Help with procedures prop shaft alignment

[Cocoa Beach Sailor]

So, my current situation is that my boat is on the hard, after withdrawing the propeller shaft I found that the strut was installed so incorrectly that it was virtually impossible to get the shaft back into the transom hole. The stern tube had rotted into bits of decomposed bronze. So I have purchased new motor mounts, a new Cutlass bearing, new stern tube and I will loosen/remove the strut for the shaft.
My plan of action is as follows and I welcome any commentary, even if it has to do with alien abductions and trans medium craft. After installing the new motor mounts, I will run the motor for a bit throttling it this way and that and then let the motor sit for a couple days while I do other projects. Then I will put the shaft into the coupler and move the engine about with the mount Adjusters such that the shaft is centered in the stern hole. I will note the amount of play at the end of the shaft with the propeller removed and I will work on centering the shaft in that amount of movement at its end . I will support the shaft in some fashion or another in the center of its movement . Then I will install the stern tube, making sure that it is equidistant from the shaft with a spacer and I will also install the strut, using thickened epoxy to get a proper set such that, with the new Cutlass bearing, the strut will be centered on the shaft which will be centered in the stern tube which will be bolted up to the transmission. I will be installing a Volvo lip seal and after I get all of these things fitted I will install an R&D flexible drive shaft coupler. After I splash the boat I will make some attempt at measuring the alignment but from my understanding, a beefy hull and a well-centered drive shaft should not vary that much from the difference in Hull flexion from being on the land versus on the water. In the end I will have new motor mounts, new Cutlass bearing, new Stern tube and new prop shaft seal, warp drive, photon torpedoes and retractable landing gear. All laurels, darts, and conspiracy theories are welcome.

 

[Ralph Johnstone]

After I splash the boat I will make some attempt at measuring the alignment but from my understanding, a beefy hull and a well-centered drive shaft should not vary that much from the difference in Hull flexion from being on the land versus on the water.

From what you describe, I think you are in for a full blown alignment. Biiiiiiiiiiiiiiiiig deal. Just a lot of cursing, swearing, and Klingon curses. Learn how to align a prop shaft correctly with the attachment below :

 

[heritage]

If it is like my H27, the stern tube is the only part of the assembly that only has one spot that it can be located. I would fit it first and then slide the prop shaft in with a spacer that will keep it centered in the stern tube. Hopefully the shaft will come close to the center of the engine coupler and in an position that works with the placement of the cutlass bearing strut.

 

[Don S/V ILLusion]

. After I splash the boat I will make some attempt at measuring the alignment but from my understanding, a beefy hull and a well-centered drive shaft should not vary that much from the difference in Hull flexion from being on the land versus on the water.

my experience is that all hulls flex, some more so than others, so consider yourself lucky if you can avoid another alignment after it sits in the water for a while.

 

[Cocoa Beach Sailor]

From what you describe, I think you are in for a full blown alignment. Biiiiiiiiiiiiiiiiig deal. Just a lot of cursing, swearing, and Klingon curses. Learn how to align a prop shaft correctly with the attachment below :

Thank you for the informative link . I understand that it is rather important. However, if the shaft is bolted up to the transmission, free of any encumbrances, and then the stern tube and prop shaft strut are installed, centered on the shaft, I should be starting out with perfect alignment, minus whatever Machining run out there is on the face of the coupler. I am hoping to take the shaft and coupler, which should have been mated properly upon their installation, to a machine shop to have them evaluated and machined. When one aligns an engine, in truth they are aligning it to the prop shaft strut. I will be doing the reverse, which is mounting/aligning the prop shaft strut to the engine.

 

[Tally Ho]

Thank you for the informative link . I understand that it is rather important. However, if the shaft is bolted up to the transmission, free of any encumbrances, and then the stern tube and prop shaft strut are installed, centered on the shaft, I should be starting out with perfect alignment, minus whatever Machining run out there is on the face of the coupler. I am hoping to take the shaft and coupler, which should have been mated properly upon their installation, to a machine shop to have them evaluated and machined. When one aligns an engine, in truth they are aligning it to the prop shaft strut. I will be doing the reverse, which is mounting/aligning the prop shaft strut to the engine.

I am not sure that you have ways to adjust much after of the engine. On most boats, the strut and cutlass bearing, and the stern tube/shaft log are not adjustable. You move the engine up and down as well as change it’s angle, to get the shaft to line up properly in the strut and stern tube.

When I replaced the shaft, coupling and stuffing box hose a few years ago, I slid the shaft through the strut (without the cutlass bearing in place), then into the stern tube opening. This was hard because I did not remove my rudder, so I had to pull in the shaft a bit to get it started in the opening. Then I slid it in until it cleared the rudder…then I pressed in the cutlass bearing. Then from inside, I centered the shaft in the stern tube and used some sticks or something to keep it centered. Before I put the stuffing box in place, I slid the shaft up to the transmission flange and made sure. It was centered. Satisfied with that, I removed the sticks holding the shaft in the stern tube, installed the stuffing box hose and then the stuffing box. Finally, I pushed the new coupling on the shaft and pushed it up to the transmission flange. I bolted the flange and coupling, and carefully rotated. The shaft to see how tight it fit against the output flange. Looking good, I used a feeler gauge to see if the “gap” was consistent all around the coupling. In my case, I did not need to make any engine adjustments.

Remember that once you put the boat back in the water, the hull will probably change a little, so a small adjustment maybe required after the boat is splashed.

I don’t know if tis of any value, but I made some videos of my project….this is the last in the series of the shaft replacement…I didn’t capture every moment of the project, and I don’t have any video showing the use of the feebler gauge, ut maybe it helps in some way.

A year later, I removed the coupling and replaced the stuffing box with a Volvo dripless seal, and had to go through some of the steps again…

Good luck.

Greg

 

[Ralph Johnstone]

However, if the shaft is bolted up to the transmission, free of any encumbrances, and then the stern tube and prop shaft strut are installed, centered on the shaft, I should be starting out with perfect alignment,

You would be far more correct to say the Earth is at the centre of the Solar System.

So I have purchased new motor mounts

Replacing the motor mounts alone will guarantee that the angular alignment is out by at least 0.050" to 0.100". You will be aligning your engine to a maximum error of 0.001"/inch of coupling flange diameter in inches. There is no way you can install the engine to replicate its original location. AND there is no reason to believe your engine is currently aligned unless it has been recently aligned.

Thank you for the informative link . I understand that it is rather important.

Far more important than that. Unless the alignment is done with some sort of system, it's out of the question.

I hope you're not thinking of "vertical and horizontal alignment" only. This can be done by fingertip feel if your comfortable with alignments. If not, use a straight edge. Unfortunately, many couplings are not exactly the same diameter so it's back to the fingertip method. They are not the important measurements just because of your rubber mounts. Lean on your engine and see how much the vertical and horizontal alignments change. No stress on the shaft so no foul.

ANGULAR alignment is the one to be concerned with and it's a bit of a bugger (time consuming) to get correct.

Please read (and understand) the alignment theory and instructions offered in the attachment found in post #2. Understand angular alignment before you even get close to your engine.

but I made some videos of my project….this is the last in the series of the shaft replacement

Follow Greg's videos in post #6 as they are excellent in following a procedure. I often suspect he was a movie director in a previous life.