I had it happen on my Outback DD just last week. I was taking kids from Camp Kemo tubing. It has never happened kneeboarding or skiing. We kneeboard with a few people and about 1000 pounds of ballast.

While turning with tubers in tow, it reved high enough to shut the engine off. Did not experience this but once so I wrote it off as cavatation. No other problems or experiences with it so no big deal, hopefully you wont notice it again.