Battery question

[Facility Dude]

Have 70 HP 1981 Evinrude and have two batteries, one for outboard, the other for trolling motor. Question is, can I hook the two batteries together in parallel? Would it tax the motors electrical system trying to charge two batteries? I know the difference between parallel and series!

[boats.net]

Yes this will tax the charging system, will also kill your starting battery from use.