I just replaced the upper gear case bearings and unfronze shifter cable that was stuck and replaced water pump in my 1979 OMC 800 outdrive w/350 Chevy, 260 hp. It will shift into reverse ok but shifting into forword it grinds. Acts like it is not sychanizing. This Pursuit has been setting for about 2 years. The engine runs great. Can you give me some ideas on how to fix the grinding. 