Drive shaft pulled out of transmission - 89 Supra Sunsport

[dyost]

So tonight we had finished our wakeboarding and decided to take a quick surf. My buddy gets out to ride, does a platform start and about 5 seconds into the ride I hear the engine wind up. Take it out of gear, look back, and then a 4in diameter and probably 7ft long driftwood stick pops up, chewed up right in the middle. At this point we have no drive, so shut it down and get a tow.

Once we dumped all the ballast on either side of the engine hatch and get a look inside there it's obvious the drive shaft has pulled out of the transmission.

Anyone know how this is connected? It looks like the drive shaft is threaded. Does the driveshaft thread into that bolted joint on the transmission?
How would this need to be repaired? It also seems there was a pretty good leak coming in my prop shaft seal packing (which I had just changed in March this year).

It was 8:15PM when it happened and probably 9 ish when we got back to the dock so I haven't surveyed the damage much at this point. We had 4 kids on the boat 6, 4, 3, 7mo and four adults so I really just wanted to get all the little ones home and wan't worried too much about the boat at that point. Luckily my riding buddy knew the only other boat out in the cove and we called them in for a tow.

I'll try and get some pics tomorrow, but thought I'd at least get the discussion going and see what everyone knew about this.
Thanks,
-dy

[Jetlink]

Pics will help tremendously here as I have seen two different types of couplers on these boats.

[leetudor]

There should be a nut on the end of the shaft and could have a set screw from outside into the nut.


http://cdn.greatlakesskipper.com/media/catalog/product/cache/1/thumbnail/600x/9df78eab33525d08d6e5fb8d27136e95/3/1/3167c03aa97b61cc4e75e85eb1be1638.jpg

[michael hunter]

Like the pic above tapered shaft, key and nut with a carter pin . I would expect the cuppler is shot you should also have the shaft checked . A good time to replace the cutlass bearings.

[tripster]

If the cuppler is bad, some supras have a deep cuppler and some shallow cuppler. Skidim only carries the deeper one. To get the shallow cuppler, buy the deep one take the old and new cuppler to a machine shop and have them turn it down to the same depth of the original cuppler. Machine shop did mine for about thirty dollars and it took them about thirty minutes to do. Worked like a charm.

[michael hunter]

My 89 has the deep one.

[tripster]

crazy. my 89 has the shallow.

[michael hunter]

I was wrong my 92 comp is deep the 89 Sunsport is shallow

[NoWake]

My 91 comp is shallow

[Jetlink]

My 91 comp is shallow

In more ways than one right?

[dyost]

So it looks like the coupler key sheared off, split right down the middle. It doesn't look like there was any other damage caused to either the drive shaft, or the coupler. So what is my fix here? Get a new key and bolt everything back together?

Any concerns with reusing the coupler?
How about alignment, do I need to do anything to move the engine/trans around to make sure everything is lined up?

I can't figure out how this happened, there is absolutely no damage to my prop as far as I can see. No dings, no bent blades, no chips, nothing? I do have a stainless prop though so maybe it's just that much tougher than a 4 blade?

Please look over the pics and let me know what everyone thinks....

[dyost]

more pics......

[dyost]

Also, anyone know where to buy these keys and/or couplers if I need one?
Thanks,
-dy

[Jetlink]

You are running a stainless prop and not a brass one on your boat? I would address that while I was at it.

[Moor]

Looks like maybe the lock nut that secures the shaft into the coupler was loose? That's the only thing i can think of that would shear off the woodruff key like that. try skidim.com for the key. not sure if this one is the correct size for you: http://www.skidim.com/KEY-STRAIGHT-BRASS/productinfo/KEYBR25X2/

[Moor]

You are running a stainless prop and not a brass one on your boat? I would address that while I was at it.

is there a reason why a stainless prop isn't a good idea? I've always run brass on my inboards, just curious why stainless is a no-no.

[Jetlink]

is there a reason why a stainless prop isn't a good idea? I've always run brass on my inboards, just curious why stainless is a no-no.

With an direct drive or V-drive, there is no "weak link" built into the drivetrain such as an I/O or Outboard engine. So, with that being said, if/when you find something substantial with your prop you do not have a "Sacrificial" piece to prevent major damage. That is why brass props are the norm for our boats, the metal is obviously weaker and more forgiving saving the remainder of your driveline.

[dyost]

Yeah I've been meaning to get a new prop, not so much to just get brass but to get something better for the amount of weight I'm running in this boat and a better hole shot. Typically run around 3k in ballast and get a pretty decent wake for a 89 model year boat. Problem is I'm right at the threshold of too much for the engine, so you add a person to the boat and it will take 1/2 mile to plane out pulling a rider. So I'm thinking a newer designed, more efficient, smaller pitch prop would be the ticket.

But what are the thoughts on just replacing the key and putting it all back together to ride?

I called around a few places today, now bear in mind Kansas City doesn't have any proper inboard boat dealers so getting service advice or anyone who even knows how to work on this stuff is a stretch. But I made contact today with a guy from Summit Boats & Gear (a Nautique and PCM dealer) and the guy told me go to Ace Hardware and get a stainless steel square key stock to fit the coupler and use that. Is there any logic to the original brass key and the way mine sheared that is a bit of a fuse link in the case you hit something? He said some hardware stores might have brass also. I'm going to take Moor's suggestion and order a couple of the brass ones from Skidim. I'm out of town this weekend so will I would probably have them just in time to work on the boat next week and maybe get out next weekend.

Thanks

[tripster]

I would go with the brass if that is available from Skidim. If you hit something with your prop, the key will break before damage gets to the tranny. I am not sure the stainless would break.

[Moor]

With an direct drive or V-drive, there is no "weak link" built into the drivetrain such as an I/O or Outboard engine. So, with that being said, if/when you find something substantial with your prop you do not have a "Sacrificial" piece to prevent major damage. That is why brass props are the norm for our boats, the metal is obviously weaker and more forgiving saving the remainder of your driveline.

That makes perfect sense, thank you for the explanation.

[Moor]

I would go with the brass if that is available from Skidim. If you hit something with your prop, the key will break before damage gets to the tranny. I am not sure the stainless would break.

I was talking to one of the old time mechanics at my work, whos also a big boat/marine guy. He explained to me that the brass key way is the weakest point in the drive train, and is designed to shear off when the prop hits something major, before causing damage to the transmission. The coupler is actually machined to the shaft, and the tapered machining between the shaft and the coupler are what really hold everything together. The key way and set screw are there for alignment / safety measures.

i'd give a close inspection to the coupler and the shaft before bolting them back together. Make sure they seat properly with one another, or else you might be facing the same situation all over. If the coupler spun on the shaft, it may have scored the tapered mating surfaces on the shaft and coupler, preventing them making a proper connection.

[Moor]

It might be a good idea to use some prussian blue and relap the coupler to the shaft, like you would with a new prop, just to clean up the tapered mating surfaces. I've never have my couplers apart from my shaft, so maybe someone that has more experience can advise here.,

[chris young]

Like Michael hunter said, you should get the shaft checked before you put it back together. You can do it yourself, it's pretty simple, I think I paid about 100 bucks for this kit.

http://weldingsupplies.dynaflux.com/item/-i-crack-check-i-non-destructive-testing/-i-crack-check-i-kits/df315kit-s

You really only need to check around the keyways, especially the spot where the keyway is tapered into the rest of the shaft, both ends. You'll get enough in the kit to do the entire shaft if you care to.