starting battery drains

[Musky Guide '41]

When I isolate all ground cables from negative battery post, and insert meter between a cable and ground post,every cable shows 12v. Cable A runs to 2012 9.8 kicker, cable B runs to 1998 75 hp. Merc, cable C runs to console fuse block. Each cable also shows ma drain.How could all be bad as indicated in another thread. Had no problems for 5 years and I thought it was 2006 battery so replaced. Sat for 3 weeks and found new battery dead @ launch again. Help....

 

[robert graham]

Maybe your new battery didn't have a really full charge, then sat for 3 weeks and drained down some more?.....for anything more than a couple of weeks of not running my boat I take my battery out and put it on a 2 amp charge overnight to keep the battery topped off.....

 

[Musky Guide '41]

Thanx for reply rg... boat had been out after new battery install a few times.... but fractured foot and did not get out on Charter for almost 4 weeks, that's when I got to ramp with totally dead battery, not even a horn... It was suggested that I just install a battery disconnect switch... I have one on my 24v. system up front for the trolling motor...

 

[Silvertip]

If this boat has a radio, the station memory draws a small amount of current. If you leave a locator on by accident, or if you have an automatic bilge pump that cycles itself that can draw down a battery. A bad rectifier/regulator on either or both motors can cause reverse current flow. A battery disconnect switch will prevent a dead battery but it doesn't fix the problem.

 

[UncleWillie]

When I isolate all ground cables from negative battery post, and insert meter between a cable and ground post,every cable shows 12v. Cable A runs to 2012 9.8 kicker, cable B runs to 1998 75 hp. Merc, cable C runs to console fuse block. Each cable also shows ma drain.How could all be bad as indicated in another thread. Had no problems for 5 years and I thought it was 2006 battery so replaced. Sat for 3 weeks and found new battery dead @ launch again. Help....

You would expect to see 12 volt on the open connections. Completely to be expected.
Voltage and No current is what an Isolated battery IS!
How many mA do you see on each cable?

A Starter battery is in the 100Ah range that is the same as 100,000mAh.
Even a 10mA drain will take 10,000 hours to deplete the battery completely. That is over a year.
You would still have over 90% remaining after a month.

So again, How many mA specifically, do you see on each cable?