situation. Even so, the PSS collar should not visibly wobble at any time....

Assuming hull distortion is not at play the shaft should turn evenly by hand with no 'hard' spots, esp if decoupled. (if there's a folding prop you will feel the blades flop around)
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Old 11-22-2010
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Quote:
Originally Posted by arf145 View Post
Forgot to mention, there's a Drivesaver between the coupling and tranny--they pulled that and went metal to metal to do the alignment, and then put it back.
It's been about 10 years since I did all the same operations with my previous boat, but making the adjustments with the Drivesaver (plastic doughnut) out of the picture and then adding the Drivesaver back in doesn't seem right to me. That's making the assumption that that piece of plastic is 100% true and is having no affect on the alighnment - Bad Assumption to my way of thinking.
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The boat is in the water and has been all season--nicely relaxed. The initially alignment after all the work last winter (when she was on the hard) was done when she had only been in the water for a day or so. I thought they had jumped the gun a bit, and I figured the later re-alignment would fix this.

RichH, I've read about the many steps to get a proper alignment, but that stuff is beyond my capabilities. The guys I hired were supposed to be doing all that!

ChristyLeigh, I am beginning to wonder about the Drivesaver. But if you are going to have one in the drive train, you can't use a feeler gauge against the plastic. So more than one shop has specified the remove/reinsert method. But now I'm wondering if an old (> 20 yr) Drivesaver can be the problem?

And BTW, does everyone agree that it is a problem that turning the shaft by hand has the PSS collar turning less than true?

Thanks for your help!
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