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Old 15-03-2010, 20:45   #1
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Strut, Shaft, Shaft Log, Engine Alignment

It has been suggested by the boat yard that the propulsion system on my 20 year old boat be realigned. This recommendation is based on what you can see in the following pair of pictures:
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You can see that the shaft is below and to the left of center.

The cutlass bearing was replaced two years ago. At the time the pictures were taken last week the cutlass bearing allowed the propeller shaft to move a fraction of an inch and it was worn asymmetrically when looked at end on.

When under way there is no vibration or unexpected noise.

The yard says let's decouple the shaft from the transmission, get the strut and shaft realigned so that the shaft is more centered in the tube where it exits from the hull, then go back and align the engine to the shaft.

The question is, should I go to this expense or just leave well enough alone.

I am looking forward to hearing your opinions.

Kestrelbuck
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Old 15-03-2010, 21:05   #2
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Quote:
The question is, should I go to this expense or just leave well enough alone.
When done right the shaft alignment of .003 inches will sound and feel great. If you can see the alignment is off then it is so far off the cutlass bearing is probably shot already. This is not well enough by a long shot. Not everyone that claims to be able to do alignments can. Some decent folks can do .007 inches and that would be spec for most situations. A little better will work better too. It's about vibration. Less is better and a lot less even more so.
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Old 16-03-2010, 03:17   #3
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Quote:
Originally Posted by KestrelBuck View Post

The yard says let's decouple the shaft from the transmission, get the strut and shaft realigned so that the shaft is more centered in the tube where it exits from the hull, then go back and align the engine to the shaft.

The question is, should I go to this expense or just leave well enough alone.

Kestrelbuck
Unfortunately, the alignment/cutlass/ etc NOT well. best follow the yard's advice
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Old 16-03-2010, 05:25   #4
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Im by no means an expert, but I did just go though the same thing. And every where I read how about alingning the shaft said the boat had to be in the water for a few days so that the hull was not distored by the post jacks. I did align mine after replacening the strut, cutlass and shaft in the yard. After putting the boat in the water I checked the alinment a few weeks later, found it visably off and readjusted. Been ok since.
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Old 16-03-2010, 09:24   #5
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Change the Cutlass bearing in the strut.

Check alignment after boat has been in water a couple of days.

Many times I have seen the shaft a little off center as it exits boat....this is not unusual.

Btw why is your shaft so "red"? You shouldn't be painting it with copper based antifouling...or so I have heard.
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Old 16-03-2010, 09:36   #6
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I had the same problem, except I had horrible rattling noises from the shaft banging on the tube. We laser alligned a new shaft which required removing and shimming the strut, moving the engine.

Still have a rattle about 2400 engine rpm. My next step is to remove dripless packing and return to packing gland, hoping that will constrain shaft.
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Old 16-03-2010, 10:32   #7
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The boat being in the water may help it flex to a better situation but I have a feeling it's still going to be way off. Probably not a bad idea to do a realignment while the boat is out of the water, then perform the fine adjustments when the boat is back in the water.
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Old 16-03-2010, 11:14   #8
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When we did this, I checked the jack stands and there was no "weight " on them. They were tight, and held the boat vertical, but the keel on blocks held all the weight. Blocks were well forward of shaft and strut. My boat is '79 solid glass Cherubini design. Don't think there was much hull flex. None the less when I disconnect to remove dripless and install old style packing gland, i will realign.
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Old 16-03-2010, 13:36   #9
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When we did this, I checked the jack stands and there was no "weight " on them. They were tight, and held the boat vertical, but the keel on blocks held all the weight. Blocks were well forward of shaft and strut. My boat is '79 solid glass Cherubini design. Don't think there was much hull flex. None the less when I disconnect to remove dripless and install old style packing gland, i will realign.
I think the hull will still flex since the keel is not supporting the weight of the boat while in the water.
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Old 08-04-2010, 07:46   #10
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If you are using rubber bearings I believe the rubber will flex more than the hull under the weight and leverage of prop and shaft. So the shaft is unlikely to be centered and if the bearing is not at the balancing point it won't be straight either. As soon as the shaft runs up on the water film it will move, add thrust and the shaft will be bending between supports, it's a pretty crude system and although you can get very accurate static alignment the whole thing flexes and bends in use so it won't be aligned for much of the time. This is assuming you are running a shaft in rubber bearings and taking the thrust on the rubber engine mounts.
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Old 08-04-2010, 14:01   #11
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Thanks for your thoughtful responses. The final decision was to have the yard put everything back in line.
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Old 02-04-2011, 15:32   #12
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ZF10M Problem

The 2 year warranty ended last fall and the Transmission failed a few months later. (Murphy's law)? Only 600 hours on a new enginge and transmission.

The tranny will not go into forward but goes into reverse fine.

Checked and adjusted cable/linkage. It is fine.

Changed fluid twice since I found it an unusual shade of red. (Mauve I would say)

If you rev the RPM's and then idle down it will drop into fwd after a second or two.

When engine returns to idle the tranny will go into a false neutral.

Anyone else see this before? Any ideas on what is wrong? Clutch disks bad?


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Old 02-04-2011, 18:24   #13
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Re: ZF10M Problem

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Originally Posted by bmasson View Post
The 2 year warranty ended last fall and the Transmission failed a few months later. (Murphy's law)? Only 600 hours on a new enginge and transmission.

The tranny will not go into forward but goes into reverse fine.

Checked and adjusted cable/linkage. It is fine.

Changed fluid twice since I found it an unusual shade of red. (Mauve I would say)

If you rev the RPM's and then idle down it will drop into fwd after a second or two.

When engine returns to idle the tranny will go into a false neutral.

Anyone else see this before? Any ideas on what is wrong? Clutch disks bad?


Bert Masson
Norfolk, VA
The color of the fluid seems to suggest coolant getting into the transmission fluid. Do you have a transmission oil cooler?
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Old 02-04-2011, 19:09   #14
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Re: Strut, Shaft, Shaft Log, Engine Alignment

Coolant or water............
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Old 02-04-2011, 21:31   #15
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Re: Strut, Shaft, Shaft Log, Engine Alignment

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Coolant or water............
Should be coolant if it is fresh water cooled.
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