I'm not sure as to what to check next. If the battery leads from the switch to the engine were the problem I would have a amp draw when I test the #1 battery
I started over and rechecked my readings and I screwed up on the reading on battery #1. Sorry about that, It is the same as #2. I went also from both batteries to the positive lead to the engine and found the readings to be the same. The boat is a 1972 Mako and the battery cables are under the floor. I guess I can take a resistance reading on both cables to see if they match. If I get a higher reading then I would think that is my problem. Am I thinking correct on that ?
Don't bother with resistance readings. They are pretty much useless especially with what you are trying to find.
A 1/2A draw is not good but it is not why your battery drops over 8 hours. However, if it's been going on for awhile and it has caused your battery to get completely drained a few times, your battery is probably not good anymore.
Next step is to have your meter in the circuit and start pulling fuses until that draw goes away. That will identify which circuit is causing the draw.
Only have 2 circuits. One is the GPS and the other is a switch panel for live well, bilge pump and lights. These are connected to the battery with ring terminals.
They check good, Removed the positive terminal from battery and removed the positive lead on the motor, Cable is 15 ft long with nothing connected to it. I get an amp reading of 00.49 It must be the positive cable,
I once had a split in the insulation on my positive battery cable. The split sat in the salt water, and the boat had bolts thru the hull connecting the bilge water to the bay. Overnight the battery went dead, and the battery cable turned to green paste.
