2-stroke PWC Bogging down.
 

Hi all,

2004 Yamaha Waverunner XLT1200. 3 cyl 2-stroke. New plugs, fresh mid-grade gas. Starts and runs fine. All 3 cylinders have ~100psi (almost no deviation) in a compression test. Headed out on the lake the other day. Ski took off - hit 45mph quickly. Within about 250 yards or so, motor bogged right down and sounded like it was running in mud. Top speed dropped to 35mph wide open. Tested sparks - all 3 plugs sparking. Not really that wet, but a bit. Black tips.

Specs attached.

So, is the mixture too rich? Seems odd that it runs well, then bogs down. Wouldn't the mixture be the same no matter what?

Clogged fuel lines? Seems like that would also be a constant problem.

Winterizer oils stuck in the carb?

I'm sure I will be chasing these, but I'm hoping to start down the right path first.

Have you checked to see if you didn't suck anything into the water impellor under the ski. There is a screen there that can be removed. We had issues last year when grandkids sucked a few rocks in when they were in shallow depth.

Dirty carb or fuel filter. If it has a choke, get it up to 45, wide open, and pull the choke for like 5 or so seconds, then open the choke and let it rev up again. Repeat a couple times, you may pull the crap through the jets.

Otherwise you have to pull it apart and clean it.

Don't blow yourself up.

sounds like bad gas if you are getting spark, or possibly like of air.
I would run a bottle of seafoam through it first before anything else

Thought
 

I don't know if this is your problem, but:

I have a 1996 GTX and it showed similar issues. What I discovered is that the fuel lines that the manufacturer used were type B. The ethanol added to our gasoline had degraded the fuel lines and the interior of the lines was sluffing off and clogging the carbs.

We ended up replacing the fuel lines and the fuel selector switch, rebuilding the carbs and cleaning out the gas tank.

Jetskier :cool:

A bog like that usually means a lean mixture. I am with jetskier, I think you have fuel starvation issues. Don't run it like that until you address the problem or you might have issues that are far worse.