Anybody else have this problem?

I recently set timing on my 89 Sunsport PCM 5.8L. I set it to 12 degrees base. It runs much better now (was in the neighborhood of 20 degrees before), but I am encountering a new problem since adjustment. After pulling someone on a tube or board, the RPM's hang at ~2000rpm and will not drop to idle speed. Obviously, the boat won't come out of gear at that speed. If I turn the boat off and fire it back up, it runs at 700rpm idle speed.

What could be causing the rpm's to hang out up there? Engine has a Holley 650cfm carb on it, but the fact that it returns to normal after shutting down leads me to suspect something electrical? Any ideas are welcomed, thanks!