Cavitation issues (mechanical grinding/vibrating)

[SJBrit]

Have you checked that it's not something simple like the pipe rubbing and vibrating? A B-pipe will make a heck of a noise vibrating against the bed plat or the side of the ski. Shakes the whole ski and feels like it's about to blow.

 

[McDog]

Yeah it's definitely not cavitation because I noticed that it was doing it on the trailer today.

That's actually good news. Anything else will be easier to fix. A midshaft bearing going out sounds like a wounded elephant. A torn midshaft housing will be really loose and could be your problem too.

 

[Waternut]

Have you checked that it's not something simple like the pipe rubbing and vibrating? A B-pipe will make a heck of a noise vibrating against the bed plate or the side of the ski. Shakes the whole ski and feels like it's about to blow.

That was certainly something I didn't think about. I went and checked those but because the stunt hull is wider than normal, I can fit my hand between the hull and the pipe. Also, since the waterbox is mounted so far forward in the hull, the chamber is angled slightly up so there is plenty of clearance above the engine mounts. I have at least eliminated the intake grate though.

Check your coupler condition and alignment first , Motor mounts ''broke ,loose''' then I would pull pump look at the shaft splines , Those would be my starting points . cavitation does not GRIND that I know of !

I have noticed that the grinding noise or whatever it is, is typically around that low rpm range when the engine vibrates the worst. I'm beginning to wonder if I damaged one of the engine mounts when I was putting the engine in...

 

[Waternut]

Ok so I pulled up on the engine at all the motor mounts and it appears that all mounts are fine and don't separate. However, the wounded elephant reference got me thinking...

Cranking sounded normal the day before I fried my crank last season. After the full rebuild, it sounded horrible when cranking but once it started, it sounded and operated perfectly normal. I thought it would go away after breaking in the engine but when it didn't, I just said screw it.

So based on this video, do you think this sounds like a midshaft or starter issue?

 

[Flash-FX]

I'd like to see you get it going smoothly.

2 things from that short video....

1- Ground those plug wires.

2- Is your bendix always engaged?

 

[Waternut]

It's a total loss system and I was running with the ignition off so it wouldn't damage the coil. The bendix pops and in and out like it's supposed to. It would stick a little after Daytona but some I put some WD-40 on initially, then some grease, and it works like a champ again.

 

[SurferSmurf]

ive been fallowing this for a couple days and couldnt come up with anything till now. pull your water box out and shake it. my baffle inside actually broke in 2 big pieces and made a similar sound. drove me nuts cuz it felt fine and only made noise on the trailer or at certain times. i only found it when i changed pipes and had the water box out.

 

[Waternut]

ive been fallowing this for a couple days and couldnt come up with anything till now. pull your water box out and shake it. my baffle inside actually broke in 2 big pieces and made a similar sound. drove me nuts cuz it felt fine and only made noise on the trailer or at certain times. i only found it when i changed pipes and had the water box out.

It's a Factory Pipe waterbox and it doesn't have baffles. However, it is possible that the waterbox is vibrating excessively since it isn't really mounted in the hull. It's just kinda wedged in there. I added some turf to it but it could be hitting a place that I didn't turf.

 

[SurferSmurf]

are you sure the factory pipe water box does not have a baffle at all? i thought they all had something.

 

[Waternut]

They have a small curved plate welded to the upper surface between the inlet and outlet. I guess it's still possible that's loose.

 

[Waternut]

Cross your fingers for me. I found another possible cause... I added additional bolts in the center of the pole bracket to help support it. Based on the gouges, it looks like the front two bolts were banging against the waterbox. The picture shows the gouging and the bolt removed. Might explain why every time I landed a jump it would make the noise since the waterbox would slide forward a little until the vibrations bounced it off again. Hopefully that solves it...

 

[SurferSmurf]

told ya it was a waterbox issue, haha. good luck hope thats it.

 

[Shonuff]

Now I'm emotionally invested in seeing if you get it fixed.

 

[McDog]

Now I'm emotionally invested in seeing if you get it fixed.

Awwwww! That's so sweet. Having the glow must be good for your soul.

I wish you luck but I'm not emotional about it.

 

[SurferSmurf]

status????????????????:dance:

 

[Idok]

motor bed plates vibrating against kenney keepers?

 

[djkorn1]

Driveshaft shifting forward and back??? banging into the impeller?

 

[Waternut]

The midshaft/engine couplers have settled out of alignment and I just finished realigning them. There is very little difference in coupler gaps now. Worst gap difference between lower right (0.035") and upper left (0.043") fingers is 0.008" (0.2mm) with no visible gap if I put a straight edge across the couplers. I don't know if that's close enough or not but it seems like everyone just lays a straight edge across the couplers and calls it good anyway.

Driveshaft is solid.

I've gouged up the kenny keepers pretty bad in the past because they were too close to the bedplates. I took a little metal off the keepers this time so they'd fit better. It's possible that's the cause. If I still have problems with this new alignment, I'll pull the keepers for a ride and see if the problem goes away. I'll try to ride Tuesday or Wednesday to see how it does.

 

[Vaunster]

done?

so is problem sorted?

ive jut bought a 95 SJ & want to learn as much about possible problems as i can.

hope u got it fixed

cheers

 

[Waternut]

Nope... never figured it out. Even when I pulled the engine and tried to sort everything out that could potentially be causing the problem, it still exists. However, it's my belief that the problem lies in my aftermarket hull and not SJ's since this problem didn't exist with the same components in my SJ.