Can't figure out root cause of cavitation

[ligiman]

Hello everyone.

I originally posted another thread about cavitation occurring in the port side of my 2009 SeaDoo Wake 230 with twin 215 HP SC immediately after a SC rebuild. Everyone on the forum assured me that the rebuild could not cause the cavitation, although due to increased power, it could have made the symptoms of an already existing issue more apparent.

Here is the quick backstory: right after picking up the boat from the local SeaDoo dealer after the twin SC rebuild, I noticed the port side cavitation after about 45 minutes of operating the boat. I took it back in, and the SeaDoo dealer said it was a damaged impeller, and said that they needed to replace both impellers to the tune of $1500, as they needed to replace both of the aftermarket SS impellers with OEM ones so that they match. I thought that was ridiculous so I took it back to the place I bought it from to check out. That was about 6 weeks ago. They have checked out the impellers (they were in excellent shape, and they even swapped sides, and the cavitation stayed on the port side), the wear rings, which are also in great shape, and replaced the carbon seal on the port side. The cavitation is still occurring, and they are perplexed as to what else it could be. (They said something about taking off the ride plate and lubricating something a little deeper in, but I wasn't quite following what they were saying). Anyway, it seemed they were not too hopeful that this last effort would solve it, but didn't know what else to do or check after that.

Soooo, my question to all of you experts out there is this: if it is not the impeller, wear ring or carbon seal/drive shaft seal, what other components or things could cause the cavitation? The repair place seems to be out of ideas, and I really don't agree with the SeaDoo dealer''s diagnosis nor want to pay their exorbitant prices.

Thanks in advance to any suggestions, and please let me know if I can provide any additional information.

 

[roju6]

I have the almost identical boat (2010 Wake 230 with 255's), and when I bought it 6 years ago, I had a little cavitation on one engine. I didn't know the backstory on the boat or if/when superchargers had been rebuilt, so I had those done that first winter. That solved my cavitation issue.

If yours started after the supercharger rebuild and nothing else changed, that is where I would be starting. It is possible something was assembled incorrectly, as slim of a chance as that might be.

Process of elimination with no other changes would point to the rebuild as the first culprit, IMO.

*Edit: I just went and read the other thread, I was assuming there was no other damage caused by the removal of SC's. I know others said no possible way a SC rebuild can cause cavitation or slip, but if nothing else has changed and checks out, it's still the first culprit to me, take it for what it's worth.

 

[ski-d00]

I would switch driveshafts and check engine alignment and motor mount condition while I was there. A slightly bent driveshaft that is not noticeable to the eye will cause cavitation. All it takes is a little bit of vibration(this won't be noticeable by looking or listening) introduced into the drive system to cause minor cavitation which a bad motor mount or slightly misaligned motor can cause.

The supercharger has nothing to do with the cavitation but it probably brought it to light once the engine started making more hp.

 

[Joe Starbuck]

Or, they dropped the SC on the driveshaft while removing it. However, you said the shop replaced the port shaft seal, so that is not the issue, unless they really whacked it and bent the shaft.

Even if this is an old problem just brought to light by the restored power level, the OP has checked most of the usual causes. Since they took the pump off, did they make sure to replace the thick gasket that seals the pump to the hull? Shaft alignment (motor alignment) as mentioned by @ski-d00 is also important to check.
Lastly, similar to alignment check, some boats have shims between the pump housing and the hull, at least according to my shop manual. If you loose them, alignment is altered.

 

[ligiman]

Thanks for everyone's posts and suggestions. I just received a call from the repair shop and they said they think they resolved the cavitation. It seems the shaft seal was not seated correctly when they replaced it, and once they seated it better (put some lube on it to make it slide into place better, I think he said), they ran it several times and did not experience cavitation. I will pick it up and run it for a while, and if that does NOT resolve it, we will look at a possible bent shaft or misaligned motor/mount next, but here are fingers crossed...

Thanks again!