96 Speedster--Carbon seal

[GrampaBigJohn]

I have an ongoing cavitation problem, even with new impellers and wear rings.
How do I check the carbon seal? Is it under the bellows? Can I peel the bellows back? Thanks, blackwellchris, for helping me find the parts schematic...

GrampaBigJohn

 

[ski33]

I have an ongoing cavitation problem, even with new impellers and wear rings.
How do I check the carbon seal? Is it under the bellows? Can I peel the bellows back? Thanks, blackwellchris, for helping me find the parts schematic...

GrampaBigJohn

i cant see it being the carbon seal ,this is just to stop the water from entering the hull from where the shaft enters the engine bay.
check you have the right clearance between the impellor and ring !
some pics of the pump might help and more of a description of the cavitation.

 

[Dr Honda]

i cant see it being the carbon seal ,this is just to stop the water from entering the hull from where the shaft enters the engine bay.
check you have the right clearance between the impellor and ring !
some pics of the pump might help and more of a description of the cavitation.

WHAT!!!! A bad carbon ring will make the boat cavitate so bad, it won’t go more than 10 mph.

It’s hard to check it in the boat. I had a ring that looked OK… but once I took it out, I could see how bad it was. You will need to pull the drive shaft to get it out, and get a good look at it. One thing you can do… loosen the rear clamp on the boot… push up on it, so there is more pressure on the seal… then retighten it. Doing that may get you a few more trips out before you have to replace it.

Good luck

 

[GrampaBigJohn]

96 speedster cavitation and carbon seal

If the carbon seal is the black thingy right before the bellows they are loose enuf that I can wiggle them. Will pushing the bellows forward help>

GBJ

 

[99SK04GTX]

The carbon seal is enclosed in the rubber accordion sleeve

You cannot see it with the bellows in place.
The carbon seal is your shaft seal. it is where you have bilge on one side and lake on the other. If it is allowing air to pass it will cause cavitation.
The bellows works like a spring to put light pressure pushing on the carbon seal. How much pressure is what they call the pre-load. If your RPM's are good, impeller and wear ring good then cavitation is probably due to carbon seal.
Remember though, just a small piece of trash in the pump can cause the same problem.

 

[ski33]

WHAT!!!! A bad carbon ring will make the boat cavitate so bad, it won’t go more than 10 mph.

It’s hard to check it in the boat. I had a ring that looked OK… but once I took it out, I could see how bad it was. You will need to pull the drive shaft to get it out, and get a good look at it. One thing you can do… loosen the rear clamp on the boot… push up on it, so there is more pressure on the seal… then retighten it. Doing that may get you a few more trips out before you have to replace it.

Good luck

ive just had the carbon seal and bushes changed on my boat and they where bad ,so bad it was takeing on water but no cavitation whatsoever !the carbon seal was all scrached and the meatal bearing part it pushes was all black and pitted .

 

[swill777]

You need to check the pressure between the carbon-ring, and the carbon ring carrier (or they call it the carbon ring collar)... the piece of stainless steel that actually touches the carbon ring. if there isn't enough pressure there, water will leak through there, and/or air will suck through there, and YOU WILL have MAJOR cavitation. Instead of buying a new one, I just loosened the clamp on the hull side, and pushed the boot down toward the PTO (engine) side, to put more pressure on it and just tightened the clamp. Works for now, but that side DEF needs a new carbon ring.. it's worn for sure. It even eventually got loose, starting cavitating again, and I had to re-tighten it after about 6 months. A quick tightening can get you buy for now til you get one.