shaft alignment after transmission repair

[RMK818]

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.

 

[Comodave]

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.

 

[Lepke]

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.

 

[SIBERNUT]

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.

 

[O C Diver]

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.

Ted

 

[sealandsky]

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!

 

[Comodave]

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.

 

[twistedtree]

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?

 

[kapnd]

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.

 

[jgwinks]

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.

 

[Steve DAntonio]

When ever a shaft coupling is separated from a gear coupling, the alignment should be checked.

However, 8", in the world of alignment, is massive, how was this determination made? That seems nearly impossible.

If that was the cost of a complete gear rebuild, it's not unreasonable, but was that necessary for just a seal leak? How many hours on it.

A gross misalignment could cause a transmission output shaft seal to leak.

Leaving the shaft unsupported would not cause it to take on a permanent "set", that's not an issue.

Typically, because it is constant rather than eccentric, misalignment does not cause vibration.

More here The Ins and Outs of Engine and Shaft Alignment Part I | Steve D'Antonio Marine Consulting

 

[liquidsands]

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.

I have changed numerous engines and transmissions both diesel and gas. I never do anything to support the propshaft if it still has support by the stuffing box within a couple feet of the coupler. The weight of the shaft is counterbalanced and held by the cutlass bearing in the rear and the stuffing box in the front. What's left to support? If the shaft dipped in the rear due to the shaft not being supported for two months you have lots bigger problems than an adjustment. The cutlass bearing only has up to an extreme max of 1/8" play preferably 1/16" it couldn't "drop" 8 inches. I think you must have misunderstood what they were saying. If the powerplant position was too far "back" leaving the prop too close to the rudder I could better understand, but how did it work so long in that position without problems? It is possible that a improperly adjusted alignment of the shaft could have been the cause of the rear seal going out in the rear of the transmission. I would try to clarify with them what they did and specifically why. Then you could possibly make sense of it all.
As far as the cost of the repair 6K... if gears and cast parts were replaced as well as a full rebuild I could see it running into that much. I worked for years as an aircraft mechanic, auto mechanic for 5 years and as an engineer on diesel boats in Alaska. The labor to remove the trans, rebuild it and replacing bushings, bearings and worn gears fluids and reinstall with shaft re-alignment, seems a bit high but not seriously excessive at todays labor rates. I would be curious what their explanation is if you care to let me know. Hope all goes well for you with it from now on,.,.,

 

[liquidsands]

Also ANY TIME the shaft gets separated from the transmission and the trans gets moved you need an alignment to make sure the same problem isn't going to occur again.

 

[RMK818]

I have changed numerous engines and transmissions both diesel and gas. I never do anything to support the propshaft if it still has support by the stuffing box within a couple feet of the coupler. The weight of the shaft is counterbalanced and held by the cutlass bearing in the rear and the stuffing box in the front. What's left to support? If the shaft dipped in the rear due to the shaft not being supported for two months you have lots bigger problems than an adjustment. The cutlass bearing only has up to an extreme max of 1/8" play preferably 1/16" it couldn't "drop" 8 inches. I think you must have misunderstood what they were saying. If the powerplant position was too far "back" leaving the prop too close to the rudder I could better understand, but how did it work so long in that position without problems? It is possible that a improperly adjusted alignment of the shaft could have been the cause of the rear seal going out in the rear of the transmission. I would try to clarify with them what they did and specifically why. Then you could possibly make sense of it all.
As far as the cost of the repair 6K... if gears and cast parts were replaced as well as a full rebuild I could see it running into that much. I worked for years as an aircraft mechanic, auto mechanic for 5 years and as an engineer on diesel boats in Alaska. The labor to remove the trans, rebuild it and replacing bushings, bearings and worn gears fluids and reinstall with shaft re-alignment, seems a bit high but not seriously excessive at todays labor rates. I would be curious what their explanation is if you care to let me know. Hope all goes well for you with it from now on,.,.,

Thanks for the great information. I talked to the actual person who rebuilt the transmission. He stated all the clutches and gears looked good. He did not replace any cast parts, just put in new clutches. After the install was complete, the repair still leaked. In fact when I started the motor, the boat went forward (fortunately boat was tied very well to the dock). The boat would either go into forward or reverse. No Neutral. I ended up externally looking at the repair work. Shifting cable was installed wrong (I ended up correcting that) and the neutral safety switch was wired backwards allowing the boat to start in gear. I only figured that out by tracing the wires and using a multimeter to double check continuity. The Mechanics finally finished up the job yesterday. They had to retighten the locking nut and replace the RTV sealant around the spline (fluid was leaking near the prop coupling) and also had to return the shaft alignment to (near) it's original position. The "8 inches" came from the mechanics who did the work. It was more like 3 to 4 inches raised in the front of the engine (based on how high the oil pan sat above my drip pans (before and after). The transmission tech (not the mechanics), did tell me the shaft seal was hard as a rock and the reason for the original leak. He also stated the seal can be replaced without pulling the transmission out. Lessons Learned (just a very expensive lesson). This whole ordeal started in February, and now the boat is operational (4 months later). At least I think it is, I was not there when they tested the transmission today so I will see if it is really fixed the next time I get out to my boat.

 

[RMK818]

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.

The transmission is part of the engine mounting system.

 

[RMK818]

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.

Thank you Lepke. I agree that it was excessive. It was and additional rework had to be done to include lowering the motor back to it's near original position.

