Last week I had some hesitation while cranking the engine after a long
run and some heat soak and wondered if it was the batteries or the
starter crapping out. I was amazed to realize that these batteries were
over 10 years old and this was the first sign of distress. Time flies
when you're having fun and not paying attention.

They were a pair of Group 34 Optima Blue Top AGM cells that I usually
run in parallel. AGM are needed due to a ~90 degree from upright
mounting orientation.

I replaced them with a pair of the Yellow Tops because they were in
stock at NAPA and I was in a hurry to get back on the water. The price
has gone up quite a bit but I won't complain after ten years of flawless
service averaging two outings a week, more than ten months a year, and
many start-cycles per outing.

There was no more hesitation from it last weekend so I think that did
it. A satisfied customer...

http://www.optimabatteries.com/us/en/products/