Carbon Seals - don't look past them!

[pincusa]

I've been enjoying my boat for some time now, but have been trying to chase down a large cavitation issue. I've rebuilt the pumps, changed the props, resealed the units to the boat, etc. As I had ruled out all the 'cheap' and easy stuff, I finally I decided to replace the carbon ring assemblies as some other members had mentioned it but I thought mine looked OK.

I ordered the HD assembly and new bellows from Dominic. While I had some technical problems with the units, Dominic was top notch for help/support. I will be using him again for future parts needs. I'd also recommend replacing the bellows as they are what's putting the pressure on the carbon ring. After 10 years of service, they weren't letting water in but had gotten hard.

The result? Amazing! The boat now shoots out of the hole. No more throttle up and listen to the engines rev while going no where! While cruising, there's no trail of aerated water behind the boat (Yes, the wake is still there ) Everything is just running the way it should now

I read many owners coming back with the same cavitation problems/questions. Please have a look at the carbon seals and think about replacing them. They might look OK and usable as mine did, but they're really just letting air in.

Hope this helps someone.

 

[rexsteiner]

its on my list to doo! :agree:

 

[Dr Honda]

Yep… My boat wouldn’t go past 10 mph when I first got it, and I changed the carbon seal, boot, and the stainless ring. Now the boat will do a solid 45mph with no sign of cavitation.

 

[scooper77515]

Mine are stock, as far as I know. But I picked up some cavitation last trip out, which I never felt before. Still hops out of the hole, but cavitated a little.

How do you tell if it is from the seal? How do you know when it is time to swap out the parts?

Getting a solid 45 mph, and getting there quickly, as per GPS. and pulls me up immediately with wakeboard, so not really concerned, but this cavitation last trip out has me thinking of an off-season project.

 

[shockerfd]

I couldn't pull a tube a couple of weeks ago. I found the clamps loose on my boot and the carbon ring loose. I moved the clip a notch and tightened things up and was able to pull a tube this past weekend. So there must be some truth to that area causing cavitation. I too plan on replacing some parts there over the winter along with a new wear ring/impeller.

 

[pincusa]

I wish I could tell you guys a way to see if they're worn out, but I too looked at mine several times and thought they looked OK. But here are some thoughts

• The SS collar on the drive shaft should be smooth. Any small ridge and air will get in.
• The new and old carbon rings looked the same so I'm honestly not sure if that needs to be replaced. But I didn't want to do the job twice, so I changed mine.
• The bellows - This is where I think the biggest change came from. The manual states that the bellows has to compress a certain distance, and my old one was still meeting that. But the difference between the old bellows and the new was over 1/2" when you put the two next to each other. I think the old one was just hard and compressed after 10 years and wasn't holding the carbon seal to the collar that well.

Oh, and keep any grease off the surfaces! The two surfaces should be grease free when you put them together.

This really has been the biggest change out of anything I've done to the boat.

 

[LSaupe]

It appears as if the boot acts as both a pressure boundary and a mating force between the Carbon Ring and Floating Ring (kinda like a rubber spring). Is this correct? As mentioned above the mating force could lessen as the rubber ages/hardens.

If so, any small leak in the boot could be disaster as well. Guess I never paid much attention to it but need to investigate this weekend and I have a ton of aeration, especially when under load.

Great info and thanks for posting this.

Larry S.

 

[pincusa]

Hi Larry -
Yes, that's correct. The boot is what's putting pressure on the ring to maintain contact. When accelerating, there's a considerable pressure difference between the two sides and if the contact force is weak, it's easier to pull air in than lift the heavy water.

You might try sliding the aft part of the boot forward and retighten the clamp in an attempt to apply more force to the seal. But this is only a temp fix

Let us know how it works out

 

[LSaupe]

Just looked at my carbon ring. Not quite what I was expecting, but maybe this is wore real bad. I have "significant" slop in one direction and it sits on a slight angle (relative to the stainless ring) leaving a small gap. Quite a bit of slop up and down (when standing directly over the engine) but very little side to side (like the bore is wore egg shaped).

My thought is that the slop should be the same (radially) (side to side on the shaft, perpendicular to the shaft centerline).

When these are new, it is a slip fit over the shaft or are these quite loose (carbon ring bore diameter to drive shaft diameter)?

I am amazed that this thing is able to seal at all the way it is.

I have a 97 Challenger. My positioning O ring is the 2nd position from the bow. By chance is there another one further aft?

Larry S.

 

[tony8a]

i am going to do in the winter! great info!
thanks!
:cheers:

 

[pincusa]

Just looked at my carbon ring. Not quite what I was expecting, but maybe this is wore real bad. I have "significant" slop in one direction and it sits on a slight angle (relative to the stainless ring) leaving a small gap. Quite a bit of slop up and down (when standing directly over the engine) but very little side to side (like the bore is wore egg shaped).

