1981 galay 1978 L6 165 merc outdrive, when shifting into reverse sometimes it sounds like its in nuetral . some history, the screw that holds the throtle /shifter in place became very loose thus causing the throtle/shifter to slip into a different position . put it back almost in the same position . been working ok but had slop between reverse and forward . after running wot a few minutes i slow down to idle speed which is a little high ,800 rpms. put it in neutral goes in forward with a little thud back to neutral and when trying to go into reverse it sounds like automatic transmision slipping kinda, so back to neutral into forward and back through neutral into reverse with a little thud .a new shift cable or ajustment is in order ? or something more serious ?would the throttle/shifter problem have caused most of this ? all comments welcome. thanks