 

[RMK818]

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?

Twistedtree, The motor was lifted about 4 inches (measured from the oil pan bottom -before and after). The mechanics had to come back because the leak continued. They brought the technician that rebuilt the transmission, and he stated the alignment needs to be redone and the mechanics brought the engine back to it's near original position. I hate questioning people who are suppose to be professionals in their trade.

 

[RMK818]

When ever a shaft coupling is separated from a gear coupling, the alignment should be checked.

However, 8", in the world of alignment, is massive, how was this determination made? That seems nearly impossible.

If that was the cost of a complete gear rebuild, it's not unreasonable, but was that necessary for just a seal leak? How many hours on it.

A gross misalignment could cause a transmission output shaft seal to leak.

Leaving the shaft unsupported would not cause it to take on a permanent "set", that's not an issue.

Typically, because it is constant rather than eccentric, misalignment does not cause vibration.

More here The Ins and Outs of Engine and Shaft Alignment Part I | Steve D'Antonio Marine Consulting

Thanks Steve. So the repair was 1100 for transmission rebuild, and 5200 for labor (remove and install) 16 hours with 2 mechanics. The repair resulted in my boat being in worse shape than when I started. Several things needed to be fixed that should not have been necessary. Safety Neutral switch wired wrong, transmission still leaked, and the boat would not go into neutral. Had to correct the wiring on the switch and correct the shifting cable that was pushing the transmission shifting lever into forward even though the shifter was in neutral position. They did come back to readdress the leak bringing the Transmission Tech with them. Lock nut was not tightened enough and the RTV around the spline was not set when they filled the transmission with fluid. 4 months later the boat is supposedly ready to take out.

 

[RMK818]

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.

Ted

Ted, the alignment was done in the water. The engine remained on blocks while the transmission was out. Long story short, the original repair and to be fixed again, the transmission still leaked after the repair. After correcting the rear seal again (this time not removing the transmission and done by the Transmission Tech), the realigned the shaft putting it back to it's near beginning position.

 

[liquidsands]

Thanks for the great information. I talked to the actual person who rebuilt the transmission. He stated all the clutches and gears looked good. He did not replace any cast parts, just put in new clutches. After the install was complete, the repair still leaked. In fact when I started the motor, the boat went forward (fortunately boat was tied very well to the dock). The boat would either go into forward or reverse. No Neutral. I ended up externally looking at the repair work. Shifting cable was installed wrong (I ended up correcting that) and the neutral safety switch was wired backwards allowing the boat to start in gear. I only figured that out by tracing the wires and using a multimeter to double check continuity. The Mechanics finally finished up the job yesterday. They had to retighten the locking nut and replace the RTV sealant around the spline (fluid was leaking near the prop coupling) and also had to return the shaft alignment to (near) it's original position. The "8 inches" came from the mechanics who did the work. It was more like 3 to 4 inches raised in the front of the engine (based on how high the oil pan sat above my drip pans (before and after). The transmission tech (not the mechanics), did tell me the shaft seal was hard as a rock and the reason for the original leak. He also stated the seal can be replaced without pulling the transmission out. Lessons Learned (just a very expensive lesson). This whole ordeal started in February, and now the boat is operational (4 months later). At least I think it is, I was not there when they tested the transmission today so I will see if it is really fixed the next time I get out to my boat.

Sounds just like what I expected in regard to the shaft seal. They get hard and crack, especially if the shaft alignment is not perfect. Also raising the front of the 3 inches might only move the angle of the coupler a degree or two. Reasonable. My only other worry for you might be in the angle of the engine. If the front end of the motor is quite high you might be considering the possibility of a future rear oil seal leak on the engine. I had a 6.2 GM diesel that had a rope seal rear oil seal and it was a chronic problem for me. Finally for the marine versions they same up with a redesigned 2 piece oil seal that could be installed in many cases without removing the engine from the boat. I would advise that you keep a couple oil absorbing pads in the bilge below the engine rear as a precaution until you see how your engine will respond to the new increase in angle. Since they are white or light in color you can see right off if you have any issue starting. And yes the rear seal of the VD is easily changeable if you have room enough to slide your propshaft back a few inches. If not, the rear motor mounts can be unbolted and the motor jacked up enough to get access. If that happens them you have to have alignment checked again, but its better than having to remove the trans... Best wishes for the season

 

[Steve DAntonio]

Thanks Steve. So the repair was 1100 for transmission rebuild, and 5200 for labor (remove and install) 16 hours with 2 mechanics. The repair resulted in my boat being in worse shape than when I started. Several things needed to be fixed that should not have been necessary. Safety Neutral switch wired wrong, transmission still leaked, and the boat would not go into neutral. Had to correct the wiring on the switch and correct the shifting cable that was pushing the transmission shifting lever into forward even though the shifter was in neutral position. They did come back to readdress the leak bringing the Transmission Tech with them. Lock nut was not tightened enough and the RTV around the spline was not set when they filled the transmission with fluid. 4 months later the boat is supposedly ready to take out.

I hate to hear stories of incompetency like this, it reflects so very poorly on my industry.

Once again, and for any others faced with alignment work, this is not a black art, it's scientific and basic engineering, however, if a tech hasn't been trained how to do this, then it's almost impossible to do it correctly. https://stevedmarineconsulting.com/wp-content/uploads/2021/04/TaskSheet190-EngineAlignment-05.pdf