Battery Tender for winter help

So I keep my boat outside during the winter but remove the batteries. This year one of the batteries was dead when I re installed it. So im looking into some battery tenders to keep then charged during the winter. I have the blue top optimas and was wondering if anyone has experience with a tender. They may be called trickle chargers. Ive found a ton of different info and am having trouble making a decision and finding the product i need.

Any help woudl be great. Ive been told i need one for 1.25Amp, not the 750Amp ones.



Thanks
Rob