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99 Speedster SK cavitating...

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seadoobie

seadoobie

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I recently bought a 99 Speedster SK...We did a on water test for about 30-45 mins before I bought it & brought it home & it ran fine. On saturday I took it out on the river for a bit, then after a good run it seemed to have lost all power & the engines were running fine. I was able to get it back to the dock but could only manage to get 8-10mph out of it before it would loose power again and the engines would just rev.
I'm not real sure where to start here since it didnt come with a manual, but I was told by a few ppl that it most likely sucked up something in the water and thats the cause of the cavitation since it happened all of a sudden. So where do I begin on getting this fixed?
Any advice much appreciated!!
 
Also look into the impellers from the rear. Your SK should have the seedless system on it??.. The handle on drivers side under the steering wheel.
 
ROPE!...rope was wound around one of the shafts. Also it does have the weedless system on it. The props looked a lil dinged up on the intake side and I'm now wondering how much of a problem they will be...dunno if it was from this incident or from before I bought it. I also looked at one of the engine tags and it says it has 718 cc engines...what kind of power do these make?
 
The SK's run 85 hp each. The red speedsters run 110 each.
Congrats on your first fix. !!
The impellers(props) run 25$ each thru SBT with exchange. If those are dinged then order new wear rings also. It's a maintenance item. Also the impeller removal tool (15$).
It's the best investment and cheap to ensure getting on plane fast.
Do a test run first, if your happy with take off and plane time then go with it.
 
Nice! thx for the great advice! I am sending the seats in to have them recoverd this week...so I think I'll take the time and redo these props & wear rings as well. I also read somewhere today if thes props vibrate enuff it can cause other damage too. A ounce of prevention is a pound of cure in this case I gather.
 
Might as well. Plenty of threads on how to replace (ahem) impellers...
Since they will be off.. Do a pump rebuild also. Super easy.
Welcome to seadoo'ing 101. :)
 
Yeah that is an easy fix. A lot of times though once you clear the rope you are good to go again. I would try it out before you tear it all apart. Also the SBT impellers exchange has gone up to like 60 something bucks each. Not so good of a bargain anymore.
 
I think I'll post some pics of what those impellers look like first & get some more feed back before tearing them down. I suspect I'll have to fix them though. Also when is the best times to use the weedless system on the river? I mean besides in the weeds...should I run with them down to keep the intake clear?
 
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Well the pics I took didnt really show what I was talking about...they were blurry. I guess I could get a shop light under there & try to get some good pics this evening so I could get a judgement call from yall. So I'm not sure if there ok or not at this point, but the impellers do have a few dings around the outer edges,ect. So whats the best way to examine them to make a decision here? Also would better intake grates help keep stuff out there as well?
 
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No. The weedless stays up until you need it. I've never even used mine. Not sure how good they actually work.
 
99 Speedster SK cavitating...redux

So heres the impeller pics:
Impeller_port.JPGImpellar_port 2.JPGImpeller_starboard.JPGImpeller_starboard 2.JPG

Thes are the best I could get atm..hopefully someone could lemme know what they think
and if i need to replace them or not. Any input welcome! Thx!
 
Yeah it doesnt look bad from the back side. Looks like there mainly damaged on the intake side from what I can see. I was hopin they would at least get me through this summer & overhaul them durring the winter. So I'm guessing a call to SBT is in order here.
 
Yeah the impeller in the first 2 pics looks like it has a bent blade. The other one looks rough and needs refurbed. I would throw in 2 rings and refurb the impellers. About $220 and you will be haling a$$ again.
 
Phildoo said:
The SK's run 85 hp each. The red speedsters run 110 each.
Congrats on your first fix. !!
The impellers(props) run 25$ each thru SBT with exchange. If those are dinged then order new wear rings also. It's a maintenance item. Also the impeller removal tool (15$).
It's the best investment and cheap to ensure getting on plane fast.
Do a test run first, if your happy with take off and plane time then go with it.
Click to expand...

I have a 99 Red Sppeedster sk and the engine size was an option, either 717's (85hp@7000rpm) or 787's(110hp@7200rpm)

Mine is the 717's


Couple Gotcha's:
On the weedless system, you only use that with the engines stopped according to the manual.
Also according to the manual when you use the water flush adapters under the engine cowl, you need to pinch off one of the water lines if you want to run the engine and get cooling to work properly.
 
What is cavitating? I can't figure it out. I've seen this in a few threads now, but I'm still stumped. Leaning to one side? Directionality?
 
To really understand how a Sea Doo works, you need to understand the basic propulsion concept. Think of your ski as a giant pump. The engine turns a drive shaft with an impeller. As the impeller turns it sucks water in through the intake on the bottom of the watercraft. The impeller is sitting inside the wear ring. It is almost a water tight fight. It should be very snug. As it sucks the water up, it pushes it out tha back side of the impeller. The water is forced through a smaller opening in the nozzle. Since the nozzle has a smaller opening, it creates thrust as the water is pushed out.

Anywhere along the way, if the water finds less resistance, it will escape there and in turn you will lose the amount of thrust out the nozzle. So if you have more space between the wear ring and the impeller, the water will be forced out around the imepller instead of pushed out the rear. That is what we refer to as cavitation. You need the same amount of water to go out the back as what comes in the intake.

Think of taking a straw and blowing as hard as you can. Now take the same straw and poke some holes in it and blow again. You get a lot less air out of the end now.....same concept. It only takes a slight leak to really affect your performance.
 
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