I used a 30lb thrust motor for years, not a quick as 55lb thrust obviously, but got you there and not that much slower. Just replaced with a 45lb Minn Kota Traxxis, got to say impressed as it seems to make the battery last longer, despite having more power - have a look at their blurb on the web.
I use a 110 amp leisure battery and have no issue with it. Charger is important and after spending money on various "Halfords type" chargers, some costing over £70, I was pointed in the direction of CTEK chargers, I've been using one for 4 or 5 years now with no problem, not cheap but they are definitely the best I've used and charge the leisure batteries with no problem.
Electric motors are great for stalking trout and I've used mine on slow speed to keep the boat drifting along a bank, wouldn't be without one.