shaft alignment after transmission repair

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Sep 7, 2021
Vessel Name
Fleur de Lis
Vessel Make
1979 California Marshal 42
My 1973 California Trawler (42LRC) had a rear shaft leak on the port velvet drive. The mechanic stated that the entire transmission would have to be replaced/rebuilt. 6K dollars later he stated that the shaft had to be aligned and the motor was adjusted to bring the rear up almost 8 inches and over 2. When the transmission was removed, they pulled the shaft back away from the transmission and left it hanging there without support for 2 months. A couple of questions:
1) was the price for the repair a little excessive?
2) is it standard practice to not support the shaft with the transmission out of the boat?
3) would lack of support cause the shaft to dip in the rear (the prop end) because of weight/pivot point and the thus need the adjustment?
The boat ran fine prior to the leak.

Thank you in advance for your responses.
The price for the rebuild may be a bit high but not out of the ball park.

As to supporting the shaft it would depend on the particular shaft and how it is supported by the shaft log and cutlass bearings.

The engine should be realigned after this work. Not sure what you mean about 8” move.
Normally after any work that moves anything in the propulsion line requires checking the alignment. But it should be close to its' former position.
If you didn't have vibration problems before the transmission work, moving the tail 8" up and 2" over is a huge move. I'd have someone responsible check the alignment before traveling very far with the boat. And look and listen for vibration.
I've installed dozens of engines or transmissions after rebuild. If there were no problems before the rebuild a big move was 1/8". And I align closer than most standards.
Was the trans part of the mounting system of the engine, or engine support on the block w trans hanging on ? If trans not part of mounting it should be darn close on replacement.
Was the final alignment done in the water or with the boat on dry land? Some boats flex significantly, more so if blocked with the flex out of the water. Always a good idea to check alignment after major changes, once it's back in the water. This is a simple matter of loosening coupling bolts between engine and transmission, and then checking with a feeler gauge.

First - Shaft alignment should always be done with the boat in the water - And in the water for at least a week after being on the hard. Second - 8" and 2"? I think there was a miscommunication, or they had unbolted the engine mounts and moved the engine when the transmission was removed. Otherwise a shaft alignment looks more like .008 and .002 - LOL!
The measurements depend on the coupler face size. For example if the coupler is 6” then the alignment should be within .006” all around the coupler. .001 per inch of coupler face.
If the engine actually had to be moved 8" x 2" then something is very wrong with the reassembled engine/gear. Perhaps incorrectly installed mount brackets as has been suggested? Or perhaps the gear was swapped for a different model/style gear, and not a rebuild of the original? Or major structural movement in the boat because it's rotted to the core and about to fall apart, which seems very unlikely. 8" x 2" is an enormous movement.

Or, as stated earlier, it's just a communications issue and the movement was in thousandths of an inch, not whole inches?
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Something’s rotten in Denmark!
I don’t think you got the same transmission back from the shop, 8”lift is not reasonable, and if the removal job had been done correctly, no realignment would have been required, provided that it was in alignment previously.
That's my thought as well. Providing the same or like transmission was reinstalled, no realignment should be necessary if the alignment was good to begin with. The recommendation to check alignment after such work is because it's a convenient time to do it since you're in there and have things taken apart. Alignment can change slightly over time as things wear and settle so it does need checking periodically. The only way it could be out 8" is if a completely different model trans was installed. .008" is reasonable though, the engine mounts could easily settle that much over several years.
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