merc i/o 165

[doctordelerious]

I have an 1987 thompson w/ a merc 165 fwc, it has seen about 12 hours running time over the last 5-6 years, she tends to overheat, and the last owner was a mechanic, great shape otherwise and she turns over hard sometimes, almost like there is a weak spot in the starter and she missfired the other day when I ran her 4 the first time this year as she was turning it briefly spun backwards, timing ?? what routine maintainance should be done should I replace both impellers and the t-stat ? im green to the points thing should i clean them ? and the timing can it be checked with the light ?? I have the manual but im sure someone can give me a non textbook answer
Thanks, Aaron