inboard prop shaft alignment

markrsimon said:

For those of you who have gone through this process, did you try to account for the drop of the shaft as it enters the boat? Considering the only thing holding the shaft in-place at present is the brand new cutlass bearing -- the coupler end sits a bit lower than the transmission, yet can easily be lifted up to bolt into the transmission (straight shaft, non v-drives). As I go through the process of checking alignment - should I be concerned with this drop, and perhaps not being aligned properly?

At present, I've lifted the shaft up slightly so I can bolt the coupler to the transmission - finger tight - helping to support the front end of the shaft. I've made a few adjustments and I've still got a slight gap at 8 o-clock that I'm working to correct. Granted, I'll need to do a final check/adjustment once its back in the water - but will this process work, or should I be tackling this differently?

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Bt Doctur said:

You need to center the shaft in the shaft log first. Then adjust the engine bed to match. Then do the alignment. Standard is usually .0001 per inch of coupler diameter.
https://stevedmarineconsulting.com/the-ins-and-outs-of-engine-and-shaft-alignment/

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Strecker25 said:

You’re on the right track. I just did this myself and will also need to do the final alignment after being in the water for 2 weeks.

here’s what I did:
1) Straightened strut and aligned to shaft log, rebed strut with new cutless
2) . I took the old cutless bearing and also a piece of 4” PVC. I cut a slot in the pvc so it would self center when put into the log. I then inserted the old cutless into the pvc and installed the shaft temporarily with no dripless
3) I now had a shaft centered in the log but unsupported by the trans. Installed the shaft coupler to the shaft.
4) since the shaft was where I wanted it - I aligned the engine to the coupler until i could slide the coupler ends together with no resistance. With the shaft held in place it was so much easier to get rough alignment.
5) remove shaft, pull old cutless out of log, install dripless, reinstall shaft, tighten shaft coupler
6) now dial in alignment as much as possible. I have 0 clearance (tight fit) from 2oclock to 7oclock on the mating faces between coupler and trans. There is .005 from 7-2. in other, words it’s close
7) when in the water I will really dial it in shooting for .003 or less. I should only need to drop the front right mount slightly to tighten the gap, but the hull will settle in the water so that could change.

I’ll be following a fantastic document that @techmitch shard that I’m sure he’d send you as well.

bottom line for me was eliminating one variable (shaft movement) simplified the process dramatically.

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techmitch said:

Here ya go; http://www.marinegears.com/pdf/GetInLine.pdf

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markrsimon said:

I like the idea of trying to center the shaft in the log - I’ll have to work on that and see how things line up first, then tackle the measurement process.

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