Garmin Gpsmap 431S Plotter And Fish Finder

[merckxrider]

I have a 14' Alumacraft w/ a 1972 Evinrude 18hp Fast Twin. I don't have an alternator. I run my 40# Motorguide Bulldog and homemade livewell on a decent sized 12 volt deep cycle Wal-Mart battery. A full day on the flats still gets me home with 80% battery left. Could I also run my Garmin on the same battery, or should I get another battery? If I get another battery, what size would be okay? Could I get away with a yard tractor size and get a full day's work out of it? I've done some customizing on the boat and have planned under deck storage potential, but I don't want to bulk up more than I need.

[Long Mike]

If I understand your question correctly, you are saying that you do not have a cranking battery for your Evinrude, but have a battery for your trolling motor.  If you have the TM battery only, and have 80% reserve power at the end of the day, you will be OK with tying in the Garmin with the existing battery, although some people have experienced noise problems between the TM and the depth finder.  On the other hand, if your Evindude has a cranking battery, by all means, hook up your Garmin to it.

[merckxrider]

Thanks Mike. The only battery I have is for the trolling motor. The outboard is a pull start. I think I'll get another smaller battery. I didn't think about the possibility of frequency chatter from the TM. I'll test it out first. Good info.