Take to auto parts store they test for free usuallyhere is the one I have, but mine will charge two batts. at one time so it's actually putting out 5 amps.Guest ChargePro Battery Charger
When I'm at the dock it's running and when I'm all charged up it goes into float mode. If yours is working then I'm sure your fine . To check if your fine , a volt meter, $10. and a hydrometer $15. from a auto parts store is what you need .
Die hard charger not cheap http://m.sears.com/index-g.html#/diehard-battery-charger-maintainer/p-02871219000PAre you in a slip and do you leave it on for extended periods? If so, check the voltage. Some inexpensive chargers will overcharge and ruin the battery
If the charger shorted and caused a fire I would also assume that the onboard electrical panel was not doing its job at the first of a short the breaker should have popped and stopped the short from getting hot enough to start a fireMy .02 is NO, don't use one of these "non-marine" chargers for your boat. If a trailer boat, OK. If in the water boat... Even as simple as the thing is, it may or may not have the protections that are built into a perminant on-board battery charger system. There are documented boat fires with garage battery chargers as the probable culprit.