Need shaft alignment

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Oct 25, 2023
City: Half Moon Bay
Join Date: Oct 2023
Posts: 4
Need help shaft alignment
Dear all, my sailboat is equipped with a Ford Lehman 80hp and a Velvet transmission, few months ago I removed the engine for maintenance without removing the shaft. The shaft is mounted on a pillow bearing 2 feet from the coupler, and 4.5 feet from the pillow bearing to the cutless bearing, the coupler is equipped with a drive saver, the shaft is 1.5 in diameter, the coupler, and the drive saver are not new. No matter how much I try I can't get less than 25 mils in the vertical and horizontal, I use 2 dial indicator at 90 degree and the measurement is taken at the end of the shaft where the coupler is attached, the reason for that is the surface on the coupler is rough and the measurement is not consistent. On many YouTube video experts says that the recommended tolerance should not exceed 10 mils. Your help is appreciated
Have you checked that the shaft is actually straight? I would get rid of the Drive Saver since you can’t do a proper engine alignment with one of those in the mix. Spurs made me some spacers to replace the Drive Savers when I removed them on our last boat. As to alignment, it depends on the size of the coupler face. If, for example, the coupler face is 6” diameter then you should have the alignment within 6 thousandths. If it is 4” then 4 thousandths. 10 thousandths is quite a large difference in the alignment.
Is your boat made of wood or fiberglass or other?
Are you hauled or in the water?
Need to perform final fine tune alignment with boat in water as hull can change shape ever so slightly when floating versus on the hard being support by poppits.
By all means, check the condition of the engine/transmission mounts before proceeding! A collapsed mount (or 2) will give you the problem you're experiencing.
Take Drive Saver off, sldie shaft up till it makes with the tranny flange, and then align.

If flange is not smooth you will need to rotate it around till all looks good on feeler gauge.

Motor mounts are a cheap fix, and well worth it.

Go to grandbankschoices, and dig around and find where I changed mine. Took a couple hours by myself.
Shaft alignment

Thank you Comodave for your advise, how you can tell if the shaft is missaligned from being bent?, the boat is in the water and I can't remove the shaft.
Thank you
Hello Mac G, the boat is 46 ft made of fiberglass and it is in the water. Is the material that the boat is made of important?
Boomerang, the transmission is bolted to the engine and have no support, the engine have four motor mount and they are new
Choices, the motor mount are new, I replaced them when I removed the engine. The bot is in the water and it is equipped with a dripless system, I can slide the shaft few inches aft however the coupler that is connected to the shaft seems very sticky after years of service. Any idea how I can remove that part without using brutal force. Thank you
Good morning Dido. Check your shaft by rotating with a stilson wrench. Put a chalk mark or sharpie mark on the coupling and watch it against the gear coupling. If the the shaft coupling goes up, down, or sideways, it's bent.
Hello Mac G, the boat is 46 ft made of fiberglass and it is in the water. Is the material that the boat is made of important?

Wooden boats need to swell up and things can shift.
Some fiberglass boats are thinly made and not very stiff, can flex when hauled.
Aluminum and steel boats tend to be stiffer.
But if you are in the water then it takes that variable out.
You always want to do final alignment when in water.
If you were fully aligned before and you replced the motor mounts, then I would look at that component of your installation.
Are the mounts identical insofar as dimension and adjustment range?
If you need to take the coupler off the shaft and it isn’t a slpil coupler the easiest way I have found is to take a piece if about 3/8” steel plate and drill holes that will line up with the holes in the coupler. Then put a large socket in between the coupler and the steel plate. Put bolts in the holes and tighten them and the socket will press the shaft out of the coupler.
To check the shaft, use the dial indicators. Put one near the bearing so you can see the bearing runout, and put another on the shaft near the coupler. If the indicator near the coupler is showing a bunch more runout you have a problem.
Try to get that drive saver off and out of the way for the time being so you can clean the face of the coupler. Use a nice flat, hard block with some 600 wet and dry paper. Dress it like you would do a clutch surface on a flywheel.
Then use the indicator on the coupler face and check the runout.
While we’re at it, check the runout on the velvet drive output flange. All of these need to be within reason before you can align the engine to the shaft.
I would never try to line up on the drive saver, it can be all over the place. If you can’t get the shaft up to the output flange with the drive saver out, you should get a spacer made up. Patience and attention to detail will get you there.
Dear all, thank you for all the help and advise, since the best way to align the shaft require the removal of the drive saver, do I need also to remove the coupler from the shat?. Would you please take a look at the attached pictures and let me know how I need to proceed. The coupler is split but not all the way, there is 3 Allen key bolts and 2 Square head bolts and 2 pins, it seems too much for a coupler. Also in order to remove the drive saver I have to push the shaft aft about 4 inches, my boat is equipped with a PSS dripless, what precautions I need to take since the boat is in the water.
Thank you for your help.


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First thing is to determine how much you can slide the shaft aft in order to remove the drivesaver. When I did it I ended up cutting some of the bolts on the drivesaver and replaced it with a custom made spacer since there wasn’t enough shaft to slide it forward. If you have room on the shaft to slide it forward so the 2 couplers will come together then you don’t need to remove the coupler. As to the PSS I haven’t had them so I am not going to advise you on them.
That's not a Drive Saver, but as others have said, I would still ditch it, these are simply an excuse to avoid proper alignment, and you can't check alignment with the flexible coupling in place.

The shaft coupling does not need to be removed, however, if you suspect its face is not perpendicular to the shaft, then both the shaft and coupling should go to a marine machine shop for fitting and facing.

More here...


Engine alignment step by step

Motor mounts:

More alignment:
I suspect that coupler has been modified to add the socket head set screws, the square heads were likely original. I can't see how the additional ones would be needed with a split coupler which is fitted with a keyway and pin. Check the diameter of each end of the pin as I would think it is a taper pin and has to be driven out only one way. It will be interesting to see what the machine shop says about that coupler. They aren't expensive so it might make sense to just get a new one properly fitted to the shaft and faced. I don't like the look of that one and since you are going to go to all the effort to pull the shaft and have it trued up why not start with a good coupler and then you know where you are.

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