2006 stx 15f runs awful in the water but amazing out

[johnny89345]

Like the title says my*ski*runs*amazing until i put it in the water then it doesnt want to rev up past like 3k rpma or go past 20-25 mph but the second i take it out of the water it runs great again and revs to redline. Compressions good, fuel pressures*set at 43 psi and doesnt move during any throttle condition, fuel and filters are both brand new, and new ngk plugs, brand new batterey. please help me i dont know where to start

[RLACEMAN]

Try this, hook up a hose to the flushing port under the hood, have a valve on the hose very close by, start engine & then turn on the water, does the motor start to sputter? Turn off water & engine starts running better if all works this way you most likely have a head gasket allowing water into the combustion chamber, but it is bad in a spot that doesn't affect compression readings, or worse a cracked cylinder head. Was there any water in the hull after you put it in the water, another slim possibility is a leaking hose that sprays water around & it gets into the air intake.

[CJ River Rider]

Before you worry about head gaskets or cracked cylinder heads, check your blue coupler between the exhaust manifold and first waterbox. I had the same symptoms as you a couple of years ago and had a leaking coupler. I was skeptical that this was causing it but when I replaced it, all was back to normal on my 08 15F. An exhaust leak will kill you.

[johnny89345]

I replaced that coupler last year with a thicker one from a local race shop. Could it be possible upon reassembley i hooked some hoses up wrong? Does any one have a pic of how the hoses should be routed

[grumpy_steven]

Try riding with the seat off. An exhaust leak with stop your ski dead in its tracks. With the seat removed, the ski will get enough air to run full speed and you'll be able to see the leak.

[johnny89345]

On the land it runs 100% meaning with the hose hooked up and running. But i may have just gotten a lead tell me if im wrong but i just pulled the pump and its worn pretty bad. Looks like its been sanded down. And the props a little chewed up

[johnny89345]

Well today i went over all sensors and possibilities to track down my problem. Besides my prop being a little chewed i doubt thats the issue.
Compression is 210psi on all 4 cylinders
Exhaust temp sensor 161.1k ohm at 88° and 195k ohms at 78°
Cam sensor 439.1 ohms
Oil temp sensor 168.6k ohms at 88° and 195k ohms at 78°
Sensor at front of motor blue/green wire .539k ohms

Ohmed all 4 spark plug wires and found one to be bad cutting in and out when i grabbed it showing 0 ohms of resistance to some unbelievably higher number

[johnny89345]

Okay so i changed the plug wire today and it literally made no difference whats next?

[GlenT]

Pull the pump and check for damage on the splines for both the drive shaft and the mating splines in the nose of the impellor. While your at it, pull the flow cone off the back of the pump and check for water intrusion.

[johnny89345]

The splines are fine, no play and the prop spins free and smooth.