How to properly align the shaft

[acepi]

I have done it the last time myself, but not sure if it was done right. Witha feeler gauge I tried to get it within .003. So,after you take the first measure, rotate the shaft 90 degrees, do you uncouple the shaft or?... Or do you keep the 4 bolts tight on the transmission, and reposition the engine and realign the mounts?
Anybody with a clear procedure. Thanks

[glenn.225]

From my limited experience, I have only done four. First have good visual check that shaft is straight, bearings are good and no other problems. Mark shaft and transmission flanges so they will go back together the same way. Loosen (1/4”) all four (or more) shaft flange to transmission flange bolts and rotate shaft to see if gap is even when rotating, if not shaft could be bent. Remove bolts and separate flanges a little, rotate again checking for any wobble, gap maybe wider in one location than another. Slide flanges as close as possible and check with feeler gauge, adjust engine mounts to even gap all around to .003” or less rotating occasionally. If there is a larger gap it can take some playing around with mounts to get it to align. When you have it at .003” or less align flange marks, install bolts and tighten down to proper torque. New lock washers are a good idea, if used. And if you are on the hard it will have to be redone when you put her back in the water (hull shape changes).
There are probably better guides but this will get you started.

[Boatyarddog]

Leave the shaft uncoupled the entire time.
Imagine crosshairs on a rifle scope.
The scope site looks like 4 quarters, top, bottom and two sides.
Mark the top, measure down, underneath, and each side, you will notice areas that it's easy to get the feeler gauge in, other areas it's harder, if you use the gauge and slide it along the transmission flange to prop shaft flange seam, you'll find the area that is open.
Be sure your shaft is properly supported if the prop shaft "hangs" unsupported, your measurements will be off.
The front mounts, are your best adjusters, the rear minimal.
Front of the engine moving down moves the rear up , and vice versa.
It's right when you can't get the gauge in any where.
Rotate shaft or trans coupler and recheck in 90 degree increments




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[Wotname]

What the previous two posts said

Plus I like to finish up using 4 feeler gauges (all 1 or 2 thou) in the 4 cardinal positions; they should all have the same "drag" or feel as you pull them out.

[Snowpetrel]

I used the method described here
to align my shaft, this system quickly gave me a total angular misalignment up down and port/stb and also gave me the best orientation for the flanges to minimise the slight face errors. A good tip from this is to use a 10, 15 or 20 thou feeler clamped at the bottom and just measure the top and sides. much easier than fiddling with the smaller feeler gauges. Once you have the vertical misalignment you can easily work out by ratios of the flange size to mount separation and the mount screw pitch to find the number of turns on the mounts to get it perfect. Sideways was harder because of no screws, nudging it one way or another got me to within 2 thou. Updown seems close to 0 thou. Two sets of feeler gauges is handy and I wished I could have found one of those stepped or go nogo feeler gauges rather than the normal type.

[Rustic Charm]

I agree with Snowpetrel, I've only done mine on my boat a few times but over the years I've done many gear box alignments for conveyor belts and other heavy industry things. Use a thicker gauge and get it down. The last time I did my boat donk I got it down to nothing, but I think I fluked it. Defiantly don't have the flange bolts done up and then move the engine as that's just adding to the misalignment.

[acepi]

Thanks everybody for the quick reply. This helps me enormous . As I mentioned I had a rough idea, but now it's clear. As a newbie I finf this forum great .
Thanks again.

[Cadence]

It might pay to start by using a dial indicator to check for shaft run out. If OK use it to check both flanges for warp, not being perpendicular to the shaft. Then proceed getting grey hairs with feeler gauges and motor mounts.

[glenn.225]

Originally Posted by Snowpetrel

I used the method described here

Snowpetel that is a very good guide. I'll put if away for future reference.

[Boatyarddog]

You really don't need to remove the shaft to check for runout unless you encounter problems with a basic alignment, I've done over a hundred. Be sure the coupler is on tight, keyed properly, set screw tightened first, then coupler clamping bolts tight.

It becomes an issues of support when long or large shafts are involved, remember you align the engine to the shaft
Never the shaft to the engine.

.003 is spec. Very difficult to get less.

Consider a vibration dampener in line if you've got a really hard to align set up, even these have limits though.
The mounts are important when it comes to rotational torque, and dynamic alignment, the alignment can change under thrust if the mounts aren't solid enough or tightened down well.



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