I just baught my first boat with a 1987 Johnson seahorses 50hp. Ran great first day I took it out next day I launched and didn't make it 100yards and it started jumping in and out of gear then wouldn't go into forward gear but will reverse fine. I took it home and manually spun prop with shift lever all the way forward little resistance counterclock wise and pumped motor clock wise so I check reverse and it pumped motor both way so I adjusted shift cable and it was same resistance both directions in forward same in reverse so I hooked it up to water and it seemed to spin the same put it in the water and it will push the boat forward at idle but slips out when I give it more throttle and reverse was still good as before. Back at the shop I disconnected shift cable under the cowl and I can manually shift in reverse but will not go into forward gear. Drained LU oil and it looks clean no metal. Is there any shift adjustments to look for? If so where? Thanks for any and all help!