Guest battery charger 3 bank only have 2 batteries

[GoPackGo78]

I was given a Guest 2613 charger which is a 3 battery charger 1 starter and 2 accessories charger. My boat has 2 batteries and the manual on line does not show wiring for 2 banks. Can I plug for the starter battery and one to the accessory leaving the 3rd set of cables free? Ideas?

 

[oldjeep]

Says right in the directions that you can wire outputs 2&3 together to create a 10 amp output 2613A Connection Warnings: For the 2613A, only output 2 and output 3 may be
connected in parallel for a 12 V 10 amp output. The engine start output (Output 1) may not be connected in parallel with output 2 & 3.