17 replies to this topic

[tiggerman]

I'm currently trying out some custom bearing carriers and carbon bushings that were made by a member of jetboating.net . The carriers were machined from stock aluminum, and the bushings were machined from carbon stock. These parts will take the place of the carbon ring/ stainless steel ring assembly, or the greased bearing carrier that I have previously tried out. I have them installed, and have put about 3 hard hours on them so far. I haven't torn it back down to look at the carbon yet, but I expect all to be well. This modification is currently available for the Rotax boats, from the 580 engine thru the 800. This would go from '96 thru 2001 Speedsters, Sportsters, Challengers with the carbon ring type seal on the driveshafts, or the '95 models with the greased bearing carriers. It is expected to be a direct replacement for the ring setup, with nothing being changed so that you could not go back to stock parts very easily.
The modification on my boat eliminated ALL cavitation experienced on holeshot. You would be surprised.

[Bob86ZZ4]

I sure doo love that you have a similar boat to mine and are willing to experiment and post your findings here. This is the best SeaDoo site there is. The other day I turned a fellow Dooer (Challenger 1800 owner) on to it too. Let's hope he becomes a frequent user.

[tiggerman]

Very cool Bob! WE could always use more members, and would love to see you on a more regular basis . You were here before me, and made me feel right at home!
I love to try different things on my boat in search of the perfect setup. Granted, if it were a new boat, I would never consider these things. But it's not new, and I get a kick out of playing around and tweaking it. This little experiment, if all goes well, will be the best thing I have done to it. You would not believe the difference in the hook up out of the hole. You hit the throttles, and it is up and out just like that (snaps fingers). The only way I could make the boat cavitate yesterday was to get the intake up out of the water. I believe I have the setup now. One other thing I will do is experiment with pump wedges. I have some 3 degree wedges now, but am going to wait until after the carrier experiment is done.
Tell yer friend to come on! Keep on DOOin it!

[secord]

Tig:

i too am going to try the carbon bushings and bearing carriers. On the big board everyone seems to be completely satisfied with the results. What type of hose do I need to install them?

[tiggerman]

They should work with the stock hose for the '95. I got those from parkeryamaha.com for around $5 bucks apiece. OR, West Marine has the hardwall exhaust, 1 5/8" inside diameter for about $6 bucks a foot. You need about 2 3/4" for each side. Get a foot. I have pics of them installed, as soon as my wife gets home with my camera I will post them. The best part is ZERO, I mean ZERO cavitation.

[DownbeatDave]

Please forgive my ignorance, but why would there be cavitation with the stock rings, and why do these custom ones stop it? I don't think I've noticed this cavitation... Is it the same as getting the intake port out of the water in heavy chop?

[tiggerman]

They will cavitate by design. When the impeller pulls water thru, it creates negative pressure. That negative pressure will in turn pull against a hose that is "spring loaded" for lack of better terms. The hose will give and collapse some, allowing air to be sucked into the intake.
With the sealed carrier, regardless of whether it has needle bearings or a carbon bushing, there is no way around or through the carrier for air to travel. Each end is sealed with a double lip rubber seal, and the carrier is packed with grease/oil.
The impeller has no choice but to grab the water and go, unless of course there are other air leaks, the impeller is damaged, or there is excessive clearance between the impeller blades and the wear ring. It is the same principal as getting the intake out of the water. What happens when you do that?

[tiggerman]

18 hours on the carbon bushings and all is well. Port side carrier has gotten water inside, but who cares?! Starboard side has gotten no water in it. The port side rear seal is the culprit, and I'm sure I did it to myself. I blew the lip out once before I installed them in the boat by overfilling with grease. I pushed the lip back in, but forgot about the little steel spring that goes around that lip. I'm sure it popped off and isn't sealing now because of that. BUT, no worries, because water isn't going to hurt the carbon bushing at all. If it were the needle bearing, it may be a different story.

[tiggerman]

Anyone interested in a set of these carriers with carbon bushings, contact
labuhnj at yahoo.com---replace the at with @ .
They will fit any of the Seadoo boats with the 580 thru 800 Rotax engines.
Tell him I asked you to contact him.....

