Shaft alignment question

[John F.]

I posted before that I have a wobble in my port shaft, and JP suggested that I check the shaft alignment. I went down to the boat, and I realized that I don't really know how to check alignment. So, I loosened the six coupling to tranny bolts just a bit. I then stuck a feeler gauge in at 4 different positions (12 o'clock, 3, 6 and 9). Starting at 12 o'clock, I got measurements of 14, 10, 15, and 12. Did I do this right? If not, what do I need to do? The measurements seem really close. Thanks.

[Navatech]

Involving Engine/Shaft Alignment by David Pascoe

Drive System Alignment by David Pascoe

[JP Dalik]

John.


Verify the shaft turns freely even in the water this can be checked. If you can't turn the shaft by hand it's a sign there is an issue.
Give yourself an alignment mark on the transmission side and the prop side an seperate the coupler. If it springs off to one side, that's an issue too

Now pull the shaft and coupler together and check every 90 degrees. The gap needs to be even all around, evening the gap is done by moving the engine mounts ever so slightly until you've achieved an even gap, you don't want zero on one side an .010 on the opposite side

It's tedious but important.

[Harry Babb]

John

Before you starts shifting the engine around its very important to know if the "Shaft Coupling Face" is square with the shaft....if the coupling is not precisely fitted to the shaft you CANNOT achieve a good alignment.

Its very easy to check this.....
Clean the faces of the gear coupling and the shaft coupling by sanding the faces to remove rust and crud that accumulates on the couplings. Then slide the shaft coupling onto the gear coupling so that the male register and the female register (Coupling Boss) are comfortably engaged. Using a feeler gage you can detect where the coupling faces are touching and where the faces are gapped apart. Just for illustration purposes lets pretend that the "Gap" between the faces (no matter how great or small) happens to be located at the 3:00 position. Now hold the Gear coupling stationary and rotate the shaft 180 degrees. If the gap remains at 3:00 then your shaft and coupling are fitted correctly and the coupling face is square with the shaft. On the contrary if the "Gap" follows the shaft rotation then the coupling fitup on the shaft will need to be corrected before proceeding.

Misalignment will cause shaft wobble and vibration......but.....its impossible to get a good alignment if the coupling and shaft fit is not correct.

So what comes first here.....the chicken or the egg! ! !

hb

[John F.]

JP and Harry - Thanks. Without your advice, I'd have no idea what to do. I really appreciate it. Next decent weather day when I have time I'll check this stuff out.

[John F.]

OK. So its not a decent weather day, but its better than its been.

While the boat is out of the water I'd thought I'd pull the shaft and have it, the coupling, and the prop checked but the local shaft/prop guy. He had told me previously to bring it all to him so that he could check everything and get it all straight.

I've loosed the pinch bolts on the coupling (laying on the ice that was under snow when I shoveled out the cockpit). The shaft is sliding out OK. I laid on my back and kick at it the prop moderately with the soles of my work boots and the shaft/prop is sliding out fine.

I've pulled props, but never the shaft on the boat (trying to be clear about which of my shafts I've pulled).

Am I in for any surprises? Will the shaft clear the rudder or do I have to drop that? Its going to be really close. Anything I need to watch out for?

Thanks. Wish it were 40 or 50 or 60 instead of in the 20s.

[Tooeez]

You're a better man than I, Gunga Din: I don't even want to go outside anymore, never mind work on the boat in this weather . . . Anyway, if the shaft doesn't clear the rudder I suggest leaving the rudder right where it is, and dropping the strut instead. Since you have everything apart it would pay to have the cutless bearing checked and replaced if necessary. Disassembling an old rudder assembly can easily turn into a project in itself, the strut is just four bolts.

[John F.]

Didn't clear the rudder, so I dropped the rudder out. I redid that stuff last winter, so the unbolting and dropping took maybe 5 minutes. Digging a hole for the rudder to drop into, and a trench so the shaft could be pulled back took a little longer. The ground is a bit harder this time of year. The coupling, shaft and prop will all go to the prop guy. So at least I'll know that stuff is straight. Totally sucked laying in the snow/ice/mud/gravel doing this though.

[John F.]

It turned out that the shaft was straight and the wheel fine, but that the coupler had too much play in it. New coupler, 4-blade props, and new cutlass bearing (because the old one was about shot) and she ran fine today. Got 3100 rpm+ and 31-32knts WOT. Not bad.

[Pete Fallon]

John F,
Did you check your motor mounts, worn or collapsed mounts will give you a wicked vibration also. Glad you fixed the problem with the misaligned coupling. Make sure the mounts are still in god shape, no collapsed rubber inserts, broken bolts, or engine shifting.
Pete Fallon

[neil]

Pete,very good point we just had engine mounts replaced due to a vibration