Re: Battery life short? What to check?
Jim, there could be a lot of stuff wrong but if the yard didn't say anything about the mixed battery types being a serious problem? They're greasemonkeys, use 'em for brute force labor but try to ignore anything technical they may say.
Mainly what Maine said. And if you look at other message threads, buy one of the popular and inexpensive "twelve volt" books for boats, or check around the web, you'll get plenty of answers. If a system is not set up from the basics, you can throw a lot of money at batteries, year after year. After year.
Take the time to learn the groundrules, and you'll be well paid for your time with the savings.