[monkeyseamonkeydoo]

Anyone interested in a set of these carriers with carbon bushings, contact
labuhnj at yahoo.com---replace the at with @ .
They will fit any of the Seadoo boats with the 580 thru 800 Rotax engines.
Tell him I asked you to contact him.....

so is this setup kinda like stock. i am have big cavitaiton problems and i think the culprit is the carbon rings. i replaced the wear ring and it didnt make it any better. i cant decide to replace the stock ones or go with the greased carriers or possibly this new way. also is there a tutorial on how to do any of these methods? i am very interested because i need to do something soon. thanks

[tiggerman]

Hey monkey.....that's the first thing I did too(wear rings), and they didn't help much at all. The next thing was the bearing carriers, they worked, but I wanted something different. Price out the stock vs. stock '95 parts needed, and they will cost about the same. J's custom carriers are a bit cheaper. They mount exactly as the 95 carriers do, the difference is the bushing and the design of the carrier. They are lubed with either grease or gear oil- the bearing carriers are lubed with grease.
I've got 20-21 hours on my custom jobs so far, and they are great. I have a lengthy tutorial pinned here on the Twin 85HP Rotax forum.
Two other things you can check before you do anything: move the bellows forward to force a better seal, then try it out. If it improves holeshot, then that's where your cavitation is.
Install the neoprene pump to pump support seal and try it out. If that helps too, then you had 2 problems. PM me and I will be glad to help all I can. Or post it here. Either way you decide to go, you're not going to be disappointed.

[Robmoo]

I wish I knew what you are all talking about. Is there a good manual for learning about and working on the pumps. I broke a shaft protector when I sucked a rope into my eninge yesterday. So come November I'd like to replace it. I'm wondering if there are some simple changes I can make to reduce cavitation while I'm replacing the shaft protector.

BTW Has anyone tried cuting the shaft protector so it only sticks out a 1/4 inch or so. If the protector hadn't been sticking out several inches into the pump tunnel I don't think the rope would have crushed it and caught on it.

[tiggerman]

I guess the best manual for this is the actual Seadoo service manual for your particular model boat. I'm going to get one soon myself....
As far as the shaft protector goes, both mine are sitting on top of my tool box
There are several posts hanging around where I describe some things to try to help reduce cavitation, like a neoprene seal around the pump to pump support.... doo a search...

[Robmoo]

I guess the best manual for this is the actual Seadoo service manual for your particular model boat. I'm going to get one soon myself....
As far as the shaft protector goes, both mine are sitting on top of my tool box
There are several posts hanging around where I describe some things to try to help reduce cavitation, like a neoprene seal around the pump to pump support.... doo a search...

I've seen several of the posts, but they are all Greek to me. I need tog et that manual so I can get a good idea of how the system works and what is where.

[tiggerman]

eBay- seller named fzr100 has the manuals on CD. Get the service manual for the jetboats, not the skis. He has quite a selection.

[Bob86ZZ4]

I bought the cd manual from him on ebay and it is very cool.

[tiggerman]

I bought the cd manual from him on ebay and it is very cool.

I got the owners manual from him when I first got the boat. I've been meaning to get the service manual, just haven't done it.

[tiggerman]

18 hours on the carbon bushings and all is well. Port side carrier has gotten water inside, but who cares?! Starboard side has gotten no water in it. The port side rear seal is the culprit, and I'm sure I did it to myself. I blew the lip out once before I installed them in the boat by overfilling with grease. I pushed the lip back in, but forgot about the little steel spring that goes around that lip. I'm sure it popped off and isn't sealing now because of that. BUT, no worries, because water isn't going to hurt the carbon bushing at all. If it were the needle bearing, it may be a different story.

Put 12 hours more and some hard riding the past 2 days on my carriers--No problems seen yet. Starboard carrier is still holding strong with no water in the carrier which means the seals are holding on. Port side still gets water inside, which is pushed out when greased. I have to say I'm quite satisfied with the results of this little experiment. As far as maintenance, I've gone 3 weekends now with nothing being done, except a squirt of grease to the port carrier. Total hours now: @40 +/- a few.. With these 40 hours, I should begin to see some wear on the carbon bushings I would think. I just need to tear it down and doo some measuring.....The shaft should be polished by now as well. We'll see.