Recently bought an older 14 FG runabout in very good condition (needing help positively identifying the boat..thinking it's mid-60s) with a 1957 Evinrude 35 hp Big Twin which also seems to be in very good shape. This engine has no generator or alternator. Am I correct in assuming that there is no system to charge the battery other than an off-boat charger? Any advice on the best way to do this and keeping track of charge would be greatly appreciated. BTW, the boat has a push button starter, and running lights, no other electrical draws.