I just took the big leap and bought my first boat tonight! Its a 1965 Hydroswift 16.5' long. It has a Mercury 650 engine that came with it. The owner said that the lower unit was drained the last time it was used (3 yrs ago). So how do I go about servicing it? What kind of oil? Anything I should know about this motor? I'm not well versed in boat things (yet) so I will pick your brains if thats alright.