whine from rear of 96 GTX

[artr]

Hello. I just started the season and noticed a mild whine from behind when cruising at 5000 rpm on my 96 GTX. Seems to be rpm dependent. Do not hear it at idle or other speeds. Do not feel any abnormal vibrations. Before I launched it I did a lot of normal maintenance. I greased the PTO fitting, checked the jet pump oil for water and condition of oil and pressure tested it the best I could with a pop-off tester I had made (the pump was replaced with a used one mid last season and changed oil then). I also installed a neoprene seal on the jet pump in an attempt to cure some cavitation on hard acceleration from a dead stop but that did not cure the problem (but it did slightly modify the position of the jet pump from last year). I did other normal things like clean the RAVE valves and changed oil filter and plugs that I don't think would cause a whine. Because I changed the oil filter, I ran it on the trailer with a hose for a couple of minutes to check oil flow and did not notice any abnormal sounds or vibrations then. What are things to check in the water? Because the sound is not real noticeable and seems to be at a specific RPM, is this something others have experienced and have let go for a while? Thanks for any advice on the subject.

 

[mikidymac]

These do have certain “sounds “ around that rpm but I would check the carbon seal since you still have some cavitation and ran it for a few minutes out of the water and could have damaged it.

Also the neoprene seal should not change the position of the pump.

 

[AKnarrowback]

How much of a change of the position of the pump did it make?

I rebuilt my motor and was so amped to test it out I forgot to do a good motor alignment. About 30 minutes into the test ride I noticed a whine slowly increasing in intensity that hit a point and stopped growing but was always there. It sounded like I had a crank bearing starting to go out.

It wasn't until I replaced the driveshaft that it got quiet again. I couldn't see any obvious damage to the splines but the miss aligned motor caused some wear in the PTO flywheel and original shaft that produced the sound.

If your new pump is shifted from where the original sat then it is possible you are rubbing the shaft and impeller splines in an area outside of their previous wear pattern on either the motor and or pump end.

Like Mac said, these do have sounds.

On the hard acceleration. My 97 GTX had terrible low end reving problems that I could not trace down. What cured it, in my machine, was pulling the ride shoe and wedge piece on the pump intake and resealing them to the hull. The wedge piece plastic appeared to have seperated 100% from the factory sealant and it litteraly fell off the machine when I was taking things apart.

On the carbon seal, I replaced mine with an old style original thru hull carrier bearing with two seals and have never worried about air or water leaks since. Sort of a home made retrofit.

Good luck.

 

[artr]

Thanks for the quick responses. I agree the neoprene seal will not change the pump position by very much but it was something that changed from last year. I really try not to run it very long on a hose, less than a minute. I have thought about the carbon seal from other posts I read about cavitation but I do not see any water leaks in that area when revving it in neutral tied up at the dock. When carbon seals start to fail, do they usually leak and fail gradually, or is it more catastrophic than that? I usually only put about 20-30 hours on it a season, so what I'm asking is it something I can reasonably put off for a winter project?

 

[mikidymac]

Once the boot that holds the carbon seal gets weak it can suck air into the pump under acceleration and still not leak water causing cavitation.

 

[GGuillot]

few minutes out of the water and could have damaged it.

You really tend to overstress this 'burning the carbon seal up" all the time, almost like clockwork anytime someone runs it on the hose. The man actually said a "couple minutes on the hose" and you think he may have damaged it? I ran my GSX recently on the hose for a least 5 minutes trying to unblock the pisser line.. Curious, after I shut it off I quickly undid the cover and felt the SS hat, it was barely warm.

I have no doubt in your experience you've seen them get burned up but I just think you overstress it, I don't think it burns up so easily after a few minutes and causes permanent damage.

 

[mikidymac]

You really tend to overstress this 'burning the carbon seal up" all the time, almost like clockwork anytime someone runs it on the hose. The man actually said a "couple minutes on the hose" and you think he may have damaged it? I ran my GSX recently on the hose for a least 5 minutes trying to unblock the pisser line.. Curious, after I shut it off I quickly undid the cover and felt the SS hat, it was barely warm.

I have no doubt in your experience you've seen them get burned up but I just think you overstress it, I don't think it burns up so easily after a few minutes and causes permanent damage.

Depends on how tight the boot is. I have seen new ones get way too hot to touch in less that a minute.

As to me saying don’t run them for more than a few minutes or you might damage them it’s a lot easier than telling everyone that might not know.... well, you might damage your seal or you might not, some get damaged and some don’t, some survive long runs and some don’t. Much easier to say don’t run for more than a few minutes or you can damage them. Sorry if I’m not being perfectly specific in every situation for you approval.

 

[AKnarrowback]

Can you put it off? Tough to say without being there.

Is there any way you can record the sound and post it? Video and youtube it?

If the pump is not really in a new position then I would take the time to pull the pump, open it up and inspect the bearings, make sure the impeller and liner are looking good. I would look into the carbon seal and confirm it is good. Make sure the drive shaft splines look good. Just a thorough inspection to be sure.

