Gears or shifter cable

When puting motor into reverse gear a grinding sound is heard, also will occasionally hang up and not go in reverse, This is rare and will probably do it 1 out of 10 times. Thinking cable but gears are in the back of my mind, however do not believe it is gears due to the fact that at times it works fine. Any advice it is a 2005 Yamaha 90hp two stroke

[jb123]

unhook cable and manually engage