deep if all it does is run graphs, combo if you want a backup starting battery also.

You have now provided most of (but not all of) the "good stuff" we needed to know. As you crank the engine, the starter is putting a big load on the battery. The voltage of a marginal battery will drop significantly when that happens. It sounds like something is very wrong if it shuts down when you activate the trim while running the outboard. (The electric motor for the hydraulics also puts a load on the battery, but if the engine is running above idle, the engine should be providing power.)

There are couple of simple things you need to do before you start fixing a problem that doesn't exist. If you get another battery, you still aren't fixing what is wrong in the first place, and you're going to have more trouble later, and it may not be fun. "Solving" this by adding a battery is not solving the issue - it's just working around it until more trouble develops.

Get someone with a voltmeter to help you a bit. If you have water muffs, you can do this at home. Take a voltage reading of the cranking battery. Then crank the engine and run it at about 2000 RPM while you take another voltage reading. You should see 13.8 - 15V depending on the motor you have (you haven't said yet). If you are only seeing 12V or less, your outboard is not charging the battery.

Next, tell us what main (cranking) battery you have, and what outboard you have. How old is this battery. If it has removable caps, have you ever checked the electrolyte level in it? Do you know what a "properly filled" battery level is? (Hint: it's not filled to the brim.) Remove the battery, take to auto-parts store and ask them to load check it. My guess is it will not pass a load test because it is no longer serviceable. This battery will likely fail to start your outboard one day soon. When we know what engine and battery you have, we can advise what to replace it with.

Adding yet another battery to a boat that didn't previously have a problem is not the way to fix this.

If you add another battery, you cannot simply put it in parallel with the starting battery. If you do that, and the starting battery is bad now, or fails in the future, it will discharge the additional battery and then that extra won't do you any good either. An added battery needs to be charged, so you'd need another battery charger as you'd need to charge this one after every outing.

Speaking of chargers and batteries, I assume you have a trolling motor also (12, 24, or 36V) and that you charge those batteries when you return from fishing (that day, not later)?
You should also have a charging bank connected to your starting battery and recharge it after every trip. This is because most people don't run the outboard long enough to replace the energy used by other devices like pumps and sonar, etc. Do you have a charging bank connected to the (likely failing) starting battery? I'm betting you can guess the correct answer for this, LOL.

On my previous boat, I used a wheelchair battery. But I only ran one Helix off it. Easy to pick up and recharge in the garage.

Flip, you are making my head hurt!!!

But definitely thanks for the input. I load tested the battery with my load tester and it was holding above 13V (held for about 5-7 seconds)
On a side note, the volt meter guage on my dash (Old boat 1996 so I don't necessarily trust it) drops down below 11V when I crank and when
I trim..........So, your idea to load test while running is a good one.

I hear you that I am not solving my problem and you are right. My challenge is that I live in Dallas and my boat is in storage at Fork.
So very difficult to muff it and test it with the motor running but I may be bringing it back to Dallas in the next month or so and can do
it then.

I have an interstate (27 series I think) starter battery, approximately 1.5 years old. I have a 1996 Suzuki 150V motor on the back.
I have an onboard 3 bank charger (whatever came with the boat, so OLD) that charges my two trolling batts plus my starter batt.
I have considered the possibility that my onboard charger is not doing its job, but the deep cycle batteries seem to be fine and
when I load test the starter it seems fine? Additionally, I do not get out very often. If I am lucky, I get out for a 1-3 days a month and
run it. I have always been told the worst thing you can do to a battery is let it sit. With that being said, I should check the water in the
batteries. (but I haven't)

If I load test the battery while the outboard is running and it drops down below 11V, meaning the outboard is not charging the battery
when running.............what does that mean? Is that an outboard problem or a battery problem.

Also, buried in all this is the wiring, which is obviously old and appears to be all wired through a circuit board of some sort.....could this all
be just old/bad wiring?

Yes, my head definitely hurts..........

Thanks again for your time Flip!

Tommy

I want to be clear that I am not asking you to load test the battery with the engine running. I simply want you to use a handheld digital voltmeter to take a reading of the battery sitting at rest, then crank the motor and take another reading with the engine RPM up a bit, not just at idle. I'll pick 1500 RPM for fun. You should see the voltage reading on the battery go up with the engine running and reved up. How much it should go up I'm not sure of for that Suzuki, but I bet 14V or better. If the voltage stays the same as when not running, that tells me that your outboard's charging system is out of service. This is a load that therefore drains the battery as the day wears on - to the point where the voltage drops lower than expected.

Some voltage drop will happen when you apply a big load to any battery. The drop you observed while cranking or trimming does not in itself say anything is broken (yet). Since I only asked for voltage readings, you can do that in the water at the lake, and there's no need to muff it or bring the boat home. I was just assuming you had easy access to the boat on the trailer at home, and that was wrong. I want a true reading with a handheld meter, not the "rough number" reading from a cheap dash instrument. What we are looking for is a rise in that reading once the outboard is running above 1500 RPM. You could also take readings of each battery voltage while your charger is still running. That's a good way to confirm that the charger has not malfunctioned at any time you question its operation.

While it is possible there's "room for improvement" on how your graph is wired for power, the fact is (apparently) that this worked fine in the past, so something somewhere has changed. It's either in the wiring, or the power source. The power source is the easier to troubleshoot. What you do after this depends on the test results from above. Example: if the Suzuki isn't charging the battery as you run it during the day, the battery is now getting weaker and weaker as the day wears on, so an issue results. If all else fails, another option is to run two new wires from the battery to the console for electronics power. What gauge wire I recommend depends on what will be powered. There will be fuses involved also; skipping those is dangerous.

Ok, next steps then are to get a voltage reading while the boat is running. I will do that next time I am there (maybe a couple of weeks)
and report back what I find out. (will also get voltage reading while plugged into charger)

Thanks again