Screeching sound from jet pump

[Luke42_02]

I recently replaced my impellers and wear rings as part of the rebuild process. The wear rings were a really tight fit, in fact the motors wouldn't even turn over until I oiled the impellers with WD-40 and cranked the starter 30-40 times. This cut shavings out of the plastic wear rings. I do not think the thrust bearing was pinched since the pump spun freely in between the parts where it contacted the wear ring.

The problem is that my Starboard pump makes an intermittant screeching sound. The sound got better throughout the 30 minute test run. Everything runs fine, RPMs are good, speed is 50-55mph. When I start the engine on the trailer, it does not make the sound. I was actually able to record the screeching sound which you can find here:

https://www.youtube.com/watch?v=yczGH4yvqng

The sound starts about 1-2 seconds after I hit the throttle in the video. You can see what my hands are doing with the throttles for most of the video.

I assume I need to take the pump apart and make sure everything is ok in there.

 

[Luke42_02]

I forgot to mention, this is also without the director nozzle being sealed to the back of the pump. I just bolted it down until I knew it worked.

 

[LouDoo]

I'm not sure I understand your second post. What year and type boat is this? And are you certain that when you re-installed the pumps you used the correct shims (if any) and you re-installed the pumps in their original locations?

We need to know year and type boat to determine if you have carbon seals or carrier bearings.

Lou

 

[Luke42_02]

Sorry, had it in the original post I typed but that one was lost in a refresh. It's a 1998 Seadoo Speedster. Carbon seal.

 

[Luke42_02]

Also sorry for not responding completely. No shims were present. Pumps were replaced on the same side they were taken from.

 

[Luke42_02]

Ok, so I took the pump off and I'm encouraged by what I saw. The new SBT wear rings were slightly oblong in shape, so the impeller has cut a groove on both sides. The impeller spins freely, but there is still a small part rubbing that has not worn down yet. I think it is making the screeching sound. So, I think I'm good to go if I wait for it to wear down some more. I have to wonder if there's a disadvantage to having brand new wear rings with two ruts already cut in them. I'm getting 55 mph out of a 16 year old boat and I don't think I'm getting any cavitation so they must be working fine. Any other theories or advice is appreciated.

 

[LouDoo]

It sounds to me that you have a couple of out of spec. wear rings. I have used SBT delrin wear rings with no problems at all, however others on this forum have reported problems with the rings being out of tolerance. Can you post a picture so we can see how deep the groove is? Minor surface scrapes are O.K. but if you've cut deep grooves, IDK.

Lou

 

[Luke42_02]

I would guess the rut it carved out is 1-1.5 mm deep. It is a definate rut with a drop off, not just surface scraping. At original installation they rubbed so much that the starter could only turn 1/3 of a revolution before it stalled. They told me to lubricate with WD-40 and keep punching the starter. After 30-40 punches, the engines were able to fire. After 30 minutes out on the water at high speed, they now spin almost freely. The other factor in the equation is that the impellers are rebuilt by SBT. Only one of the 3 blades is currently rubbing and only at one spot on the ring.

I will post a picture tonight

 

[Guest_User]

a few things come to mind here. plastic pumps will distort if not tightened down properly and torqued to spec. most plastic pumps will have the impeller cut into the new wear ring regardless of which brand of wear ring. The only pumps that I`ve seen are totally true are the all aluminum with stainless wear rings... no cutting issues there.
seadoo`s and yamaha`s aluminum pumps are pretty dam good and solid... I wish there were alum pumps for our older boats...

now the key part that stands out are the SBT reman impellers... they absolutely can have different length blades. you`d be surprised the trash they get to rebuild and weld on to build up the blades again...

I suggest running new OEM`s or aftermarket Solas impellers... remember tho any aftermarket impeller will have a tighter tolerance than stock impellers, so you will have the aftermarket impeller cut in, but they are sharper and will do it quickly...

I would look at the impellers you have more closely for out of spec blade length, and watch the way to tighten down your plastic pumps.

 

[Luke42_02]

Ok, sorry for the wait, here are the pictures: