No thrust suddenly, carbon ring failure?

[MxRacer965]

Hi all,

Could use some feedback. Ski is a 2000 GTI, 717 and suddenly lost 98% of its thrust.

I was on it with a couple children, the young lady that was driving in front of me was WOT and then shut off entirely, then got back on the gas. When she got back on the gas the engine revved to the limiter, and we got almost no thrust, just a lot of bubbling/cavitation.

I had noticed the day before there was quite a bit of water in the hull, but I didn’t see anything leaking. Skip ahead to when I lost all thrust and when I took the seat off I noticed water leaking in between the carbon seal and the ring it seals against. I tried to start the ski but it didn’t want to turn over, so I assumed something in the drive line bound up...not remembering everything that makes up the drive line I figured a bearing or something initially, no concern the engine seized.

I put the ski on my lift and started researching and instantly came across the carbon ring as a possible culprit. It also had no problem turning over and starting again. When it started I did hear a squeal from the drive line somewhere.

Today I did a little more checking. Put the ski in the water...no leak. Started it up and still just revved and no thrust. I pulled the seat while on the water and compressed the bellows towards the back of the ski and water poured into the hull, but would stop when I let the bellows extend. I then noticed I can very easily compress the bellows a good 1/4”-3/8” with no effort. I had my wife grab the PTO and rotate while I inspected the impeller and it did rotate back and forth.

So...given how easy it was to compress the bellows would it be logical to assume it is sucking in air and causing cavitation? Replace bellows, carbon seal, and ring before anything else? Does it make sense that it would fail so suddenly like it did?

Thanks in advance!

Aaron

 

[AKnarrowback]

Did you look at your impeller yet? See if you sucked a stick or something into the pump and wrapped it on the impeller leading edge.

 

[MxRacer965]

I just had my cell for a flashlight and I honestly didn’t look too hard for foreign objects, I mainly just wanted to see that it rotated when the driveshaft did. I can’t really get under it to check the intake, it’s in the water on a lift and the water temps have dropped to around 65 so I’m not about to get in! [emoji23]

I’ll check closer with a decent flashlight that I can stick in further and inspect more closely. I don’t suspect anything is in there though, the lake is pretty clean and doesn’t have much in the way off stuff that can get sucked up there but of course it’s a possibility.

In doing some research it seems the metal ring can be held in place via a metal C clip, or with a o-ring. I wonder if mine had an o-ring that failed and allowed the ring to travel towards the engine, reducing the ability for the carbon ring to seal properly?

 

[POPPS]

I would check the wear ring carefully, a leaking carbon seal will not take away the amount of thrust you are describing.

 

[MxRacer965]

Checked and it doesn’t appear anything is obstructing the impeller leading edge.

But would the wear ring instantly result in almost zero thrust after we were just cruising at WOT with the speedo reading 45-50? I had read the thread below, which turned me on to the carbon seal.

engine revs high with no thrust

 

[mikidymac]

The old wearings are known to blow apart and cause instant cavitation.

 

[POPPS]

To be absolutely sure, just pull the pump, and then you can inspect the entire wear ring and prop in the palm of your hands.

 

[MxRacer965]

Never knew they were potentially prone to breaking apart. I guess if it did fail that might make it easier to remove at least! [emoji23]

I’m going to dig into it next week, I’m heading out of town for work this week. I may just order parts to rebuild the entire pump and do the carbon seal while I’m in there. That way it should hopefully be all set and I don’t have any down time next summer. I live in MI so we don’t get a lot of boating time so I need to make the most of it while I can!

Anything specific to worry about regarding alignment of parts? Any shims I need to be looking out for? Seals for the jet pump to hull?

Looks pretty straight forward from the little bit I’ve looked. 6 bolts to get the nozzle off and 4 for the pump itself. Impeller tool, a hydraulic press for special tools...

Missing anything?

 

[mikidymac]

All you should need is the wear ring and a pump cone o-ring to change the oil.

 

[MxRacer965]

Understood, but while I’m in there I may just rebuild everything. I have no idea the maintenance history other than the past couple years that I’ve owned it. And when I changed the pump oil the first time it was mostly/all water. [emoji51]

 

[mikidymac]

Make sure you set the bearing depth per the manual, you can't just push them in and guess.

 

[MxRacer965]

If I recall the manual states to use a special tool to seat them the proper depth. Absent that too can I not just measure the depth and ensure I press them in the same distance? Or is there an actual spec out there I can reference?

 

[mikidymac]

The manual lists the distance so I just use a digital caliper.

 

[PorknBeans]

Is Dr. Honda still making those seal/bearing tools? Those tools are the bomb! He made me a set of them and they are like gold to me!

Here are the pump rebuild pages from the manual:

 

[mikidymac]

No, Dr. Honda is dealing with other things for now.

 

[MxRacer965]

Well I took the pump off today and the problems are pretty obvious. The wear ring looked like a cheese grater, the shaft the impeller mounts to is in two pieces, the thrust bearing exploded, one of the other bearings exploded, and the nose cone was melted internally. When I pulled the pump off the impeller partially pulled out of the pump housing...



I had planned to rebuild it even if it turned out to look OK, guess it’s a requirement now!

Going to do carbon seal and bellows while I’m in there.

I changed the oil each of the seasons ive owned it, must have gotten a leak...

 

[jimmyluke]

Well I took the pump off today and the problems are pretty obvious. The wear ring looked like a cheese grater, the shaft the impeller mounts to is in two pieces, the thrust bearing exploded, one of the other bearings exploded, and the nose cone was melted internally. When I pulled the pump off the impeller partially pulled out of the pump housing...

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I had planned to rebuild it even if it turned out to look OK, guess it’s a requirement now!

Going to do carbon seal and bellows while I’m in there.

I changed the oil each of the seasons ive owned it, must have gotten a leak...

Probably a good idea to pressure check the pump as per the manual after rebuilding and also after changing the oil.

 

[MxRacer965]

New vs old



Looks like the seal on the impeller side failed, it was super brittle.

Bearings (what was left of them) are out, seal is out, wear ring is out, ready to reassemble! New bearings are in a chest freezer now so hopefully they go in relatively easily.

Just need new carbon seal and bellows and it will be ready to water test before the leaves start to fall...