Strangest mechanical failure...sudden as heck. 24Ve MP 340 year 2006

[dakota4ce]

The scene:

Surfing along normally. Rider falls, circle back and shut boat down for rider change. Start boat back up, shift to forward gear, driveline clunks and motor dies. WTH? Try again, same. Jump in, Check prop for entangled rope or something, nothing there. Check tranny fluid level; good. Couple more tries, which I am certain is dumb, same result. Get towed in, get under boat to look, nothing fishy there.

While on hoist, motor off, prop turns 45 degrees by hand then HARD stop. Happens both ways, back and forth. Unsure if a neutral boat does this or what problem this indicates? Before this had never hand turned prop. I am sure this is likely not good!

No fluids in bilge that I could see. V drive? Tranny? What fails like this?

Completely normal up until attempted restart.

Chime in all the experts! Please!

[ChrisSnow]

It should turn relatively freely in neutral. Sounds like either the transmission or V drive has had a failure which has caused the gears to be destroyed and has now got jammed.

I guess pull both out and see which has failed. May be repairable or worst case you will need to replace one of them.

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[lee]

Did you check the coupler bolts.

[dakota4ce]

Coupler bolts had me excited! They appear to be normal, but can't snake the hand around to feel the 4th. Need someone to turn prop while my face and hand are feeling for them.

I also would like to listen to where clunk comes from.

I need a clone of myself.

[IDBoating]

Sounds like either the transmission or V drive has had a failure which has caused the gears to be destroyed and has now got jammed.

Sad to say, I agree with the prediction of a mechanical failure in the tranny or v-drive. When the transmission is in neutral, you should be able to rotate the prop by hand in either direction (with some effort, to overcome the various frictions in the system).

A friend once had a similar mystery. Parked the family van at a grocery store, came back out, turned the key, the starter tried to turn the engine over and the engine simply wouldn't budge. Got to the point where they pulled all the plugs and still couldn't turn the engine over even without compression. Absolutely mystified - the engine had been running PERFECTLY minutes before. We all had vast ideas of what had failed internally. What really happened? The starter lost a tooth off its Bendix gear, which then jammed in place, preventing anything from turning. Swapped out the starter and everything was perfect again at a fraction of the cost we all feared. Moral of the story: Sometimes a simple thing will look much worse than it is. I hope that's the case here.

While you're at it, make certain your tranny neutral switch actually works. Under normal circumstances your tranny and v-drive shouldn't be exposed to the (relatively) sudden shock of the engine starting and stopping. But if that switch isn't working, you could be hitting the tranny and v-drive with unusual forces, perhaps explaining why you could lose a gear tooth.

Report back!

[rensink]

Let me know if you need help I'm off on Wednesday otherwise I can swing by some night after work and give you a hand.

[boatwakes]

V drive gear failure, trans failure wouldn't allow engine to run, but when you turn the prop shaft or shift into gear, the drive is then just spinning from the input torque, either through the engine or from hand spinning the prop. There is a dipstick on the v drive, check for fluid there but you're missing a tooth on the drive gear and i would recommend replacing the whole unit. It's easier, faster and way less down time.

[dakota4ce]

V drive gear failure, trans failure wouldn't allow engine to run, but when you turn the prop shaft or shift into gear, the drive is then just spinning from the input torque, either through the engine or from hand spinning the prop. There is a dipstick on the v drive, check for fluid there but you're missing a tooth on the drive gear and i would recommend replacing the whole unit. It's easier, faster and way less down time.

Thank you for your inputs. I figured this was the case. Any place to source a rebuilt unit? All I have seen are EBay brand new units, at roughly $2500.

Also, does this have anything to do with running at the rubrail while surfing? Like a fluid starvation issue, or excessive heat issue? Wanting to prevent the same from happening again.
BTW fluid looks normal on Vdrive dipstick.

Thank you again guys.

[boatwakes]

What's the ratio on the v-drive and I can link you one. But before we go down this route, get someone to turn the prop while you're looking at the coupler just to make sure there isn't something stuck between the coupler bolts and the housing. Use your phone to take video from a bunch of angles and listen for the noise in the vdrive when it stops rotating.

[ChrisSnow]

I'd strongly suggest pulling it apart and finding out exactly what the issue is before buying any parts.....

[dakota4ce]

Update

image.jpg

What's the ratio on the v-drive and I can link you one. But before we go down this route, get someone to turn the prop while you're looking at the coupler just to make sure there isn't something stuck between the coupler bolts and the housing. Use your phone to take video from a bunch of angles and listen for the noise in the vdrive when it stops rotating.

Left it with a mechanic as I headed off to work to help diagnose. He tore into it. He said there are some sheared grade 5 bolts in the area where the tranny and Vdrive join. We talked super fast.
Also said he thinks the tranny and Vdrive are both fine, that the sheared bolts were causing the binding. It gonna replace seals/gaskets that apply and bolt back up with grade 8 bolts....is this odd as hell or what? Using grade 8 feasible?

Some pics:
image.jpgimage.jpgimage.jpgimage.jpg

[dakota4ce]

Sorry using my phone is a little rocky!

[ChrisSnow]

Things like that don't just shear! Either there's a serious problem somewhere or it worked loose and hit something.

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[dakota4ce]

Things like that don't just shear! Either there's a serious problem somewhere or it worked loose and hit something.
T
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I agree odd as hell! How would this occur? Worked loose then ripped the heads off the others when it was too loose?

[boatwakes]

REPLACE THE TRANS OUTPUT COUPLER FLANGE!!!! (Male side). Look at the bolt hole, it's ovaled AND raised on the face. The original problem was improper torque on that bolt and it backed out. Loose bolts in that area cause flange separation and because the output is both forward and reverse on that flange, the slop may have ovaled ALL THE BOLT HOLES. Ive seen it on shaft couplers when improper hardware is used. You're already there, replace the trans output shaft or at least machine the surface flat. If the surface is not true, you're playing with fire and it will happen again. I would not use grade 8 but instead replace all bolts after verifying the threads are clean in All the holes and use red loctite and proper torque. DAMN!