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  #1   IP: 208.87.234.202
Old 04-29-2016, 10:16 PM
JimF JimF is offline
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Shaft back in, how worried should I be about alignment

I removed the old shaft coupler (see thread: shaft coupler is a rusty lump) and installed a whole new stuffing box, cutlass bearing and Moyer split coupler and everything seems good, shaft spins fine by hand... but today I ran the motor and put the tranny into gear and got a pretty large amount of vibration and the motor was moving more than I ever remember seeing. Now I am still on the hard as I was when the whole job startted, and thing did seem to smooth out somewhat but it is still more vibration than I ever remember seeing. However, I rarely if ever out the motor in gear when running it on land, so I don't have much to compare to in memory. I have been reading some old threads on alignment and it seems that perhaps things will be different when the boat is back on the water. Could the motor have gotten out of alignment just by removing and replacing the shaft? Is the problem likely to go away after launching due to the bottom changing shape (no longer resting on the keel, like it is now). This is a Ranger 29 with very bad access to things like shafts and motor mounts. Also I know nothing about doing a shaft alignment, is this even possible in the water if it becomes necessary? How much vibration is too much, how do you measure these things . Lots of questions. in water and in gear, things were pretty smooth in the past. I am really unsure of what to do with this problem. If i decide to play with the motor mounts, how do I event figure what directions to move the motor? I have seen reference to .003 as a tolerance but how is this measured? Is this in a book anywhere such as Don Casey's this old boat? (I haven't bought that yet, but am willing). Any opinions out there? Reassurances? Warnings?

A little history on the shaft reinstall - When I first tried to install the shaft I had clamped the stuffing box onto the shaft log and put the coupler onto the end of the shaft, then pushed the shaft forward, the holes between output and shaft couplers did not line up well. So I removed the stuffing box and let it float free, and removed the shaft coupler from the shaft and bolted it onto the mother. I then slid the shaft forward. It did not go in easily, truth be told I pounded on the propeller hub with a rubber mallet to get it all the way into the coupler. At that poitn it seemed to be aligned and to spin by hand freely and without discernable wobble. But under power not so much, though it fdoes seem to smooth out as the revs are increased and also seems smoother after a couple of rounds of trying the motor in gear.

Thanks for listening.
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Old 04-29-2016, 10:25 PM
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ndutton ndutton is offline
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The strut bearing is rubber and needs lubrication when running on the hard. Have someone under the boat with a water hose to keep it wet while it's turning. A little liquid dish soap will help too.

Depending on how long it ran dry ("also seems smoother after a couple of rounds of trying the motor in gear") you may have caused considerable bearing wear.
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Old 04-29-2016, 10:55 PM
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The new cutless bearing re defines where the engine should be. If you do not move the engine to mate correctly with the engine you will quickly wear the new cutless and be right back where you started. The fact that the couplers did not line up well tells you what the problem was in the first place. It's ok to do the alignment on the hard; just do a check once the boat is in the water. Never run the engine on the hard with the couplers connected; it isn't necessary. There are a number of threads on this subject but we will be glad to talk you thru if you prefer. First thing, disconnect the couplers, pull the shaft aft 1/2", and post us a picture.
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Old 04-30-2016, 06:01 PM
JimF JimF is offline
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seems OK

I did run the motor again today very briefly, things seemed pretty smooth. I also checked for new play at the propeller due to running dry in new cutlass bearing, did not seem to be any. I loosened all the set screws in the coupler (there are 4 in the Moyer split coupler). at that point the shaft was able loose enough to move inside the coupler. I then backed out the 3 bolts that marry the shaft coupler to the output coupler it seemed to line up so I replaced the 3 bolts tightened the set screws and decided to wait until splash time (Late June this year) to do anything.

