I have a 1992 150HP Mercury outboard that was sitting for a little over a year. I took it out today and it cranked right up. I idled aroung for a little while waiting for my trailer man to get to the courtesy dock. Picked him up and heading out. Trimmed the motor down and push full throttle. Away we went. Boat plained out and we were cruising. About 30 seconds in it kicked out of gear. The engine was rev'd but no movement. I immediately threw it into neurtal. When I put it back in gear at an idle it was fine. Anything past that the engine just rev'd. Reverse works fine. How much damage do I probably have? And what is probably wrong?