Just took my (used) new toy for it's first sea trial. Engines started fine, shifter worked well. The port throttle lever needs tightening because it slipes back to idil on it's on.
The real issue is at about 4000 rpm' the engines speed up to 7-8000rpm with no power. I assume this is cavitation (new to jet boats). I can achieve about 20mph before I loose power trying to go faster. Any ideas before I call the dealer. I can repair most things so would like to if I can.
Thanks in Advance!
Jet On!
Mike

1996 Speedster
Started by alltexan, Nov 27 2003 03:04 PM
4 replies to this topic
#1
Posted 27 November 2003 - 03:04 PM
#2
Posted 30 November 2003 - 08:42 PM
What about weeds? That's sometimes what happens to me when I get weeds blocking my intake. Otherwise I would check the wear rings. I don't know if there is an easier way to do this but here's how I know for sure you can check them. Take off the back parts of the jet drive nozzles until you get to where you can see the impeller. Then look at the black part that surrounds the impeller. This should fit pretty close to the edges of the impeller. That's what makes the seal so the impeller makes thrust. This part is replaceable so the new ones will make good seal. I don't know if a worn wear ring would cause the symptom you describe or not. Anybody else know?
#3
Posted 01 December 2003 - 06:32 AM
Thanks... I checked the clearance,impeller to wear ring, and it is within tolearnce <.040". You can also check this by taking off the intake grates. The impellers were in good shape... no obstructions. The troubleshooting section in the shop manual also says ventallation can be caused by air entering through the impeller drive shaft from the engine compartment. This would mean a faulty O-ring or seal.
Anyone noticed that issue before?
Jet On!
Anyone noticed that issue before?
Jet On!
#4
Posted 01 December 2003 - 09:00 PM
Wouldn't water come into the bilge then through that faulty seal? If you are sitting still in the water that is.
#5
Posted 09 March 2004 - 12:42 PM
Not necessarily... The seal around the drive shaft is actually made up of two pieces. A stainless steel plate fixed on the driveshaft and a carbon ring mounted in a rubber "boot". The mating surface of these two parts is where water can leak into the boat, OR, when running, air can be sucked in by the impeller because of the pressure differences created under the boat when the impeller is turning. Water may or may not leak in while the boat is not running. I have had to "adjust" the tension on the seal surfaces to stop water entering the boat, and as a consequence, this greatly decreased if not stopped, the air entering from this point. Confused yet? There are many things that can cause the pump to cavitate. Worn out wear rings (hence the name) from sucking in ANYTHING but water (ski ropes, weeds, sand, etc..) sharp edges in the path of the water traveling to the leading edge of the impeller, or the impeller itself with a damaged blade. Anything that blocks the smooth flow of water will (may) cause the pump to cavitate.Wouldn't water come into the bilge then through that faulty seal? If you are sitting still in the water that is.
1997 Seadoo XP 800 (sorry, at least it is a DOO!!!)
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