Vibrating shaft at slightly high revs.

[GILow]

Originally Posted by Hoohaa

I am removing the flexible coupling when doing the alignment.

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Ah... right. Well I feel silly, did I miss that note somewhere earlier?

[GILow]

Originally Posted by Hoohaa

I am removing the flexible coupling when doing the alignment.

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And now the penny drops, with a sad hollow sound, in my head.

So, if I am right about the coupling being buggered, then you are possibly getting a great alignment without it, only to have the wobble introduced by a buggered coupling when you put it back. Simple test, does the shaft wobble without the flexible coupling in place?

That's a pretty big IF, and I know I sound kind of fixated on the state of the coupling, but IF I am right about the coupling then it pretty well explains the problem I can see. At least it does to my mind.

[Hoohaa]

Problem is that I cant run the prop without the flexible coupling.
If the coupling slides up ok and looks firm enough, i will give it a go just idling in gear.

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[a64pilot]

You don't need to loosen the bolts, there is enough shaft sticking out of the boat I'm sure so it could slide forward the thickness of the coupling.
Having read the installation instruction of a drive saver, they so do the alignment without the driver saver, then install the drive saver. You want the metal to metal faces to measure from.
What I do is install one bolt with a thin washer between the two faces, then lightly tighten the bolt, this holds a set distance on one side of the faces, the thickness of the washer of course, then you can measure the other sides to see if there is an offset, confident that your standard, the washer thickness won't change.

[Hoohaa]

Thanks 64. I will use the washer idea.
I can't bring the flanges together because of an anode attached to the shaft. That's why i need to loosen and slide the coupling up.
Does any one recognise the engine mounts?
I think I will have to make some spaces

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[Cheechako]

Originally Posted by Hoohaa

Thanks 64. I will use the washer idea.
I can't bring the flanges together because of an anode attached to the shaft. That's why i need to loosen and slide the coupling up.
Does any one recognise the engine mounts?
I think I will have to make some spaces

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Well, if there's a nut under ,as it appears your wrench is on it.. raise it up.

[Hoohaa]

I think the nut is there to keep the bolt tight in the rubber mount. By turning it i think I would be just loosening the bolt in its mount and not adjusting the height.
I have made some Packers. So i will insert one on each side at the front.

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[GILow]

Originally Posted by Hoohaa

I think the nut is there to keep the bolt tight in the rubber mount. By turning it i think I would be just loosening the bolt in its mount and not adjusting the height.
I have made some Packers. So i will insert one on each side at the front.

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That sounds odd. Normally the threaded shaft is vulcanised into the rubber mount. Then the two nuts are moved as a pair up and down the shaft to set the engine mount height. From the photos your setup looks like this to me.


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[GILow]

Edit: just had a look at that second photo and I think something screwy is going on. There appear to be some washers acting as spacers suggesting the lower nut is not moving up the shaft as it should (seized?) or the nut currently there is somehow there to keep the engine mount in one piece while the bearer nut is missing altogether, possibly removed to bring the engine down far enough. Maybe now, as the mounts have aged, they have compressed enough that you can reinstate the missing nut and restore the proper adjustment function of the mount.


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[hpeer]

OK, STUPID question. About that 1" gap. Why not put a bolt in the shaft side of the coupling, extra long so that you can put a nut on each side and thereby precisely adjust the length. adjust it so that is just barely touches the engine coupling face. Rotate the shaft. If it binds or doesn't touch somewhere you have a miss alignment.

Also, if you can slide the shaft even a wee bit you should be able to check that it aligns with all 4 holes in the engine side. Thereby checking vertical and horizontal alignment.

That make any sense to anyone?

[hpeer]

Sorta off topic story, on our small boat I went to check the engine mounts. Oops, they weren't mounted ON the rails (3" or 4" angle iron) they were suspended UNDER the rails. Apparently the rails were too high so rather than adjusting the rails they used a hole saw to make holes big enough for the mounts to slide through, then bolted them sticking up through the holes!

Obviously there wasnt much metal left when they did this and it was pretty impossible to do any kind of real alignment. Still things worked reasonably well.

MD7A Volvo. Had been installed like this for over 30 years. The engine had even been removed, completly rebuilt, and reinstalled in this fashion. Go figure.

I cut out the old rails and mounted (welded in) new ones lower down. A bit too low in fact and I had to add shims to get the final mounting height correct. At least I now have a standard adjustable arrangement. All is good once again.

Just an odd story.

[Hoohaa]

Have justtaken the F Coupling out again. Here are some pics of it so you can judge for yourselfs.note the rough edges are outside everything that makes contact.
Also. Its very hard material so i don't think it does allot of flexing.
I will loosen the coupling and bring the plates together so i can check them properly with a feeler gauge. Also added a pic of the spaces I will be using on the mounts.

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[GILow]

Yep, that coupling is fooked. I'd toss it to my onboard spares and buy one I could trust.

Also I would not be stuffing around with spacers. I'd be finding a nut with the correct thread, and putting it UNDER the engine mounting bracket on the threaded shaft. Those a spacers will be a PITA and there's a very real risk of them falling out altogether if the engine mount nut comes loose.

Do it right, do it once.


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[Hoohaa]

I can't see anything wrong with that couplin..
I have checked it with the calipers, no cracks anywhere.
Yes uts fury around the edges but that doesn't distort anything..
I appreciate your input but I can't see anything wrong with it.
It stands true against a straight edge on any point and it's probably only done a max of 200 hours.

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[GILow]

Originally Posted by Hoohaa

I can't see anything wrong with that couplin..
I have checked it with the calipers, no cracks anywhere.
Yes uts fury around the edges but that doesn't distort anything..
I appreciate your input but I can't see anything wrong with it.
It stands true against a straight edge on any point and it's probably only done a max of 200 hours.

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Ok. It's your boat, not mine. :^)

I'd toss it because I don't know what the heck happened to it to make it like that. If I could find a new one that looked just the same, rough edges, shoulders, apparently missing polymer, then I might be reassured. But I also would not consider myself tooled up enough to test it for trueness. Not just parallel faces, but perfectly centred bolt pattern too.


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