Yamaha 70 Hp Outboard Shifting Problems

need help trouble shooting stift shifting from N to F and R, now will go in F and N, but now we have lost reverse, if it goes forward, is it the cable? how do we check? what else could it be? thanks in advance for any info.

[boats.net]

Disconnect shift cable and shift motor by hand to see if shifts into reverse, if not could be upper shift shaft or problem in gearcase.

Thanks

will do today, thanks for the reply.