Two battery boat question

[Yatabata]

This may seem like a dumb question but something I was not aware of. When I went to hook eveything up this year I was getting power from the battery for the console lights but the engine was not turning. I went through many things to figure it out and found when hooking up both ground cables to the battery the engine now cranks? I thought the other grd cable was for the 2nd battery if used? Without digging into this puzzle thought to ask you guys. Thanks

[Amx]

Ground cable for the equipment on the boat, and a separate ground cable for the motor.

[Bodofish]

It all depends on how they're wired, sounds like one batt runs the house and one the engine. You probably have a battery selector switch somewhere. It will have battery's A and B on, off and both. If you have a lot of electronics and run off your trolling bank, you need to insure you have a battery for starting at the end of the day, after fish finders, stereos and what ever. Two batteries is a good thing. Saves a lot of paddling.

[Onmygame]

First off, I'm guessing you didn't do the wiring -

Secondly, it is typical for a 2 battery system to have different tasks for each battery; lights, aux, electronics, sub pump on one as an example,..and electric start / trolling motor, etc on other.

While your description is either a bit vague, or my inability to absorb prevails - am guessing at least one of the batteries had a poor ground, so no output.

That it is now attached to a good one (ground), you should be up and running.

It is best though, to find the issue with the problematic ground, as things such as corrosion tend to expand, and are best headed off at the pass.

Someone else will likely be along with more, the best of luck.

onmygame

[G-Man]

Whoever set up your boat's wiring looks to have avoided using a single point ground line which is a good thing. Avoid using your boat's hull, if it is aluminum, as your ground plane and remember that electricity is a closed loop system. Each battery needs to be connected to ground, in a 12V system, and this sould be the only common point the battteries share, if you want to keep them separated.

[Amx]

Does that boat have 2 batteries?

Does it have an electric motor in addition to the gas motor?

Or does it only have an electric motor?

Or only a gas motor?

You say: 'engine not turning'. Therefore it sounds like it has a gas motor that wasn't turning over to start it. But does it have an electric motor? And a separate battery for the electric motor, if it has an electric motor.

[Hunter757]

Sounds like you fixed the problem. I don't think you are running 2 battery's you are running one and thought the extra ground wire was for a second battery. After hooking the extra ground up your main motor worked. There are often two or three grounds to the battery depending on how someone wired your system or add on's at a later date. The wire you did not hook up was most likely the main engine ground wire.

Sounds like you just forgot how many wires you took off at the beginning of winter. Now you know!! Sometime taking a picture with a cell phone before you take things apart come in very handy when reinstalling things.
Glad you got it corrected good luck and be safe.

[Yatabata]

Yes that is exactly what happened. What is interesting is the times before when I ran the boat I only had one ground cable connected. So now I wonder what wasn't working without the other grd cable hooked up? Guess I will find out and will put both batteries in this time. Thanks