i have a 74' mercruiser 140hp 3.0 ...... my problem is i fired up my boat for the first time with muffs on , and i can not shirt my control box ( shifter ) forward .... i can shift it in reverse and neutral fine , just cant shift forward it seems like somethings jamed ? any ideals shifter cable ? if so which 1 and how hard is it to replace? thanks for any help