just a regular ol 12v charger here.  once in a while I'll hook it up and turn the lights on in the boat and drain it some and then charge it back up.  from my experience batteries dont like to sit around charged and lead acids do NOT like to be below 12v ever unless its a deep cycle.  i just leave it in the boat without the cables connected.  so far so good. 

with 2 battery types like that, id try charging them independently.

Same as mentioned above on the walmart... have one on my 56 and another in boat with easy disconnect. I have it wired into my perko (2 batts)with the disconnect near the floor. Makes it easy to charge both or one at a time.

i have a battery tender for every one of my toys.

I bought a Schumacher a few years back.  I have it to a buddy.  I prefer my dads old Montgomery Wards brand charger old as hell but trusty.  I have a Battery Tender for the Harley works great but I wouldn't use for dead battery just used to keep a charge