If you do all of those then you have eliminated all the moving parts outside of the motor and you either keep going into it or just run it and observe if it gets worse.

Trying to think of anything else, grabbing at straws here......... Motor mounts solid? Grab the pipe and rock the motor around.

 

[artr]

Thanks for the replies. Because the sound is slight and the engine noise is high, I'm not sure about a recording but I will try. The jetski is 220 miles from my home and when I go to the lake and stay there I try to just use it except if it is something major. I try to preform out of water repairs over the winter. I will inspect the carbon ring as best as I can and maybe try a zip tie on the boot to see if it improves the cavitation that occurs under hard acceleration from a standstill. I will also try to inspect the motor mounts. I will monitor the situation and if it gets any louder, I will change the jetpump to a spare that I have on hand.

 

[artr]

Sorry for the delay but I was at the lake this weekend and did some troubleshooting with the ski in the water. I looked into rocking the engine by hand and could move it about a quarter inch. The motor mounts were tight but the crescent shaped engine support bracket at the rear of the motor was not. I tightened the 5 bolts holding it to the motor and then I could not rock the engine any more. I thought this might be a reason for the whining sound. I also wanted to tighten the 2 radiator hose clamps that are on the rubber boot over the carbon ring to see if there was an improvement in the cavitation that occurs from hard acceleration from a standstill. I did that and as I tightened the clamp on the carbon ring, the ring backed off slightly and allowed some water in. After tightening both clamps, I noticed I could move the carbon ring side to side (the ring was not tight on the drive shaft). No water leaked when moving the carbon ring and I ran the engine with the ski tied to the dock an no water leaked when revving the engine either. I went for a ride and still heard the whine and the ski still had cavitation during hard acceleration.
I recorded a voice memo on an older iphone and it's attached. I listened to it with a really good pair of headphones and can make out the whine although there is a lot of engine and wind noise. It is most pronounced after 40 seconds into the recording. It is not loud but something that I've noticed this year. It reminds me of the whistling sound a large jet airliner makes, but much lower. I would be interested in any further thoughts you have. Thanks.

 

[GGuillot]

I listened to the audio, sounds normal to me. If you're getting cavitation, I'd check the driveshaft being bent and the wear ring. When you have the pump off check for the neopreme seal between the pump and the hull plate, check the sealing around the wedge.

The engine alignment could be off, but you'll need to get the tool to verify that.

 

[mikidymac]

Also the carbon ring is not tight around the driveshaft as the ID is much larger than the OD of the shaft.

 

[artr]

I am updating this post because I just removed the jet pump and drive shaft to inspect and replace the carbon ring and hat for cavitation problems. What I noticed was there was no rubber bumper on the drive shaft end at the impeller. What must have happened is my original jet pump seized due to water in the bearing area. The bearings were destroyed and probably got pretty hot. The rubber bumper must have also got destroyed but I did not notice that when I replaced the jet pump with a used one. I know the bumper was there previously because of an older picture I had. Nothing had changed in terms of cavitation that I was trying to fix except I noticed the mild whine mentioned above developed. I'm thinking that the whine was related to the rubber bumper missing.
My question is if there could be other damage I should look for due to running without the rubber bumper for a season. The splines on both ends of the drive shaft look fine. There is a raised edge on the driveshaft that only lets the driveshaft go so far into the impeller with the oem impeller boot installed. I do not feel any gear lash when the drive shaft is inserted into the impeller. There is about 1/2 mm of end play on the impeller shaft in the pump which should be ok according to the spec for a 96 GTX pump. Thanks.

 

[mikidymac]

It shouldn't have caused any damage.

 

[Legacy37]

How much of a change of the position of the pump did it make?

I rebuilt my motor and was so amped to test it out I forgot to do a good motor alignment. About 30 minutes into the test ride I noticed a whine slowly increasing in intensity that hit a point and stopped growing but was always there. It sounded like I had a crank bearing starting to go out.

It wasn't until I replaced the driveshaft that it got quiet again. I couldn't see any obvious damage to the splines but the miss aligned motor caused some wear in the PTO flywheel and original shaft that produced the sound.

If your new pump is shifted from where the original sat then it is possible you are rubbing the shaft and impeller splines in an area outside of their previous wear pattern on either the motor and or pump end.

Like Mac said, these do have sounds.

On the hard acceleration. My 97 GTX had terrible low end reving problems that I could not trace down. What cured it, in my machine, was pulling the ride shoe and wedge piece on the pump intake and resealing them to the hull. The wedge piece plastic appeared to have seperated 100% from the factory sealant and it litteraly fell off the machine when I was taking things apart.

On the carbon seal, I replaced mine with an old style original thru hull carrier bearing with two seals and have never worried about air or water leaks since. Sort of a home made retrofit.

Good luck.

Would love to know more about this retrofit

 

[AKnarrowback]

The only catch is you have to keep an eye on it and keep some grease in the bearing. In my experience it seals more reliably than the carbon ring, but it can destroy the hull fitting if it seizes. I prefer it because I am into the pump enough that the carrier gets cleaned and regreased multiple times a season and I never want water leaking in.