Thanks for the input and please tune back in in June, I will post an update either way.
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Old 05-01-2016, 10:26 PM
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About that 0.003" tolerance

Quote:
I have seen reference to .003 as a tolerance but how is this measured? Is this in a book anywhere such as Don Casey's this old boat? (I haven't bought that yet, but am willing). Any opinions out there? Reassurances? Warnings?
Two things to consider:
  1. For that tight a tolerance it's important to take floating stuffing box influence and shaft sag from weight out of the equation. The stuffing box is not a bearing but rather a seal. It floats on a flexible hose typically so it cannot be relied upon to position the inboard end of the shaft accurately. Further, shafting is pretty heavy and with a single bearing at the outboard end sag is inevitable. The only way I know to counteract these issues is to disconnect the stuffing box hose from the shaft log and place three tapered shims between the shaft and inboard end of the shaft log to center it. That is, even gap all around. Only then can your ultra precise alignment be done. Of course, it's wet and risky business if done in the water (I wouldn't try it).
  2. Although popular, the 0.003" tolerance is by no means universally accepted. Please read this treatment by David Pascoe, marine surveyor. His qualifications are listed at the end of the essay.

    http://www.yachtsurvey.com/Alignment2.htm
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Last edited by ndutton; 05-01-2016 at 10:39 PM.
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Old 05-02-2016, 12:32 AM
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Mr. Pascoe's comments are much more germane to the power boat crowd than sailboats. Generally sailboats have stiffer hulls, especially full keel boats, and do not suffer much from hull flexing in most cases. He briefly touches on the point that a correctly aligned coupler pair does not necessarily mean a good drive train adjustment. He correctly points out that the cutless is not always true to the center line of the shaft log which in extreme cases can mean wearing at the forward end of the log. However, he omits to mention that the log does allow a certain amount of deviation from center provided no contact is made and the hose connection to the stuffing box can flex to allow the shaft to mate to the engine without excessive lateral pressure which would cause premature wear. I disagree with his notion that alignment is not important and effective. His comments are more applicable to heavy diesel/high power engines that can squash and flex cheap mounts. The metal in rubber mounts (sold on this forum) are more than adequate for our purpose. What is really important for us is making sure the engine is brought to the point where the shaft wants it. The tail wags the dog. If you do this you will have a successful alignment. Often this means you must spend time centering the shaft in the cutless and supporting it inside the boat. A neat trick I have learned is to buy a 1" shower pole at the hardware, really light and very straight. Use it as a dummy centering it in the cutless and moving it forward until you can see plainly where the engine must be to satisfy the requirement of the cutless which is fixed and cannot be adjusted. And the .003" max deviation between the couplers is the standard I have seen applied in every yard I have ever visited.

Last edited by hanleyclifford; 05-02-2016 at 12:34 AM.
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Old 05-02-2016, 03:48 PM
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JimF,
I was all freaked out about shaft alignment when I went thru this process a few years ago.

The two posts from my thread that dealt specifically with the alignment are:

#323 of the "Indigo" thread
..and..
& #324 .

Now, you don't have to deal with the other 373 useless posts!

I remember referring to both Don Casey's & Nigel Calder's books. I can't remember which was more helpful, but a fresh brain worked the best. Think about the mechanics of what each motor mount does to the alignment, and it should become less cumbersome. Someone reminded me that the aft motor mounts are 'gross' adjustments, and the forwards mounts are 'fine' adjustments due to the pivot points of the mounts related to the shaft's connection to the motor..That was the biggest mental 'help' for me.
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Old 06-23-2016, 09:04 AM
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Final update

Banshee was launched two days ago in Maine. I was not going to be able to be there (I am in Conn.) so even though I try to do all my own work on the boat, I had asked the yard to check the motor/shaft alignment after launching, and I got a call Tuesday evening from their mechanic, who reported unacceptable vibration, and after checking thought the output flange and shaft coupler flange were not tight or aligned. He was of the opinion that I had perhaps damaged the output flange in the process of cutting off the shaft coupler. He worked on it the nexst day - yesterday and called me at 10:30 AM with the great news that he was able to tighten everything up, and made a fairly large adjustment to the motor position and then test drove the boat around the harbor. He reports the motor running smooth (smooth as silk, his words) and zero vibration from the drive train! I love these Maine mechanics, and if anyone reading this is in the Belfast are, Belmont Boatworks has really upped their customer service, and their mechanic is top notch, not just on my job but several friends of mine have had work done by him. I am going up tonight and hopefully I'll be sailing tomorrow.
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Old 06-23-2016, 07:00 PM
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Nice to hear about a good marine mechanic who seems to know what was needed and kept you informed. We don't hear that very often here.
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Old 06-23-2016, 09:24 PM
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JimF, Great news. I think most of us here like to do our own work, but sometimes circumstances do not allow it. Sounds like you had the right guy in your boat keeping an eye on things and making it right.

Good sailing!!
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