Shaft alignment

[eburklo]

2003 Carver 564 with Volvo D12 and ZF311 transmission. When we purchased the boat in 2013 our surveyor recommended shaft alignment. We have not done this as yet now just over 200 hours. I'd like recommendation as to the necessity of having this done. I do not have any vibration issues. The prop were tuned in 2016.
I do see what looks like black like soot or maybe small pieces of rubber under the transmission.
Is there a rubber gear between the engine and the transmission?
Any ideas would be greatly appreciated.

[mjk1040]

I do believe the recommended tolerance between the coupler plates is 3 thousands of an inch at the plates. Some mechanics will go even less.

[SanJuanDreamer]

Its manufacture recommend.
If you don't feel vibration, then it should be a quick check anyway.
If you have Mech do it, they check the tolerances stated above and say its good.
You can do the same. But it should be checked...

[Viper]

What the surveyor is reporting is likely the alignment of the shaft going thru the tube in the hull as seen from under the boat. They like to see it centered as that indicates that the strut is in alignment with the tube. This also helps with the shaft log being square to the shaft and tube. The surveyor would not be able to tell if the shaft to engine alignment was bad unless he uncoupled the shaft coupler from the transmission and took some measurements, or took the boat for a ride and noticed a vibration or the shaft and log wobbling while underway.

Is the black soot under the transmission or the shaft log? Big difference. If it's under the shaft log and you have a face seal type dripless log, your carbon stator is wearing and is likely due to improper alignment or lack of lubrication (water).

If there is rubber or plastic under the transmission output flange, it could be that you have a drive saver and it's wearing. This could be because of alignment or a previous impact caused some damage and the drive saver was ignored in the repair.

Alignments are important and the consequences of a poor alignment really depend on how bad it is and where. Even off a little will cause stress that will eventually get worse and cost money to replace anything from cutlass bearings to transmissions if it's ignored long enough. For what it takes to at least check the shaft to engine alignment while it's in the water, it's a worthwhile exerciser IMO. This will not however correct a bad strut alignment.

[eburklo]

Thanks for the ideas. The soot is under the transmission. I will contact a local Volvo dealer and have them check the shaft alignment.

[Royb]

Hello,

I can say for sure that shaft alignment is extremely important, not only to provide longevity of the strut bearing but will also put strain on the SKF seal bearing on the output drive of the ZF transmission as well as premature bearing wear on the bull gear. Having a shaft out of alignment will eventually cause wear on the shaft at the strut bearing as well which will result in having to weld and re-machine the shaft. The process to align isn’t horrible but will take 2 people for sure and once it’s completed, you should be able to turn the shaft freely with one hand. Although quite technical, should someone require the procedure for aligning the shaft, I would be more than happy to post.

[Royb]

It’s quite important to have the shaft aligned for several reasons. If the running gear is out of alignment it will put stress on the bearing seal (where the shaft connects to the transmission). When this begins to fail you’ll have transmission fluid start leaking, hit the shaft coupling and start spraying all over the place, forcing you to replace the seal. You’ll also have premature wear in the strut bearing which can also begin wearing the shaft as well. I have a Carver 530 Voyager with 675’s and you should be able to turn the shaft by hand, with a properly aligned running gear. 2 experienced technicians can do both in one day and is quite tedious due to the space inside the engine room.

[km1125]

I'm curious how often folks do the shaft realignment procedure? Would you only do it if you noticed a vibration or some other symptoms, or would you do it as a preventative measure every 'x' hours of runtime or 'x' years of ownership?

[Viper]

Because I only get called when there's a problem, it usually only gets done when replacing running gear, major impact, etc. It's good to do though soon after a boat is new to you in hopes of fending off premature strut bearing wear at the very least. This starts you off as a new owner knowing that the running gear is properly aligned then can basically be left alone unless you have an impact or something get's replaced like a transmission. The only other reason I can quickly think of would be loose motor mounts, a new vibration, etc. Had a customer that never had a vibration or impact, then one day on an outing, he started vibrating for no reason (there's always a reason). Turned out his stringer cores were mush and his engines moved.

[Royb]

You should always be able to grab the shaft with two hands and turn it freely. If you can’t, it’ll require adjustment.