787 wear ring and clearance issues

[nisjeep]

I recently replaced both wear rings and neoprene seals on my 99 Challanger as a matter of course during yearly maintenance. Now the boat has developed cavitation problems...

2 years ago I replaced them aswell and the impellers had almost no squish to wear ring. This time the clearance were just just in limits.

My questions are : Do you get 2 wear ring sizes like 140mm and 139.5mm?
Are the impellers (oem) maybe worn smaller?
Or are my pumps now so effecient that that they are sucking through the carbon rings?
Lastly the neoprene seals are protruding slightly in the pump channel, maybe thats causing turbulence before the pump?

Anybody had this problem on a basically new fitment yet?

 

[mikidymac]

There are only two wear ring sizes, the 140mm and 155mm and this depends on your pump. Aftermarket ones can have bad tolerances and cause issues but as your impellers wear they get smaller increasing the clearance too.

There is no reason you should be replacing the rings every year or two unless you are constantly running your boat through sand and rocks and if you are STOP doing that!.

If you have the 155mm pump there is no neoprene seal.

 

[nisjeep]

Thanks for the reply. It must be the aftermarket rings then. Serves me.right for going on the cheap.
I generally watch and maintain the boat to a "t".
However I got stuck on a tidal river bank last year with a load of kids on an outing. So I pumped mud for an hour or so to get out.
Must have knackered it there.

 

[Matt Braley]

If the pump parts look good when you pull them back off then the neoprene ring may have been sucked in. You can get a good seal with a little 100% silicone but it makes the pumps harder to pull in the future.

 

[Rossterman]

Talk to nick at osdmarine. He sells a high quality delrin aftermarket ring that will give very tight clearances (some have had to turn the shaft by hand and allow the impeller to cut the required clearance inthe ring. Works perfect!

 

[nisjeep]

Thanks ,but I am down in Sunny South Africa !

 

[nisjeep]

Matt , I have pulled the pumps again and the neoprene was busted in several places. I siliconed them back in,dropped the weedless gates an smoothed it over with my finger.

I am going out on Sunday again, let us see.
Cheers

 

[Rossterman]

Silicone can work good if neoprene is gone. If the ring is damaged or clearance is too large you’ll still have cavitation issues (not nearly as bad as with a leaking neoprene seal though). I’d still drop nick an email even though your location. He may have some leads as to where to go for a similar part in your neck of the woods. You can also just buy the factory rubber one from the dealer and replace it if the impeller isn’t too worn on the edges. They are SS so water won’t wear them out (but running sand through the pump will). Eventually age causes the rubber ones to fail. Ask me how I know...

 

[nisjeep]

Update. Problems solved. So it turned out to be the neoprene seals. Topped out at 46 mph with wifey and 2 sons onboard. I am one happy camper !

 

[Matt Braley]

Awesome.