Scarab29

Not sure if I should Replace the broken shaft myself or send it out... Is there any shimming that will need to be done, is there much involved ? I had a Alpha 1 gen 2 counter rotating apart last year but ended up just replacing the drive.. The alpa didn't seem to hard ..

Mr Gadgets

Scarab,
where did the shaft break? Right at the taper, perhaps. Years ago, that is where they would break because they were a two piece shaft (as I was told). I would replace it with an aftermarket shaft. I perfer the Imco brand.

You can replace the shaft yourself. Gear lash is setup with shims infront of the driven gear and shims under one of the middle bearings. So when you pull the propshaft, all you need to do is get the preload on the bearings correct and you are back in business.
Best way to do that is to mark the case where the tab is bent over. And mark the retainer ring. Unscrew the retainer (special tool needed for that) and install the new propshaft and check the seals on the propshaft bearing carrier. Any water or lube in between the, I would replace them. Depending on hours on the drive and amount of wear on the old shaft, probably a good idea to replace them. More special tools are needed to replace them. Once you get it all back together, there should be NO slop in the shaft. It needs a bit of resistance to turn it. I believe 3-5in/lbs on used bearings is the spec. So if you set the retainer nut back where it was, the preload should be about right. If you feel it is a still loose, you can snug it a bit more. The tabs line up at different spots so you could go a bit tighter to the next tab alignment. The crush ring could be reused, seeing that you are going back to where it was or tighter.
Hope that helps you make your decision on a DIY or take it in. Let me know if you have any questions.

Dick

Scarab29

Yes it broke around the taper just on the inside of the seal, I have oil leaking out... Do you hear of many of these shafts breaking with no other damage to the drive ?

Mr Gadgets

Well back in the day, the cats had problems breaking the shaft at that point. I was told it was a two piece shaft welded at the taper. After market ones are one piece. The 1.25" propshaft is Merc's answer to this problem.
I have not actually worked on any that broke there. I would think unless there is evidence of an impact the internals should be ok. But pulling the propshaft bearing carrier would tell you more.

Dick

Scarab29

I guess we will see when it is apart.. Thanks for the info..

blue thunder

Typically what I do with a crush sleeve is add a .005 shim behind it and then tighten it back to where it was to ensure I get a little preload on the sleeve. If you have an in-lb torque wrench, go to 10-12in-lb rolling resistance total. Thats 5-6 for the prop shaft and 5-6 for the vertical shaft, summed 10-12. I have broken propshafts where you say and just replacing the shaft fixed the problem. Now I pay close attention to how the shaft looks to make sure I don't loose another $500 prop.

Mr Gadgets

In a pinch I will take a beer can opener and open the folds on the crush sleeve a bit.. Then you can bring it right to where you need it and it still holds the shim that the oring seals on, in place.

Scarab29

Thanks for the info, although I think I could have did it myself, I started looking and the seal was ripped so I pulled the lower and had a shop do it... Thanks