I fell through ice into a pond the other day and my unit went to the bottom, rolled and then came up upside down. I have gotten all of the water out of the engine that I can find and the unit starts and runs smoothly. The problem is it will not accelerate. When I push the throttle it will spit or back fire and die. It starts right back up but no matter what I do it won't rev up. I changed, oil, oil filter, air filter and spark plug. Would really appreciate some help.