I have a 1990 Yamaha 150 2 stroke motor. Every once in a while, when I am putting the throttle in forward, the throttle is very hard and feels like it is sticking. Going into forward and going into neutral it will happen. Reverse has no issue. A month ago, we were helping out in a regatta, as I was putting the throttle in forward the neutral throttle lever actually came up and reved the engine. It then slipped into forward slamming the engine into forward. Anyone have any ideas what my issue is? Thanks for any help.