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Sudden vibration.

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Kris69

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Hi everyone! I have this Ski and its supposed to have a rebuilt motor 14 hrs old. So i assume its run in.
Racing around on the water yesterday at Eildon and it suddenly developed a bad vibration like a switch was flicked. Turned back and headed to shore. It ran fine otherwise and kept it at 5500 to get back. Definitely no knocking in the motor but starting it on the trailer the vibration is very noticeable.
I haven't been able to check anything apart from the engine mount and they aren't broken.
Can anyone point me in so direction as to what to look at/expect?
I thought this was a 2004 but looking at the Hull number it ends in 03. Does that make it a 2003 model? My other one is definitely a 2004 and end in 04.
Also it has a hose on top of the jet pump and goes uo into the hull while the 04 model doesn't. What's it for?
Kris
254.jpg
255.jpg
 
Check the pump and impeller. Typically when you get something lodged in it, it will cause a bad vibration.

The last two of the VIN is always the model year.
The hose is for the OPAS steering assist. It pulls them up out of the water at high throttle for less drag.
 
Thanks mate! Will check when i get home.
Is that feature deleted from the 2004 model or is it done differently?
 
So far i have removed the jet pump and nothing lodged in the impeller. Compression is 152psi Mag and 155 PTO. Plugs look the same and no fouling present.
Nothing broken as there is no knocking etc.
I couldn't remove the drive shaft as the sealing hat is stuck. Did comp test and also started it up and can feel the vibration. Throttle response seems the same (didn't do a big rev).
I did notice while the shaft was hanging there, there is quite a lot of up/down, circular movement. Would that be considered normal?
 
I would try pulling the spark plug caps off the wires, trim off 1/4" and thread the caps back on. Then install a new set of NGK BR8ES plugs.
 
First place I would check is the motor mounts. Grab the engine and try and shake it back and forth and see if it moves at all
 
Possibilities:

Output related:
Bent impeller blade and is now out of balance or bent the pump shaft.
Or something hit the driveshaft just the right way to bend it.

CARBON SEAL WOBBLE! Just thought about that. IF the carbon seal does not stay seated properly and starts walking around, it will create a wobble that is noticeable at idle in or out of the water and at speed.

You can wear it back in straight again with a little bit of valve grinding compound and a good cleaning. Also you might have to realign the accordion boot so the carbon ring sits flat on the flange.

Impeller unscrewed itself from the jet pump ( I've had something similar on mine where the impeller wasn't torqued down enough and it started working itself loose. It couldn't come off but it would wobble and only the right speed would make it smooth out.)

Pump seal failure leading to water ingress and bearing failure.


Engine related:

PTO flywheel could have unscrewed slightly and it won't come out fully but can still screw and unscrew. But I doubt this one.
Mag side flywheel can come loose and wobble if it wasn't assembled correctly. I haven't seen one come loose or strip but I have seen a few not torqued down properly. Almost feels like something is going to break while torquing it down properly.

Counterbalance shaft bearings could have started to fail.

Crank twisted....

Can you take a short video of it running and remove the pto cover.

Also see if you can shake the engine to make sure its not just a motor mount that is loose.

If I remember correctly the RFI only run's on one cylinder at idle and kicks in both after slight bit of throttle so in the video just touch the throttle so you can hear both kick in.

Since it was just rebuilt I wonder if the builder oiled the counterbalance cavity.
There are drain and fill plugs on the back left side of the motor. Worth draining the fluid out to look for debris or just if there is any fluid in there.

There are only so many things that it could be.
 
If you could pull the pump and driveshaft then start it you would at least be able to isolate the problem.
 
Just a matter of getting the carbon seal flange off the driveshaft. They can be difficult sometimes.
 
Hi Guys. I still haven't had a chance to continue working on it but yes i want to remove the shaft and then start it and see what it does. The sealing flange was stuck fast.
I'll also make the video as suggested but its harder to hear the vibration out of the water but i think i can feel it. Will start my other one up to compare.
The mounts seem fine but only rocked it side to side, need to try lifting it.
I had a Datsun 1600 (P510) that ended up having a loose flywheel and it feels similar to this while in the water.
Will swap the jet pump over from my other ski too and see if it stops.
Will keep you all posted! Thanks again!
 
Here are 2 videos guys of the driveshaft in a lathe. It wobbles enough i think to cause a vibration in the ski. On the trailer its difficult to feel the vibration with the shaft in as i guess as there is no load on the engine. I couldn't see and noticeable damage to the impeller blades either but i can't remove from the pump housing as yet as i don't have the tool for it. What does everyone think?
 
It never loads for me.

What "tool" do you need to remove the pump housing? If the driveshaft is out isn't the pump already off?
 
Ah ok. It plays for me so maybe only because i posted it?? Sorry guys.
The tool i was talking about was to remove the Impeller from the pump housing. I have one now though.
 
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