I am in the process of dealing on a boat package. Great deal.

Problem. It comes rigged with a 55 lb. 12 volt bow mount system. The boat is 1200 pounds dry plus the 115 OPTI. We fish in bigger waters, so I want to upgrade the system to a 70 to 80 lb. with 24 volts. I see from the product specs that the boat only has storage for 2 batteries. By my calculation I need 3 (1 for starting and all else & 2 exclusively for the trolling motor). Is a conversion possible with storage for only 2 batteries ? Please let me know if you can help out. Local dealerships do not run into this much. Thanks.

Any boat with a 115 should have room for two t-batteries.

My old ('84 model) boat doesn't really have a compartment for any batteries. Obviously, the starting battery is under the splash well at the rear of the boat.
My two deep cycle batteries for the trolling motor can be set under the driver's console, but that made the boat too bow heavy. So I ran a couple lengths of heavy gauge wire from the rear of the boat to under the driver's console, and tried having all three batteries in the stern. Too stern heavy.
I currently have one deep cycle in front of my feet and two batteries under the splash well. The boat balances quite well this way.

The point is that you can screw down a battery tray almost anywhere in your boat that's not underfoot and with some 4 or 6 gauge wire run the power wherever you want.

Thanks.