The Magnetek 6300 series converter WILL overcharge your battery.
The Magnetek 7300 or 7400 series may or may not overcharge your battery, depending on whether or not it has the timer option ("T" suffix in the model number). Problem is, if it has the timer option, it may never fully charge a flat battery. The timer cuts off the charging too soon.
My new TM has a completely new converter from American Enterprises (ironically, I think, a Chinese outfit). It should be better than the Magneteks - completely filtered power, more charge capacity, and a couple other goodies. However, there seems to be NO information available about it, so I am not yet ready to recommend it wholeheartedly. When I called American Enterprises to get some info, the rep told me that it charges your battery to only 98%, so as to avoid overcharging. This is not an ideal situation either, but is OK I guess. He also said that they do not make any printed information available. I HATE that! At least Magnetek made the info available.
I don't know when TM phased in the different charger models. My '02 had a Magnetek 6300 series, my '06 has the American Enterprises unit.
Bob Rederick replaced his 6300 converter with a Progressive Dynamics Intellipower PD6000 (?) - use the Search tool at the top of the page to find his posts. On paper, at least, this is the best converter I have seen.
I continue to recommend, as I have for years, that for long-term storage, you should get a true 3-stage (or 4-stage) charger from one of the mfrs that specializes in chargers for electric trolling motors. One such mfr is Guest Industries, and there are others. I have used a Guest Model 2610 10-amp charger, leaving it connected for months at a time, without problems.
http://www.marinco2.com/showProduct.asp?p=2610
If you don't have a true 3-stage charger, I recommend fully charging the battery, and then completely disconnecting it. With no load, it will stay fully charged for 6 months in cold weather, and probably half that in warm weather.
Bill