'1983 Mercruiser 260 - loud grinding/knocking when going into gear

I have a 1983 Mercruiser 260 that has had this problem since i got it several years ago - there is a relatively loud knocking/grinding sound when engaging/going into gear. I used to be able to just go into gear faster/stronger and it would clunk into gear, but now the problem has gotten worse and the grinding persists into higher RPM's. Where should i start? Cables, clutch? Any help would be appreciated as i don't have much experience working on Mercruiser engines. FYI, i have been reviewing other similar threads but they seem like slightly different problems and i would like to get to the heart of the problem, if possible. Thanks again.