Hello all,<br /><br />I have read the numerous threads about 2-battery systems and isolators, but have not found anyone addressing my specific questions.<br /><br />My boat is a 15' tri-hull with a 70hp 1978 Mercury O/B. I use the boat to run around local lakes and bays, and I would like to be able to go just offshore (1-2 miles out). It is likely that the motor will never be at WOT for more than an hour at a time.<br /><br />I currently have a single "Cranking" battery. All other electricals (lights, VHF, sonar, etc.) are attached to this battery.<br /><br />I want to add a second, "Deep Cycle" battery to operate a 12v trolling motor.<br /><br />The guys at Mercury tell me that the O/B charging system puts out "40 amps no load, 100 amps cranking."<br /><br />Question 1: is this enough juice to charge both batteries through an isolator, especially considering my usage pattern?<br /><br />Question 2: what capacity isolator would I need? Is 42 amp enough, or will this burn out during cranking?<br /><br />I know I should put down the bucks for a 2-bank onboard charger; but I already have a portable 1-bank 2 amp/10 amp charger I ought to be able to use.<br /><br />Question 3: can I charge the batteries through the isolator using the single-bank portable charger? If so, do I have to disconnect anything else? Can I connect the negative posts of the two batteries together to ease hookup of the charger?<br /><br />Question 4: should I connect the electricals (lights, VHF, etc.) to the cranking battery or the deep cycle?<br /><br />Thanks.