Battery charging and regulator

[jjhadley]

I have a 250 four stroke susuki that I am starting my third season with. External power goes to a gps, vhf radio, sonar, and windshield fan. Last fall after running low rpms for extended periods, my gps would warn me that I have a low voltage problem, more so when I have to use my trim and tilt. When I install a new fully charged battery I don't have any warnings, but after hours of use the battery charge will go low. The motor runs fine and has all its power so the problem to me is the regulator. I see in the service manual that a susuki hand tester is the only one that should be used, Why?
Shouldn't all reasonalble electrical testers provide accurate enough readings? And if the problem can't be tested by generic hand tester, are there two volatage regulators on the motor? How do I know which regulator charges the battery or do both of them? Thanks for any suggestions.

[mitch]

how many amps are all the gizmos drawing maybe that you are using more than you are making at trolling speed