Hey hey, just got into the bass world bought a 1980 ranger 1600 v3 that has been in a garage since 1989. Got everything going but the trolling motor, it's a 24v system so that's new to me.  Do I need 3 batteries for my boat? I have a control unit at the bow that has a 12v/24v/and a 12v charge switch. 

 

So my question really is just if I need 3 batteries or if I can work the system off 2 for?

The trawling motor needs two deep cycle dedicated batteries.  Spend some time learning about the difference between deep cycle and starting batteries to save you a bunch of heart ache.  Getting the biggest batteries that will fit will give you more power and make them last longer.  31 group is what I would recommend, especially if you also plan to run your sonar off of them.  Lead acid batteries have the highest power density but requires maintenance.  A lot of guys are going to agm because they don't want to deal with measuring water levels.  Your cranking battery can be tiny if all your running is the starter, and small running lights.

Congrats on getting a boat.  Just remember that a boat is a hole in the water that you pour money into.

 

You don't say the size of engine.  Find out what CCAs (cold cranking amps) the engine requires and get something with more.  For trolling motor batteries the thing to look for is RC (reserve capacity).  I would not go below 180 and get larger if I could find them.  Brand is not real important as there are only a few battery manufacturers who make batteries under lots of labels.

 

If you want to try to stay away from electrical interference, hook everything except the trolling motor to the cranking battery.