Fellas,
Thanks for the responses!! I apologize in advance for the book below but I wanted to answer all the questions.
I apologize for not giving enough info in some cases. Here is a little background that should help answer some of the questions. The boat is a 21ft center console with a T-Top. The engine is a 200hp Mercury. I have 1 battery in the back of the boat in a compartment and the other battery is in the center console. The Fuse panel is mounted in the T-Top storage box since the lights, radios, etc... are mounted to the T-top. Ideally, I could move this down into the center console and make things easier (and I may). The switched breaker panel and the bus bars are under the center console. The battery switch and the rear battery are in the same compartment.
Why are you running your grounds to the fuse panel and not your negative bus bar? Great question! The only reason I was doing this is because of the location. Those items are mounted on or around the T-top so rather than having to run the wires down to the center console I ran them to the fuse panel in the T-top storage box.
Why a positive bus bar? Another good question! I have never really used a battery switch before so its fairly new to me. I figured it would allow me to run only 2 wires from the 1/2 piece of the battery switch. One straight to the engine and one to the bus bar to feed everything else.
Do you have an idea of components you plan to use? The components I plan to use are mainly what is listed. I do plan on installing a Lowrance HDS- 7 Touch unit but that should be straight forward after all the other stuff is done.
Why use fuses instead of inline breakers off your battery? To be honest I wanted breakers but went with fuses for the simple fact of space. I dont have much room for the breakers. I went with these style fuse block terminals since they mount right to the battery. https://www.amazon.com/gp/product/B0019ZBTV4/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
My question is why 4ga to the accessories? How long a run is it from the batteries to the engine & how big of an engine are you using? Good questions! The rear battery and battery switch will be right next to each other and the engine is of course right there also. Now the run to the second battery and the switches/fuse panel is a descent size run. If I had to guess it is about 8-10ft. I did 4ga just to make sure the pos bus bar got enough juice and for future growth.
I would save $$$ on fuses and only put 1 100amp fuse between the switch and the + bus bar and feed the engine from the bar. Ill be honest, I do not think there is a fuse or breaker on the engine currently nor do I think there was when it came from the factory 12yrs ago. I will have to take a good look at that and verify later because it should probably be protected.
Also - the grounding to the fuse panel doesn't look right - the panel might have lights on it to indicate if current is flowing, so those would need to be grounded, but that's not the same as a ground circuit for the accessories. Not 100% sure I am understanding what you are saying here. The fuse panel also has a negative bus on it and that is why its run the way it is. Here is the fuse panel. Hopefully its done right
https://www.amazon.com/Blue-Sea-Systems-Blade-Block/dp/B000THQ0CQ/ref=sr_1_1?ie=UTF8&qid=1406735815&sr=8-1&keywords=blue+sea+fuse+panel
The only problem I see is having the livewell tied to the same battery bank as the outboard. Usually, at least on most small-water fishing boats, you would isolate the two circuits so you don't accidentally over-draw your starter battery down, which I'm sure isn't as much of an issue with 2 batteries but still. Great point! I am not too worried about this as I will be running two batteries. If for some reason I drain 1 battery then I will hit the switch to the backup battery and be able to get back. Also, the motor has an alternator on it so ideally, it should get some kind of charge while the engine is running.
Livewell and no trolling motor, 2 radios? Offshore boat? Yall are on point with the questions and I like it! Sorry, the diagram didn't encompass everything. I do have a trolling motor but that has its own 2 batteries (Its 24v).
If you have this and didn't show it great, but I would add an automatic float switch between the (+) bus and the bilge pump JIC. Great point! I was thinking of hooking the bilge pump/float directly to the battery that way when I get home I can turn the switch to off and not have to worry about anything draining the batteries. Also, if I ever leave the boat on the water overnight I can turn everything off but the bilge pump will still work if the switch is off. I plan to hook the battery charger straight to the batteries also. If not to the batteries I will hook them to the corresponding 1 and 2 on the switch. (I know some people are sticklers for having very little attached directly to the battery.