I have a 2-bank onboard charger for my two trolling motor batteries, but I have to hook up an external charger for my cranking battery.  I really like the convenience factor of plugging in my charger for the trolling motor batteries, and would like to get a charger for the cranking battery that will recharge the battery and also keep it charged up (plug and forget).  What type of charger would be recommended for this purpose?

Thanks.

For that, I would just get a something like a 1 amp maintainer.  

I just run into the same problem. I upgraded from a 12v to a 24v trolling motor. I already have a Minn Kota MK210 in the boat that has been great with no problems,so I ordered a MK106 from Cabelas for 69.99 plus you get a 15.00 rebate and three year warranty. That was my solution.

Regards;Wayne

Looks like they have it on sale at Cabela's and other places on the web for $54.95.  It seems that price is before rebate, so I will definitely be considering a mk106.  Thanks for the info.

Jeff