1st with the exception of the specialty batterys, optima, and a few others, there are only like 3 manufactures of batterys in the u.s. all the store brand batterys ane made by one of these manufactures.

2nd as for the levels of batterys sold by the stores, use your head. there are different quality of batterys. most of the box stores have like 3 levels. say 39.95,49.95 and 69.95. even the most expensive one wont be as good as a battery store battery. the box stores dont get the good stuff. if you go to a barrety store they will usally only have one battery for sale. this id uaslly the top end battery by one of the true battery manufactures.

3rd im needing to replace my battery, also. it was a low end wal-mart battery. the smallest group car battery they offered. it has lasted 5 years with the worst treatment you could imagine. ( this is my worst trait, batterys. for some reason i can never take care of them. ive tried to make it a concious task, but still cant seem to treat them like they should be) that being said 5 years doesnt seem to bad.

4th my bro-in-law has a skag walk behind. its a smaller one with a 13 kohler. its a pull start w/o any battery at all. it has an electric clutch. now i dont know the difference between his clutch and a mm clutch but ide bet they are very simmular. at an idle the clutch will kick in. unless the motor has a hell of a charging system or the clutch is totaly different, it works. i cant see the 13 kolher making 20 amps at an idle.

Just replaced one of my trolling motor batteries (Walmart brand). The original purchase receipt in the plastice sleeve glued on the battery was dated 2004. I do take care of the batteries though.

I've have always used AC Delco Voyagers with great results. They are maintenance free, usually last at least 5-6 years and I only replace them as a precautionary measure. I haven't actually killed one yet. I use two group 27's in my boat.

I can't imagine that I'd get 12 years out of an Optima, so there's no way for me to justify the price with them being twice as much as the Voyagers.