slipped connection
This is not an uncommon issue especially if the motor experienced a quick shift through neutral at higher than idle speed. There is a connecting rod that runs down the inside of the leg to the gearcase. This connecting rod is in two parts joined with a linkage that typically is friction fit with a couple of nuts. There is an access plate on the side of the leg about an inch and a half round. Remove this plate, (usually held in place with a couple of small bolts) to get at the linkage. Once open you can see the linkage, loosen the nuts and readjust them. (You will likley see the wear marks of where the rods should be).It is easiest to do this job with the motor off the boat, lying on its side with the access plate up.