bpharris, Trolling#2 battery is likely dead if it is reading 6volts. Take them all somewhere and get them tested. I think Autozone does this for free. That doesn't explain your cranking battery. Post a pic of your cranking battery with cables connected.

One thing, if your batteries are near fully charged and you are measuring them having 15 volts while charging, get a new charger that steps the voltage down as it gets near a full charge. Staying at 15 volts may damage the battery. Most new chargers will cut the voltage down to the low 13 volts when its near fully charged.

If you only have 6 volts on the battery you have a dead battery. If its been shorted and lost its charge it still may be good. If you have a manual charger with a high amp setting try giving it a couple 5 second shots at full amperage and see if it starts charging. Do it soon as a dead battery sulfates fast.

I can't figure out your dead starting battery though.

Maybe Lou can answer this but it almost sounds like you may have an intermittent problem. I think you may have a broken battery terminal that can possibly show good at times and then dead.

troller #2 is shot, replace and match to the other one for size and reserve capacity.

get start battery load tested, if it tests good then you need to start on the engine side to see if you have a power drain. a hung solenoid, bad starter, no output on charge circuit etc. start with the easy stuff and let a shop do the hard.

Battery test on the cranking batt came back GOOD! Trolling batt #2 is shot. Replacement installed.

I gotta be honest, I don't have any idea how to check the solenoid, starter or any of that other "easy" stuff. But, the batt is definitely not my problem. Any tips on how to run through some basic checks would be appreciated.

When you have problems cranking, does it try to turn over or just no click or anything?

You're an EE and you don't know how to check electrical stuff???

I think you read it wrong..he's saying Lou is the EE....

Both times it died on me, the engine would turn over but not enough to start it. After trying a couple times, it would go completely dead and not turn over at all.

I didn't really think about this until today, but both times when this happened and i switched the cables over to one of the trolling motor batteries, I never had the problem again for the rest of the day. But, again, I had the cranking batt checked today and it was good. If it was a problem with the engine, I would think that the same thing would happen when it was attached to a trolling motor batt.

No, I am not an EE! But, I believe Lou is.

If you want to continue to DIY I would take one of your TM batteries and leave it as a cranking battery at least to test. Just don't crank your engine too much on the TM battery or run your TM too hard on the crank battery.

I'm no EE just an ET. lol

when you switch power leads are the acc leads staying on the start battery? if so then start checking acc circuits for resistance, shorts, one may be shorted out only when the key is on and just pulling a lot of amps quick. this should pop a fuse/breaker but sometimes won't.

other than that not sure, bad starter would have pulled the tm battery down too.

Either bad battery connections or loose connection somewhere. You need to check battery cables at motor end. Also, make sure that something isn't running continuously like a pump. Connections at battery need to be motor first then accessories. Lock nuts on terminals, not wing nuts. Do you have a battery cut off switch?

I have had battedries that they tell me were good with the little testers some people use that were actually bad. They were just getting the surface charge test. They need to do an actual load test to get an accurate test on it.

Kris,
I have checked the connection at the motor. It is solid.

I didn't know the connection order on the battery mattered. But the accessories and on-board charger cables are on there first and the engine cables are last. I'll switch them around. I use a regular nut on the battery post, not a wing nut. No battery cut-off switch.

I'm really starting to think its one of the accessories that's causing the problem and not an engine issue. The battery was tested at O'Reilly's in their battery testing machine - not just on a volt meter.

I had the same problem about a year ago bought a new starting battery and after about 6 hrs on the water it was dead took it back got another one and same thing happened. Both those batteries 675 amp bought a 1000 amp and solved the problem. Just had too much stuff running off the battery 2 graphs w/structure scan,Talon pole and live well pumps.

What motor do you have?