1970 thru 1990 TRS
TR & TRS both have a transmission inside the boat. There is no shifting done inside the outdrive itself. The upper drive shaft housing is the same on both units. They both have a removable rear cover "A" with 4 bolts attaching it.
A TRS has a much smaller lower gear housing and uses a propeller "B" between 14 to 16 inches in diameter. The wrench to remove this propeller is a "C" 1 1/16.