Hi mitch-houser,I think I'm going to make a fool of myself,again,but here goes. I went back over all your posts about this motor and the number you give is for a mid '70's. So here's what I read somewhere,maybe even on this forum,
http://www.marineengine.com/boat-forum/showthread.php?396386-1975-50hp-thunderbolt ,that these motors need to be running to shift into reverse. Not sure if that is true or not,and I'm damm sure someone will be on top of me very shortly to correct me.It is not logical,and I think along the same lines,if you shift the lwr unit into reverse while it's off the motor then it should turn the prop shaft CCW while the drive shaft is turning CW.It does on the spare I have in my garage,but that is of a different engine,a 650. This is the number you posted,1968 Mercury 50hp s/n 4043524 ,and it is still the same motor? '67 -'75 number range compliments of TMD
500 (50,0) 2097445 - 2305100 1967 4 cyl
500 (50,0) 2305101 - 2514918 1968 4 cyl
500 (50,0) 2514919 - 2736806 1969 4 cyl
500 (50,0) 2736807 - 3008818 1970 4 cyl
500 (50,0) 3008819 - 3235062 1971 4 cyl
500 (50,0) 3235063 - 3478002 1972 4 cyl
500 (50,0) 9001581 - 9006163 1972 4 cyl
500 (50,0) 3478003 - 3816307 1973 4 cyl
500 (50,0) 9006164 - 9047653 1973 4 cyl
500 (50,0) 3816308 - 4140999 1974 4 cyl
500 (50,0) 9047654 - 9082513 1974 4 cyl
500 (50,0) 4141000 - 4357639 1975 4 cyl
So can you get someone to turn the prop CCW while you turn the the shifter CCW from the N position? And good job no one will be able to see my face when I get laughed out of it.