I have a 1971 Evinrude SkiTwin on my 1971 Kingfisher skiff. The other day, I was pacing a friend to see what kind of speed he could muster (my fishfinder has GPS) I ran full speed till I caught up with him and then throttled back to hold his speed. About 3 seconds after throttling back, the engine went to FULL rpm!! I cut the throttle and it came down some. I cut the key off and it didn't stop! I moved the key back and forth... Still running! I snatched the fuel line off and it ran for about 20 seconds. I checked and the prop was still there and felt still connected. I restarted the engine and it ran normally, except no forward or reverse... I got it home and pulled the foot.. The top of the driveshaft was smooth as a baby's butt. I looked up into the leg of the motor and the driveshaft socket looks to be fine... Anyone ever seen this happen? Cause? I didn't strike anything in the water and was in about 50ft, so no hitting bottom. Maybe one of things that just happens... Anything that could have been damamged thatI need to look for before I plunk down $200 to fix a 40yr old motor? Been thinking of repowering with a 70's-80's through prop type 40-55hp, but cannot find one that I can afford that looks like it is worth buying. Plus, I would have to redo the controls AND upgrade the streering. Mine has old pully style... ALOT more money than I have right now... Maybe next year.