I'm working on a new project outboard. a 1970ish Johnson 6HP I picked up a 1977 6hp for donor parts (mid, lower, and transom clamps, hood upper and lower, carb...) However, I don't know to take them off. I tried to take the bolt off the back (which the 70ish doesn't have), remove the base, and screw them out, but when they get to the base they stop. Ideas?