650/X-2 Any ideas on what caused this...

[Wilke]

This happen while riding surf last summer. I was unemployed at the time, and jetskiing was one of the financial sacrifices I made so I never got around to getting the ski back in the water until now. Anyone have any idea on what would cause a driveshaft to snap like this? As you see in the pic I have a replacement, but I'd like to figure out the cause and fix it, or maybe it was just a freak failure. No visible damage to the impeller to suggest it sucked something in. And the motor, coupler, bulkhead bearing, and everything else on the ski is undamaged. I'm stumped.

 

[Joker]

Broken motor mount?

 

[cattledog]

sometimes things just break, you know it wasnt for to much power lol, put other one in and have fun

 

[Snivilous]

Make sure everything is torqued down. As joker said, I would guess the motor somehow moved or the pump assembly moved so that it snapped where the driveshaft is secured in the thru hole for the hull. Though I don't see how that would happen unless the pump wasn't secured at all and someone jumped or something heavy fell or pulled it down. Likewise with the motor (and very unlikely since the coupler would move instead of the entire driveshaft flexing).

You just found it this way? It didn't happen last time you rode it?

 

[Joker]

This happen while riding surf last summer.

^^^^^^^^^^

 

[Snivilous]

Can you get a closer picture of the two halves? Did it actually just snap, or did it twist? If the driveshaft was spinning, and the engine for what ever reason came loose, then I can see the crankshaft and driveshaft staying mated because they'd be rotating as one, so it could conceivably twist the driveshaft apart at the location where it's fully constrained (driveshaft seal). I doubt the crankshaft and driveshaft would be stuck together so well for that happen, but if it was a big impulse. Then the other idea that if the pump came lose, though it would have to be pulled down (which obviously doesn't happen when you land off a jump), which I would think would be more likely.

What's the distance from the break to the edge of the coupler? Then you can easily figure out which end of the driveshaft was being loaded for it to break.

 

[Wilke]

sometimes things just break, you know it wasnt for to much power lol, put other one in and have fun

True statement. This is my thought too, it just broke. No underlying issue.

 

[Wilke]

Snivilous - I didn't just find it broken I noticed as soon as it happened, wasn't after a huge jump or anything, just on my way back in and I throttled it to jump over some whitewater and it just let loose, about 50 yards from shore. My first thought was broken mounts and the motor shifted away from the coupler or maybe just a sheared coupler. The pump is still solidly attached and sealed, and all the motor mounts are intact. I'll get a picture of the actual break, but its located just behind the thru hull bearing, pump side.

 

[jamesgunter68]

theres 3 different things that could have caused it in my opinion
1: it was a freak accident and just broke (seems pretty likely with the statements above)
2: torsional vibration- when the crankshaft or driveshaft twist so much that it snaps (doesn't seem likely with all your bearings and everything still being good)
3: liner vibration- when the motor or pump move so much up, down, or side to side that it gives out ( maybe a problem)
make sure to check your alignment before you ride again

 

[kevbo]

It is unusual to have them break like that. Consider it a fluke and move on.

 

[dbattersby20]

Also, it looks like it snapped where the shaft contacts the bearing? Make sure there no lip in the bearing which could grind into the shaft

 

[Wilke]

Additional picture of the break. It broke right behind where the shaft touches the bearing.

 

[Snivilous]

Was it always that rusted looking?

 

[Wilke]

No it had some rust on it when I originally installed it but not that bad, it sat for close to a year after it broke and I don't think i even bothered to hose it off, it still has sand on the footwells and in the pump area. Just flushed the motor and parked it.

 

[Jet Ninja]

sorry to be off topic but i have a question. when the link says this topic is 650/x-2 does the "650" mean 650sx standup? or is that an x-2 motor

 

[DAG]

If the pump came out of the water and rev'd to the moon and the ski came back in contact with the water, the intent hookup could torsion shear the shaft like that. Typically only with big hp and pump combo's

 

[Snivilous]

sorry to be off topic but i have a question. when the link says this topic is 650/x-2 does the "650" mean 650sx standup? or is that an x-2 motor

The 650 motor in the 650sx and X-2 are the same motor, but yes, 650 for the title means 650sx/X-2.

 

[Crab]

Most likely alignment, make sure everything is centered up before the final tight down of the bearing housing, it will flex but should be iin the middle of the range with no pressure on the bearings. I ususally align the motor with the housing way fwd to center the driveshaft, then when Im happy with motor alignment push it back....its been a while tho.

 

[Jet Ninja]

The 650 motor in the 650sx and X-2 are the same motor, but yes, 650 for the title means 650sx/X-2.

ok thanks