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I am not Tmann45 but I will chime in (could not resist tmann). If you continually run and operate in the "all" position....you defeat the reasoning for two batteries in the first place. You are basically running with one big battery. The charging of both batteries from an outboards system while both are in continual use would be a trickle at best (and as stated earlier the weaker of the two batteries would steal charge from the good one) and you would be better off charging one without diverting the amps. To me the need for two batteries is like having a spare tire. One needs to be charged and in good shape for emergencies. Like Phil says, (and my opinion of the way you are using them) you may as well go for a single battery.

However, Dennis brought up a very modern and well thought out design for two batteries. I have the same system on my boat. My secondary (non starting) battery always gets the charge from the motor but the only function/draw I put on the battery is for the electronics (negligible). It is separated from the other battery. With the ACR relay.....you also protect electronics. Do study the Blue Sea system. Your wiring is already there and with some modification you would have a superior system with the charged (spare tire) available.

Garris

Dennis,

In addition to combining the charging the ACR Relay disengages the secondary battery when starting the motor. The relay is connected the the starting position of the key (not the "on" position). As you flick the start, some internal connection gets interrupted. Davits, anchor winches, wash down pumps, etc (the high amp surging starter motors).... should be on the starting battery if you are separating the electronics. All my electronics are isolated.

Editing