2 Season Old Driveshaft Failure

[JKMike]

Hey yaw,

This past weekend I discovered that my midshaft was essentially seized onto my driveshaft. Everything still spun nice and easily but It was a royal pain to get the midshaft off the driveshaft. Ended up having to use a 10lb slide hammer. Anyways I'm trying to figure out what could have caused this and I pretty stumped. I was meticulous when I aligned everything when i built the ski 2 seasons ago, down to the point I was using 0.005 shims.

Here are all the details for my setup
Hull Carbon xfr
155 OEM pump used housing but all internals and driveshaft only have 2 seasons on them
Midshaft housing, bearing and seals are 3 seasons old.
The midshaft itself age is unknown but it appeared to be in good charger.

 

[Sasquachcrap]

I believe your alignment is great.

Yamaha uses a carbon steel tip on some shafts for added hardness and wear resistant. It’s much harder but carbon steel is more susceptible to rust and galvanic Corrosion. I sure you greased it? This will help slow the process but (and I’m not knocking them some times it’s all we got) sbt replacement shafts are designed the same way but I think there metal quality it’s on par with Oem.

Galvanic corrosion is a real concern in carbon hulls and/ or saltwater.

 

[JKMike]

I packed the midshaft with the blue BRP grease when I assembled everything. That stuff is the most water proof grease I know of. As for the shaft I am told that it is a OEM shaft that's been cut and welded to length. I will say that when I was aligning the Pump there was definitely some runout in the shaft when rotated but I shimmed it to get the best overall alignment. If you look at the pics it looks like the o-rings wore groves more on one side of the shaft than the other. I guess going forward I will just make this a much more frequent service item. At least twice a season.

Do you know if there is anyone out there who makes either all stainless shafts or solid billet ones? I know Torrent has one but its only for a Setback pump.

 

[Freakrider]

The short answer is driveshaft runout causes midshaft seals to fail, allowing washout of spline grease and corrosion/rust to form. I had a new driveshafts build fail after one year like that in saltwater from shaft runout. The replacement shaft had runout so I pulled pump every 4 months and found water on splines. I would wet vac it dry and re-grease for maintenance. I now have splines cut to length, setback, used oem driveshafts without significant runout; problem solved. JKMike you seem to have figured this out the hard way like myself.

 

[JKMike]

The short answer is driveshaft runout causes midshaft seals to fail, allowing washout of spline grease and corrosion/rust to form. I had a new driveshafts build fail after one year like that in saltwater from shaft runout. The replacement shaft had runout so I pulled pump every 4 months and found water on splines. I would wet vac it dry and re-grease for maintenance. I now have splines cut to length, setback, used oem driveshafts without significant runout; problem solved. JKMike you seem to have figured this out the hard way like myself.

So where did you get those shafts?

 

[Sasquachcrap]

Those shafts are cut shorter and the spline section welded back on. It’s a fine way to do it , but it takes a LOT of effort to re true after welding.

I’m not saying the manufacture didn’t do this. Just that I know what it takes.

Unless a customer specifically asks for the hardened tip and a cut and weld I don’t do it. I cut an Oem shaft to length and re spline. There is much less runout this way. And I have had no issue with spline strength even with the strongest motors. Given the alignment is correct.

 

[Freakrider]

So where did you get those shafts?

I get them from SNL Industries, the above poster or Roland's Powersports in Tampa who has XS cut & spline them from oem couch shafts.

 

[Sasquachcrap]

In my opinion not as bad. Carbon is conductive. And this is the most sacrificial part. Maybe we could add a anode to the pump body?

 

[Freakrider]

If you have a true driveshaft and the splines remain dry and well greased because the midshaft seals aren't worn down from a driveshaft with bad runout, it will not develop this issue from my experience with carbon hulls.

 

[kevbo]

Carbon is very noble and mainly damages aluminum. You just got a lot of water in the splines. There is a couple of O-rings in the mid that seal to the driveshaft. That is what ultimately failed.

 

[Freakrider]

Carbon is very noble and mainly damages aluminum. You just got a lot of water in the splines. There is a couple of O-rings in the mid that seal to the driveshaft. That is what ultimately failed.

Exactly right ! Caused by a wobbling untrue driveshaft rubbing down the midshaft seals.

 

[kevbo]

Superjet driveshaft to midshaft engagement is too short. That is why we have so much trouble with water leaks and overall wear. I dont know why the aftermarket keeps producing the same old "bad" design. There is plenty of room to make the splines longer and set them deeper in the shaft. Yamaha did this to their big couches and they last forever.

 

[Sasquachcrap]

You can set the splines as deep as you want but with out a new midshaft design it doesn’t matter. I’m all for a midshaft with longer internal splines but I can’t make them. And making the driveshaft splines longer then 2 inches (as I do) is fruitless.

 

[JKMike]

In my opinion not as bad. Carbon is conductive. And this is the most sacrificial part. Maybe we could add a anode to the pump body?

I like this idea and have considered doing it before. Maybe mount 1 or 2 on the pump somewhere?

 

[Big Kahuna]

There was that guy down near Panama City I think that was making the once for Blasters. Think it had just a square taper to it. They were listed on this site.........

 

[Sparkplug]

I've never put the o rings on a drive shaft.

I've pulled many, many, many skis apart that didn't have them

Pulled dozens of surf skis apart. My surf blaster fused the pump to the bolts from corrosion.

Never, ever, seen a driveshaft look like that.

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[Sasquachcrap]

I hate to ask because I think xscream uses some sbt shafts for cores. Was it from them? Their metal (sbt). Is junk. I can tell as soon as I put a cutter Into it if it’s quality material. Post a picture of the clean bare shaft in the rear with the bearing removed and I can tell you if it’s Oem or not just by the coloration.

 

[hornedogg79]

I had one fail exactly like this 5yr ago. The corrosion started at the weld not the orings. I switched to a shaft made from one piece and haven't had a problem since.

 

[Sparkplug]

I had one fail exactly like this 5yr ago. The corrosion started at the weld not the orings. I switched to a shaft made from one piece and haven't had a problem since.
View attachment 424488

That looks like a drive shaft placed in side a wallowed midshaft. And ran. And fretting tore it up. Your splines have lost meat about 2/3 the way up. From your pics anyways

The op shaft appears to be the same wear down the entire length of splines, and not much wear. But still looks like fretting because of the striation imo. Never seen metal of these types corrode like that. Makes me think you guys got sub par material in the shafts. Who knows. I dont

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[JKMike]

I got a bit more information about what likely happened. It looks like my shaft likely had the extra hard splines that comes on some Yamaha triple skis. The end of the shaft where the splines are is fusion welded on the main shaft by Yamaha. They are extra hard to handle the triples power, but the downside is they are less corrosion resistant.

Up untill now I didn't even know that this was a thing.