Good advice.
Getting a good clamp meter and learn how to use it will help. A killowatt device from Amazon helps too. You need to know the power consumption of whatever devices you're going to use. And you can circuits for good ground, power, etc.
More than once I have had marina people tell me the pedestal is working fine until I plugged my meter in and had them read it. Then they're like "Oh wow, I'll call it in."
Lots of good books out there. I happen to like Nigel Calder's "Boat Owner's Mechanical and Electrical Manual". He has all the formulas in there. You can ramp up on this pretty quickly. For example if you have a coffee pot you want to check for power consumption, look at the UL sticker for the watts. Let's say it's 500 watts. At 120 volts, divide 500 watts by 120 volts, and voila, you now know you consume 4.16 amps for however long it takes to brew coffee. That gets you pretty close. No meter required.
However, I feel its always more accurate to check with an actual meter. If you do get one, look for one that can measure DC amperage. Many don't have that. I use a little Sperry. Lots of better meters out there, but I haven't found the need myself. It's small and fits in my tool bag. My father always said the best tool is the one you have with you when you need it.
-martin
