Re: 1986 merc 90hp
Hi,
Well it seems that your clutch dog (#56) and maybe your Forward gear (#54)
may be bad. If you adjusted your cable to allow full engaugement and it now grinds without going anywhere I am afraid you will need parts.
http://www.crowleymarine.com/mercury_parts/278/23.cfm
One other thing you may want to check is #70 This spanner nut should be locked in place by the lock ring #69. If someone did not bend the tabs to make it lock it could have backed out a little and created the problem you have. I would drain out a couple of ounces of lowerunit oil and see how much metal is in it. Chunks are bad as are a lot of fillings or chips. It is rather rare for a Merc clutck dog go out. I have seen them split or crack in half but not rounded off like the older OMC dogs would get.
If anyone else has an idea feel free to jump in with a idea.