Hi, I've got a 1985 Forester 16' runabout with a 3.0L Mercruiser I/O 140HP that is/was in pretty good shape for being 25 years old. It's never given me much issues, and NEVER ran hot. Well, I was attempting to boat up to see the fireworks on the 4th, and while cruising around 3500 RPMS, the...