A few weeks ago I noticed my cranking battery was dead on my 2015 Nitro z7 fish and ski boat. Replaced the battery and it died after a couple of days. Replaced it again and again it died basically overnight. I charged it back up to 100% and checked the drainage and it was running 4 amps, which I wouldn't think is enough to drain it like it is doing. Any thoughts on what may be my problem or a better way to trouble shoot. BTW my Main Power switch has been off on all of these occasions. Any help would be greatly appreciated..Thanks, John