Prop/Shaft Shear Failure

[whammond]

Last weekend I was just cruising along pulling a friend behind my boat and all the sudden there was a slight jerk and I lost all go-go juice. The engine was still running, just wasn't going anywhere. I discovered the shaft was still rotating, and I thought I had just lost my prop somehow and it had fallen off...if only. After I get the boat out of the water, I discover that my shaft had sheared off right next to the prop. We were skiing in the same cove we have been for 20+ years so I'm assuming that I hit something that was partially submerged?

Anyways, what all am I going to need/do to get this thing back in action? Following that, what all should i go ahead and replace/do since the shaft will be coming out (i.e. cutlass bearing?) I'm assuming i'm going to need a new prop and one of these shaft systems from skidim.

http://www.skidim.com/products.asp?dept=1011

As a forum reference: it seems identical to what happened to NoWake
https://forum.supraboats.com/showthread.php?15849-Shaft-failure-part-Deux&highlight=shaft+failure

Boat Info: '92 Comp. 351W ProBoss. 1.23:1 Tranny.

[whammond]

Pics
http://i.imgur.com/JXzQ1bj.jpg (http://imgur.com/JXzQ1bj)
http://i.imgur.com/7OGg0dk.jpg (http://imgur.com/7OGg0dk)
http://i.imgur.com/HsdUAxe.jpg (http://imgur.com/HsdUAxe)

[yjwrangler95]

Mine did the same exact thing last summer. Mine looked like it has been cracked for quite a while and the torque finally took its toll. I replaced mine with a new shaft from skidim along with new shaft packing and cutlass bearings. The hardest part was getting the nut off the trans coupler, the cotter pin was a pain and I had to grind down a socket to fit in the space, it was pretty tight in there.

[chris young]

Bummer,

I lost my prop to bad fit and no cotter pin at the very end of last year. Since I already knew of 2 (with you and yjwranger that makes 4)shaft failures on similar vintage Supras, I decided to pull the shaft this spring and do a dye penetrant check in hopes that I wouldn't loose my new prop to the same fate that you just experienced. From what I understand, cracks start right at the corner of the keyway, and this may be caused by installing the prop without doing a proper lap fit. So I'm doing a proper lap fit in the shop, the shaft showed no cracks in the dye check and I'll do as close to a perfect alignment with a new coupling that I can muster. If my shaft fails at some point in the future, then we'll have another data point.

I would think the A.R.E is a good way to go, once installed, you should be able to re use your coupling, which, on a straight shaft you aren't supposed to do. I'm also using the new style shaft bushings from Skidim.

Now's your chance to try a new prop, assuming the one you had on there was original. If you contact ACME, tell them what the boat is used for, tranny, and max engine RPM they will recommend a prop for you. A lot of guys here and on the other forums are loving the 541, which I just bought, but I'm on a 1:1 so you would need something else. The tried and true method for getting the coupling off is to get 4 pieces of threaded rod, remove the existing bolts from the coupling, put a socket with an outer diameter smaller than an inch in between the coupling and the transmission, and then re assemble using the threaded rod. Then you simply tighten down the nuts and the coupler will come off the shaft. Now is also the time to replace your shaft log hose, (get the good stuff, your boat can sink if it fails) http://www.marineoutfitters.ca/index.cfm?category=10025|10601&product=23591658&code=BA%2080HO15012

All this stuff is pretty easy, so if you have to pull the shaft anyways, you might as well do it all. If you want a dripless packing, now is the time to upgrade to that as well. I still haven't decided yet.

[yjwrangler95]

I run an ACME 1792 on my 1990 Sunsport 1.23:1 trans w/351. It pulls really well and I did not loose any top end.

[CJD]

Hmmm.

This is making me think I should remove my prop and make sure it's lapped on the shaft properly...

[SquamInboards]

I run an ACME 1792 on my 1990 Sunsport 1.23:1 trans w/351. It pulls really well and I did not loose any top end.

You should put your prop specs and boat info on the "Prop Specs" sticky. That way others can easily find good info on prop choices... any info you can add is helpful, and of course, the more the better! Thanks!

Here's a link to that sticky: https://forum.supraboats.com/showthread.php?15325-Prop-Specs-ONLY

[CornRickey]

Happened to me. My thoughts it was a fatigue fracture. Insurance coveted it as a prop strike. Did the labor myself and they posted for a new drip less seal and bushing

[SquamInboards]

I forgot to add - it has happened to me too, but it was on a friend's 1966 Correct Craft. God only knows how old the shaft was on that. But it broke right behind the transmission coupler, so it saved the prop!

[chris young]

Well, with CornRickey, that makes 5 on this list alone. Which boat did it happen on?

I did my dye check a couple of days ago, it cost me 60 bucks for the kit, I'm doing the lap fit today or tomorrow, I think the extra time and money is worth the peace of mind. The machinist that shot the lapping video I posted also does a dye check on a pair of shafts and shows you what a crack looks like. In there he also says that this is where they all break, caused by a loose prop. http://www.youtube.com/watch?v=8YVUQYpNHZw

BTW, anyone in my neighbourhood who wants to borrow the kit to do their own, shoot me a PM. I'll loan you the prussian blue and valve grinding compound too.