High rev in neutral

[cgardner007]

I just purchased a Suzuki 2.5HP engine to use with our inflatable dinghy. Last week we used it for the first time, and all was well. Several days later we put the boat in the water, it started on the first pull, I let it warm up for about 5 minutes and then we operated it forward for about 30 minutes. I shifted the boat from forward to neutral to stop and noticed the engine imediately revel up without the throttle being turned. I shifted it back into forward and it idled normally. I ran the engine for another 15 minutes to get back to the dock. At the dock the same problem persisted. Normal RPMs and throttle control in forward and it revs up on its own in neutral.

This is a brand new engine with brand new fuel. Any suggestions would be greatly appreciated.

[Hoosmatroos]

These engines are set very lean from factory. Is it possible to adjust the mixture screw or is it blocked?