I'm pretty sure I had happen yesterday what cheezwhiz is describing. It is a horrible feeling. I ended up lassowing my boat like a runaway calf by throwing a rope in the water and running over it with the boat. When the rudder caught the rope I pulled her in and put my finger over the carb this killing the engine. I ordered a new block and gaskets immediately.

I am nuts about RC boats but I will NOT run if I can't get my boat to shut down via the TX. Please figure this out (it won't be hard) before you attempt to run again. Hemi and Cheezewhiz have you on the right track.