Hi, i have a 1973 50hp evinrude. The model number is 50373R. I have the lower unit off right now because of an impeller change and I cannot get the lower unit to shift into reverse. This motor is new to me and I never attempted to shift it into gear when everything was together. When I push down on the shift rod and shift it into neutral and forward it takes alot of pressure. I also have noticed before when everything was still together the prop shaft moved smoothly in forward gear. After I pulled it into neutral, when I go back into Forward the prop shaft is now very stiff and is not turning without alot of help. I did empty the gear oil and their was metal shavings but not alot and nothing big. I'm not sure what is wrong. Any help is greatly appreciated.