Re: Battery Drain?
As mentioned, batteries can self-discharge, but it doesn't sound like that's your issue. Especially considering the battery is very new.
This is not a normal situation, and it worries me just how much current you'd need to draw to kill a battery in 30 minutes.
I look at Interstates reserve capacity of their marine batteries and see a BIG window, but assuming you're running the smallest battery it's still 100 minutes @ 25A. This means you're drawing far in excess of 25A to kill a fully charged battery in 30 minutes. Yes there's 10 starts there but that's a combined pull of ~150A for a total of what, 30 seconds (3 seconds crank per start)? That'd hardly touch the reserve.
The lack of responses is likely due to the lack of information. Other than knowing it's a 72 Evenrude we know nothing about your boat. What kind of vessel are we talking about? What kind of lighting are you using? Have you used a volt meter to see how much current you're losing? Have you removed the fuses from the boat and see if the draw is eliminated?
Here's how you can do draw test; Disconnect the positive lead and vice-grip a test light tip to the battery post. Then put the alligator clip from your test lead to the positive cable. You're putting my test light "in-line" with the power flow of the boat. If the light shines, there's a draw. A very dim light is acceptable in a car (clocks and keep-alive radios). Full brightness indicates a draw of at least 3 amps - unacceptable. Next, remove the fuses one-at-a-time and watch the bulb. If it goes out, or significantly dims, that's the faulty circuit. Then you're physically tracing the wire and figure out what's shorting.