My thought is that the slop should be the same (radially) (side to side on the shaft, perpendicular to the shaft centerline).

Larry S.

Larry - If you're seeing the carbon ring at an angle to the collar, I'd think that you found your air leak!

You're correct that the movement should be the same in all directions. The center hole in the carbon ring is larger than the OD of the shaft and slides easily past. I don't think be design the carbon ring is ever supposed to come in contact with the shaft or be worn away by anything but the SS collar that it rides against.

You can slide the SS collar that the carbon ring rides on away to get a better view of both surfaces. Push the collar aft on the shaft and that will expose the 1/2 clip that holds it. Remove the clip and the collar will then be able to slide away from the carbon ring. Putting it back is the reverse
To remove the whole unit, the pump and drive shaft must be taken out.

 

[99SK04GTX]

Great thread, good information

And carbon seals are common to most doo's

 

[rembocanoe]

Ok I have NOT done this yet.. but while I was talking to a rep for an aftermarket impeller company... He said the best thing to do is get the 94-95 Drive line BEARING kit and replace the carbon kit. He said they only did away with the bearing cause no one would grease it and it needs to be greased every outing or so. Has anyone done this?
My question is the 94-95 shaft is smooth and not grooved so will the bearings ride ok? and miss the groove? My shaft is rusty and pitted anyways and I will probably replace it.

 

[ialonso]

Ok I have NOT done this yet.. but while I was talking to a rep for an aftermarket impeller company... He said the best thing to do is get the 94-95 Drive line BEARING kit and replace the carbon kit. He said they only did away with the bearing cause no one would grease it and it needs to be greased every outing or so. Has anyone done this?
My question is the 94-95 shaft is smooth and not grooved so will the bearings ride ok? and miss the groove? My shaft is rusty and pitted anyways and I will probably replace it.

I replaced my shaft seal with the Bearing kit. It is higher maintenance, they are to be lubed every 10 hours. have had them for a few years, and I have been happy with them. No air leaks. It makes removing the shaft and bearing kit very easy. I had a phase when I was blowing up the rubber boot at the PTO from over greasing, and having the bearing kit made replacing the boot much easier.

I stopped overgreasing the PTO, and I am not blowing up the rubber boots anymore.

 

[rembocanoe]

Well I ordered new bellows for my carbon seal to see if that is my problem with cavitation. I may go with the bearing kit in the future.. but currently finances are keeping me from fixing too much.

 

[rembocanoe]

Update.. found my cavitation. (again I'm new to the jetboat thing) while ordering a new impeller sells rep asked if I wanted the neoprene seal. Didn't know there was one.. as who ever worked on the pump before used sealant. He said the neoprene seal is the way to go.
And it seems to be working!

 

[bryckhaus]

I have a 98 speedster, I did the retrofit from carbon rings to bearing carriers with seals the trick is to cut the hose to put the seal right behind the groove about 1/8inch. When installing I put one turn of clear packing tape on the groove to not damage the seal. Also pack the bearing with grease before installing.

 

[my_nanc]

ok this has something to do with what i am doing i am replacing the boots and one of the pto drives it stripped out, now for the question, one of the motors is 1/2" closer to the pump/rear of boat than the other is this ok as long as it is aligned correctly? means that i will have different measurments on the boots pushing on the carbon joints.

 

[rembocanoe]

bryckhaus -
Which carrier did you use.. All I find are for ski models. No one references the jetboats.

 

[Dr Honda]

bryckhaus -
Which carrier did you use.. All I find are for ski models. No one references the jetboats.

They are the same. BUT... I don't recommend converting. If you ever have a bearing/seal issue... it will seize to the shaft, and rip the fitting out of the hull.... and... your boat will sink. When a carbon seal starts to fail... the worst thing it does is make cavitation. That's why seadoo stopped using the seal pack in '95.

 

[rembocanoe]

Update... Again the Neoprene seal worked great. I also did the change from carbon ring to bearing.. OMG Huge difference. I just keep a grease tube in the boat and shoot it every trip.. I know they say 10 hours but.. I like to be safe.. Also.. I did a pisser mod that I havent seen anyone do yet.. I took the pisser hose and ran it out a port near the drivers seat on the side of the boat.. now I can just look down and see the pisser working.. I don't know why they put it so low on the back.. you cant see it unless you stand up.. and the pisser is there to tell you the water is flowing in the engine.

 

[Dr Honda]

Yep.... the pisser is in a stupid palce on seadoo's.

We had a thread a while back on that. Here's mine.