Alignment issues

[Loki9]

The new A4 is in, but aligning the motor and the shaft is proving difficult. I had the shaft coupling on the shaft and was attempting to line it up with the output coupling on the motor. I'd bring the two together until they touched at one point and then I'd measure the gap on the opposite side. However, I found that when I rotated the mated pieces, the gap rotated with them. Next, I tried sliding the shaft out of the shaft coupling, and bolting the shaft coupling to the output coupling. The two mated well, with no measurable gap, but now the hole for the shaft wobbles as though it is drilled off-center.

The shaft is not bent. The mating surfaces of the couplers are clean. When I ran the motor on the bench, the output coupler appeared to run true by eye.

Maybe that's not the clearest description, so I took a video. Here I've slid the shaft back so that it is almost out of the shaft coupler. The key is removed and the coupler can rotate without rotating the shaft.

Any ideas what I should check? Thanks guys.

[YOUTUBE]SnYFfGYyfNo[/YOUTUBE]

[ndutton]

One simple test to confirm my conclusion: can you arrange an indicator on the outermost edge of the coupler? A popsicle stick will do as long as it's held in place. Then turn the coupler and observe if the outer edge turns true as determined by a consistent gap between it and the indicator, that is, no noticeable out-of-round difference.

With a successful test, I think the coupler is bored off center and not by a little.

Where did the coupler come from?

[ILikeRust]

You need a new coupler. There's no way you should be able to spin the coupling on the prop shaft like that. It needs to be snug press fit or driven fit.

See the discussion here, and scroll down to MaineSail's post and video.

[Loki9]

You need a new coupler. There's no way you should be able to spin the coupling on the prop shaft like that. It needs to be snug press fit or driven fit.

See the discussion here, and scroll down to MaineSail's post and video.

In the video the shaft is maybe 1/16" into the coupling, probably less, and the shaft has a slight bevel on the end. That's the only way the coupling could turn like that without moving the shaft.

[Loki9]

One simple test to confirm my conclusion: can you arrange an indicator on the outermost edge of the coupler? A popsicle stick will do as long as it's held in place. Then turn the coupler and observe if the outer edge turns true as determined by a consistent gap between it and the indicator, that is, no noticeable out-of-round difference.

With a successful test, I think the coupler is bored off center and not by a little.

Where did the coupler come from?

I'll put an indicator on it and see what we see. This coupling came on the motor when I bought it, complete with the end of the old shaft. See the first photo in this thread.

I do have a second coupling, the one that came with the boat. I can try that one too.

[ndutton]

In that case I'd forget the indicator and try the other coupling. The chances of both being off center are virtually zero. If the other coupling does the same thing (I don't believe it will) you have an output flange or related issue but I'm not thinking that direction.

[edwardc]

I don't know, Neil. My first thought was that the tailshaft was bent. But it's hard to imagine how that could happen.

However, as soon as I looked at that photo of the engine in the bed of the pickup truck, on that slanted cradle, it looked like it was resting on the atached stub of the old shaft! I could easily see how it could get bent by an impact on that stub while lowering the engine onto a hard surface, or bouncing along on a bumpy road.

[ndutton]

Yeah Ed, when I saw the picture I was thinking the same thing but still hoping it was the coupler. The indicator test was intended to determine the condition of the tailshaft and output flange. The same wobble with a different coupler would be conclusive too.

[Loki9]

I don't know, Neil. My first thought was that the tailshaft was bent. But it's hard to imagine how that could happen.

However, as soon as I looked at that photo of the engine in the bed of the pickup truck, on that slanted cradle, it looked like it was resting on the atached stub of the old shaft! I could easily see how it could get bent by an impact on that stub while lowering the engine onto a hard surface, or bouncing along on a bumpy road.

Look again, the stub of the shaft in that photo is not resting on the bed, it's a good 6" above the bed. And during transport the motor could not move, it was strapped down tightly. Of course, how the tailshaft got bent is of no importance, rather the fact that it does appear to be bent is what concerns me.

I put an indicator on the face of the output coupling just outside the bolt holes and measured about 0.025" total run out. Not good. Then I tried indicating on the end of the tailshaft, and got about 0.015" of run out there.

Looks like I'll need a new tailshaft at a minimum, and might as well get a new output coupling while I'm at it, and shoot, it's only money, throw in a thrust bearing too....

[jpian0923]

Can you get video of your process for measuring?

Also, I've destroyed two tailshafts because the output coupling was not a press fit. When installing the output coupling you do have to make sure it seats properly against the spacer and stop ring on the tailshaft. If that didn't happen, that could be your out-of-round reason.

[lat 64]

One simple test to confirm my conclusion: can you arrange an indicator on the outermost edge of the coupler? A popsicle stick will do as long as it's held in place. Then turn the coupler and observe if the outer edge turns true as determined by a consistent gap between it and the indicator, that is, no noticeable out-of-round difference.

With a successful test, I think the coupler is bored off center and not by a little.

Where did the coupler come from?

This is where I would put my efforts. In the coupling, the shaft bore must be coencentric with the bolt pattern but not necessarily the outer edge of the flange unless they were turned on the same index.
You can check this by chucking it in a lathe or large drill press and using a dial indicator. The dashhed line I drew is the theoetical circle described by the bolt pattern. This should not be off-center by even a tiny bit. Not sure how to check that one though. Perhaps a machinist can set it up?

R

[Loki9]

Can you get video of your process for measuring?

Also, I've destroyed two tailshafts because the output coupling was not a press fit. When installing the output coupling you do have to make sure it seats properly against the spacer and stop ring on the tailshaft. If that didn't happen, that could be your out-of-round reason.

Video was inconvenient, but here's a photo of how I measured the run out.



0.025" of run out is a lot. I made the same measurement on the another A4 and it was less than 0.002".

[edwardc]

0.025" of run out is a lot. I made the same measurement on the another A4 and it was less than 0.002".

Agreed. Its too much. Looks like your choices for a cause are:

A. The flange on the coupler is bent
B. The hole on the coupler is worn, alowing it to be clamped on at an angle.
C. The tailshaft itself is bent
D. Thrust bearing is damaged (???)

A & B are the more desireable cases, as you don't have to pull the tailshaft.
Any chance you could pull off the coupler and check the lateral runout of the tailshaft by itself? This should tell you more about where you stand.

[jpian0923]

I would like to see the tailshaft measured with the coupling off also.

Does the gap that the arrow is pointing to change as you spin it?

In the video I don't see the cross shaft moving/wobbling. That makes me think tailshaft is straight, at least up to that point.

[Loki9]

Agreed. Its too much. Looks like your choices for a cause are:

A. The flange on the coupler is bent
B. The hole on the coupler is worn, alowing it to be clamped on at an angle.
C . The tailshaft itself is bent
D. Thrust bearing is damaged (???)

A & B are the more desireable cases, as you don't have to pull the tailshaft.
Any chance you could pull off the coupler and check the lateral runout of the tailshaft by itself? This shold tell you more about where you stand.

Unfortunately, when you pull the coupling, the tailshaft now has no support at the rear and just flops around, so I can't check it with the indicator. It's the coupling that rides on the bearing.

Having inspected the parts, I think B is less likely. A is possible, as is D. I don't want it to be C, so I am ignoring that possibility for now, and I ordered a new coupling and a new bearing. My money is on D.