Did you ever figure this problem out?
Just looking for a similar problem to my ski, did you ever figure this out.
Mine is doing the same thing. here is what i think is happening.
I had the heads off mine and installed new o-rings, i think i pinched an o-ring and when the ski in in the water, it pumps water into one of the cylinders and kills one of plugs with water.
After i put it back on the trailer, it straightens out after 10-20 seconds of running and then runs great.