Speedster cavitation... what's left?

[Whister]

Wear rings, check. New rings with Skat Trak 14.5/22.5s. The new impellers were "scrape to fit" so the clearance is limited to the runout on the driveshaft.

Pump -to- ride shoe o-rings, check. Installed new ones when the jet pumps were off.

Ride shoe and ride plate seal -to- hull, check. Spent most of last week tearing all that s#!t off and sealing it all with 5 cans ($70) worth of "Right Stuff"

The seals on the driveshafts seem to be good .I havest changed them, but they don't leak, and choking up on the rubber accordian to apply more prssure on the seal whee it spins on the little metal hat acomplished nothing. . BEhind the boat it looks like it's blowing 7-UP out of the jets. Air is getting in somewhere.

The boat is driveable and still a little bit of fun to take out, but still cant pull a 60 pound kid out of the water on a wakeboard. Top speed is 48.5 MPH on glassy water (GPS) @ a tad over 7K RPMS

 

[kustomkarl]

It might be a help if we knew what seadoo you are talking about. You should include it in your avatar.

Karl

 

[robin savell lloyd]

I am realy sory about all the work you have done and still not got it right. I talked to dave at impros and he did tell me that you can suck air threw your threw hull seals and not leak water in your boat. I was not awhare of that. He allso confirmed that your new impellers are very good. Did you read this post that I had left in one of your old threads? I may be wrong but looking at photos in your other post it looks like you still have broken parts of your drive shaft shields. [the part that is supose to help keep ropes from being rapped around drive shaft.] I have read that when these break that they cause bad cavitation. You maybe able to remove them all to gether or cut them flush so they do not airiate the water going into pump. The drive shafts allso look rusted I would try and smooth them down a bit with sand paper. Good luck and I will keep looking into this for you :cheers:

 

[seadoosnipe]

The 1996 Speedster....

I had to look through some other post to find it Karl, but he has the 1996. Please include your info in your avatar so we don't have to go looking through the forum for your info.

Your getting good top end speed out of it. If your aerating, chances are, it's your thru hull seal. This is typical of the jet boats and some aerating is expected.

From your description, you seem to be getting what your suppose to be getting for a boat with twin 85 hp engines. The 717 isn't a speed demon.

As for pulling a 60 lb kid from the water on a wakeboard, that may not entirely be the boats fault. I posted earlier about the experience of the skier, being able to drag a boat or stand up on a board. These aren't propeller driven boats. They build their horsepower as the boat gains speed, by ramming water into the low pressure intake. So, if you got someone behind it, plowing the board, not able to step up, you may be blaming the wrong thing. I'm not saying this to push the blame elsewhere, just looking at the scenerio with an open mind.

I can sit in the water with my slalom on and when my wife stands on the throttle, I can use my weight (160) and ski, to keep the boat from gaining any momentum. But, if it starts moving, I can't hold it back. Drag created by a skier can be really bad on these boats until the skier either gains experience or is experienced from the get go.

I wonder if I can hold back the new 215 or 255 hp 4-TEC engines?:cheers:

 

[DiveMode]

Been out all last weekend wakeboarding with my speedster twin 85's... I weigh 195 (lost 5 lbs, yay!!) and I don't have a problem getting out of the water at all. 140cm board. I am needing a waketower though... having a hard time getting any good air. Boat goes 48mph with chop and will get 52mph or so on smooth H2O. Think I've got to change my port side wear ring though to pick up a few more mph's.

 

[seadoosnipe]

Great!....

Thats great!.........I should have waited for your reply. I have the 97 Challenger, 787 with the VTS, so the performance is a bit different.

But from what he says, it seems he's getting max horsepower from it. If he's aerating at all, that bad, he'd never get 48 mph...would you agree?

Also, it sounds like you've been doing this for a while. Would you say your experience in boarding has anything to do with the boats performance? Have you pulled someone who was learning and plowed the board a lot? Notice any difference in the boat?.........just curious.

 

[robin savell lloyd]

My single engine jet boat with alot less power would be able to pull a 60 lb wake boarder with out a problem.

 

[Whister]

Thanks for the replies! I'm going to try smooting out the jagged edges of the driveshaft shield (there's not much left at all though) and sliding some heat shrink tubing over them from the back to give it a smooth surface again. I don't have much hope in this... but I'll give it a shot.

The 60 lb kid I was just using as a reference. HE's a whiz behind an old 800 XP we have, but the Speedster can't accelerate fast enough

 

[DiveMode]

Snipe- the experience of the skier/boarder matters a TON! When I first started learning how to wakeboard ( & still am, no pro by any means) I was a freaking meat plow. My boat could pull your arms outta your shoulders if you didn't let go. Not a lot of difference in boat performance by any means from the experience of the person at the end of the tow rope... power is power is power. They either get up or they don't, depending on skill. Whister, I agree with Snipe... if your boat was cavitating/aerating that badly I don't see how you'ld get up to 48 mph. Are you jamming the throttles on your holeshots? I had to teach my girlfriend how to drive the boat... at first she couldn't figure out how to get me out of the H2O on the board. Idle till the rope doesn't have any slack... then a touch more throttle over the idle then jam it WOT untill it planes then back to 60% throttle so it doesn't go over 18-20mph. Gives a nice ride. Also, how long is the rope you're using? Shouldn't be over 50'. When I first started I was using a ski rope (there is a difference in ski/board ropes) that was 75'. BIIIGGG difference when I went down to the 50' airhead 4 section rope.
However, you may have a problem with your boat. It should yank you or anyone outta the water. What gets me is that your boat accelerates so slowly yet still reaches top speeds... it shouldn't be able to do that. Any thing else you can tell us about the performance of the boat at take off then at top speeds? Engine sounds? RPM's at low/high speeds?

-Greg

 

[dittrichw]

I have the same problem with my 97 challenger single engine. I have also done everthing you have done (new impeller, wear ring, & carbon seal). My boat will top out at over 50 MPH on boat speedometer, but takes forever to plane out. I can not pull a water skier out of the water. Could this have anything to do with an exhust leak? The engine makes a different sound until it plains out, like something is spinning more free until it plains out. I hope we can get this problem fixed.

 

[Whister]

Dive mode- I appreciate the heads up! It's definately cavitating though. You apply more than half throttle from a start... the boat starts to accelerate, then the RPMS peg the limiter, it blows 7-UP out the jets.. and the boat falls back in the water. Ease back into it slowly... once it gets up on plane you can hammer it and it takes off pretty well.

It's sensitive to weight. With just me in it I can apply more throttle before it cavitates. With four people it takes a while to get on plane. LAst weekend we had four of us in the boat, and we slowed to pick up another jetskier who had fallen from her ski (she was probably 180) and it would not get up on plane to save it's life.