I own a 2003 16' Fisher bass boat with 25HP Two Stroke Merc. I have room for only two batteries, one cranking and one deep cycle.

Most of the fishing I due is on lakes and ponds, which require electric motor use only.

Question:

Can both batteries be hooked together and still operate the outboard motor and trolling motor? How? The benefit would be longer run time for my trolling motor with occasional use of outboard.     :-/

 

A couple of concerns involved but if everything is right, no problem.

1. If your cranking battery is just a cranking battery and not a dual purpose, it's not designed to be deep discharged or discharge a large number of times like the deep cycle battery. Using it as a trolling battery will greatly shorten the life.

2. If you run too long and run them down, you're starter is not going to crank the motor when you get ready to use the motor. If an isolater is available that will only let the cranking battery disharge to a certain level and the take it out off line, then I would seriously consider adding one.

3. Many outboard charging system are only designed to top off a battery after is has been used to crank the boat. Prolonged charging will overheat the rectifier/regulator or stator and cause them to burn out. If you run the TM for a long period and then run the motor for a long period, this could cause you an expensive problem

If both batteries are deep cycle or dual purpose, and your only using the TM you shouldn't have a problem

You would connect the two in parallel, positive to positive and negative to negative.