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Discussion Starter · #1 ·
Had a big problem while motor sailing when my port motor stringer collapsed, the surveyor never saw the rot, and the bolts sheared between my prop shaft flange and the transmission flange. We survived the ordeal but my problem, after buying a new prop shaft, motor mounts, cutlass bearing and rebuilding the stringer is that the prop shaft does not come thru the stern tube, and thus thru the stuffing box, in the exact, or even close to, the center. If I can avoid it I would like not to remove the strut. Any suggestions?
 
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I cant see how the strut and sterntube alignment changed UNLESS this event bent the strut






Doing this type of thing for as living allowed me to correct it my boat as in general it is done badly when new

For example .090 movement of the strut will change most motors location 1" :eek:

Some picture's of your issues will help people see what your seeing
 

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It's normal for an uncoupled shaft to 'drop' due to the soft nature of the hose connection and the (usually) extra clearance in the shaft log.

It's also possible that this episode bent the strut? Has it been inspected?

Are you still on the hard? Should probably do the final alignment afloat...
 

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I'm not sure I understand, but it seems you bent the old shaft and that may have bent or twisted the strut?
If so, you must get it all back into alignment or you will have very noisy running gear and a lot of future problems. I've seen yards run a string from the center of the flange out the stern tube and through the strut to check alignment, which might help determine your problem. Also, just to be sure, I'd check that the new shaft is indeed straight.
 

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You got the stringer rebuild wrong. The motor mounts are now at a different height so the motor no longer lines up with your stern tube.

No biggie! Sometimes the mounts are adjustable or if not you need packing pieces.

There are three steps to shaft alignment.

1. Center the shaft in the stern tube. Usually done with the coupling disconnected. The goal is to place the centerline of the shaft as close to the centerline of the stern tube/stern gland as possible. Concentricity is the goal.

2. Adjust the elevation and lateral position of the transmission output coupling flange by adjustment of engine and/or transmission mounts so that its centerline coincides with the shaft centerline and with coupling halves approximately matched for bolting together.

3. Bring the coupling halves together loosely and use a feeler gauge to check parallelism of the mating flange faces. (They must be clean.) Check in the vertical (12 o'clock and 6 o'clock positions) and in athwartship (9 o'clock and 3 o'clock) directions. Make additional adjustments (fine) to engine/transmission mounts as necessary. If significant adjustments are made, separate the flanges and repeat step 2 so that you don't disturb the position of the shaft centerline.

4. When flange faces are parallel within the limits specified by the engine maker, tighten all mounting bolts and check for parallel one more time. If problem found, repeat #3.

5. With all mountings secure and flanges parallel, install and tighten coupling bolts.

This is a lot of work and it should be done when the boat is in the water so that it will assume its normal hull shape. Otherwise you may get to do it again.
WARNING THIS IS A LONG AND TEDIOUS JOB
 

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I just went thru installing a new strut.
This has nothing to do w/ you stringer rebuild. If the shaft doesn't line up w/ your sterntube it's the strut alinement.
When I installed the new strut in the seat of the old one the shaft was too high for the stern tube. When I checked the castings while they were the same the machining made the new strut base thinner than the original. I had to rebed the strut so the shaft was lower. I had to add about 1/4" of glass putty under the strut. Also every boat flexes some on the hard so don't spend a lot of time on alinement til your in the water for about a week.
Jim
 

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Discussion Starter · #7 ·
Thank you, one and all, for your insights & input.
 
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