If you are using this motor for charters, I would make sure it is very dependable. First, I would get some good di-electric grease. Hardware stores and auto stores have it. I'd remove every wire and brush on some of the greas and get everything good and tight. I'd check cable ends to make sure they are tight. This grease will prevent coroding without hindering electrical conductivity. In other words it is a conducter. You can put this grease on battery terminals too. I would then try if several times to make sure there is no repeat of the problem. If you have any hint of a problem, I would take it somewhere ad have a load test done. This will let you know if current is hindered or lost through any component in the starting cycle.
