The issue I'm having has to do with my boat lights. With every switch I turn on the lights get dimmer. I.E Lights are on and I turn on the livewell pump/s they dim, if I turn on the bilge they dim even more. They were very dim when the motor was on and idling. Once I got on the throttle they brightened up. Not 100% sure where to start looking.

I’d start by having the cranking battery load tested.

Most outboards do not deliver full rated amps from their charging system until the engine is throttled up. Some engines' designs deliver very little at idle. All the things you describe point to a charging system that kicks in when you throttle up (indicating the charging system is probably operating as intended), but that you have a marginal battery. You didn't mention what size battery you have, but you might consider moving up in size & specs when you replace it. Many boats are operating with a battery that's undersized for all we ask it to handle. Do you regularly charge the main battery immediately after fishing trips? We often don't run the outboard long enough to replace energy we use from the battery, so it will be abused over time if you aren't charging it.

I charge it every time I come off the water and it stays on the charger. I will check the water levels in the battery. It is an Everstart 24ms2 1000 Marine cranking amps 135 amp hrs. I will probably start looking at connections to see if I can find a bad ground or bad connectors.

Resistance in a connection will dim lights also. If the battery checks out good. Check your battery connection. There will be a relay feeding your distribution panel Or should be?? Mine has one. Just have to hunt the bad spot.

A relay? You possibly mean a circuit breaker?

I do not believe that a Group 24 battery is a 135AH rated battery. Even good Group 31 batteries (which are monterous compared to a Group 24) is typically rated as 105-115AH. I view a Group 24 as inadequate for a bass boat. if that battery is at end of life, you should use this opportunity to up-size to a more proper choice. Get a hydrometer at auto parts store and check battery cell electrolyte after 12 hours of charging. It typically will show you if you have a failing cell, which is what I suspect in this case.

P.S.: I looked at walmoart's website (which is in contention for the worst website in the world) and they do show that Group 24 battery as having 135AH. I absolutely do not believe that -it's an error. In comparison, looking at the Group 31 Deep cycle battery on Sam's Club's website, I see it has an AH rating of 105. Your battery was actually inadequate from the get-go in my opinion.

Ok, my Mercury calls for 1000mc/750cc amps. I only have one graph that I run, an 1198. The only other things I would have on at the same time MIGHT be bow/stern lights, bilge pump, and livewell pumps (2).

Should I be looking at a dual purpose battery versus just a starter battery?

The low amp loads you may have all contribute to draining the battery, not just the most things you might have on at one time. Those loads also only matter when the outboard is off. When you have it running at anything above idle, you're not draining the battery.

That Mercury 1000 MCA requirement rules out a lot of batteries. (I have the same issue.) Here's a honker of a battery at a fair price that will make your troubles go away for a long time. It meets the MCA spec and has a lot of DC reserve minutes to insure you don't run it down very easily. You'll need space for a larger battery, and a Group 31 battery tray. Amazon has the trays if you like to shop there.

Sam's Club Group 31 AGM Battery

I had the same problem except my 2 Helix's would shut down. Running a 24. I went with a 29 only because a 31 wouldn't fit. So far, so good.

A 31 series will not fit. I might be able to squeeze a 29 in there, but itll be tight and will have to remove the oil reservoir to get it in and out. I just need to find something with the correct Cranking amps.

If I find something that has the correct cc amps but low on the mc amps would that work? I believe I've hunted down a 770 cc but 930 mc. Thought? And no I have not gone through electrical components yet.

If you bought an agm battery you could lay it on its side. Would it fit that way? Or a lithium, they are much smaller.

I went to Academy and found a 31 series battery and I compared it with there 29 series and they were the same. I also found a 27 blue top. Both meet the cranking amp requirements. I am going to test fit my 29 TM battery to see if they would work a long with testing some connections before I commit to spending $230+.

The length is what's iffy.

MCA = Marine Cranking Amps. This the a cranking amp rating that is derived at a worst case environment of 32 degrees F.
CCA = Cold Cranking Amps. This the a cranking amp rating that is derived at a worst case environment of 0 degrees F.

CCA is typically related to vehicle use and MCA is typically related to boating use. (Most don't do much boating below 32 degrees F.) Batteries have a harder time in cold temps, so an MCA rating is a way for a battery to get a better rating as the assumption is you'll always be above 32 F when you use it. Outboard manufacturers present MCA specifications for you to meet. so you should pay attention to the MCA, ignore CCA. You want the correct MCA as there's no correlation for CCA to your outboard.

I'd be tempted to run with the Sam's AGM in Group 27 if I were in a similar predicament of space issue. That battery will have good support for low amp loads, and has an MCA of 900. Remember amps go up with the temperature. A 900 MCA battery can deliver more than its min. rating with a rising ambient temperature. If you don't fish near 32 F much, it will likely crank just fine every time for a very long service life.

clean/tighten all grounds and especially the one at the battery.