Sea doo challenger 1800 1998 high rpm-no speed

[alsen]

I have a seadoo 1998 Seadoo Challenger 1800 and I've had it out on the water a few times this year. I have several issues with the boat and need direction as follows: i. On the port engine if I apply full throttle to both engines the RPM consistently increase (and the boat accellerates) till about 4500 RPM at which point the RPM on the port engine jumps to over 7000 RPM almost instantly and makes a high pitch spinning sound almost like its spinning in air. I also loose thrust at that time. Is this what cavitation is? If not what does this issue sound like? Furhtermore - if instead of applying full throttle I do the same thing but gradually as the speed of the boat increases I can get the RPM to almost 5500 before the same problem occurs. ii. Can the issue noted above be caused by an imbalance in power output? iii. On this particular model is there a seal between the jet pump and the hull? I can not find one on the parts diagram for this boat and i've confirmed in my boat there is infact no seal but that seems odd to me. iv. What test should I undertake to narrow down as to what the problem is? Either on-land tests/inspections or in-water tests to determine where this issue is originating.

 

[Coastiejoe]

There is a Carbon Seal on the drive shaft. If it is worn it can suck air and cause impeller slippage. If the wear ring is worn and the gap from the impeller to the ring is the width of a dime or greater the ring needs replaced.


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[jhjesse]

Yes Cavitation.
How long have you owned the boat and do you know if the jet pumps have ever been serviced?
As Coastie mentioned you probably need to replace the carbon seal at a minimum. Should replace the bellows as well.

 

[alsen]

Hi I have just have the boat 2 weeks. I have change carbon seal, bellows, new solas impellers, wear rings, alignment engine, needle bearings and oil in jets...

 

[Coastiejoe]

I would still look at the gap. If any were not made to specks or you sucked in debris is all it takes.


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[jhjesse]

Did you install new neoprene seals when you reinstalled the jet pumps?
http://www.shopsbt.com/sea-1998-dch1800/sea-doo-wear-ring-gt-xp-gts-gtx-spi-spx-271000290.html

Try this:
loosen the bellows where it clamps onto the thru hull fitting and move the bellows forward creating a tighter seal on the carbon seal, then install a cable tie behind the bellows onto the thru hull fitting to prevent the bellows from sliding back.
Also maybe apply some grease to the face of the carbon seal to see if it makes a temporary seal.

 

[howie099]

You bought all new seadoo parts for carbone seal? Not after market ones? The new ones that OSD sells have a thicker seal carrier and there boot is the newer longer OEM one that that is like 1/4" longer than the one that came with the boat. If you got an aftermarket boot and you can push it back real easy that is bad you will suck in air. If you have the drive shaft with 3 grooves go to a different groove to make the boot stiffer. That seal on the pump you can get is just one for 140mm pump most parts site just list it as that. The boats never came with them. You can add for extra measure.

 

[alsen]

Thanks guys! I will order a new neoprene seal and try the other tips.