Distribution Blocks and Fusing

[Poison]

I’m replacing an amp in my boat pretty soon and I have some questions on fuses and wiring. What I have now is working fine, but I figured I would pull it all out anyway in the name of aesthetics because I haven’t broken anything yet this year and it’s already June.

What I really want to do is add distribution blocks to have a single terminal from the battery switch powering all of the stereo (2 amps, head unit, and EQ)…right now I have like 5 things on the common part of the Perko switch, so that thing is pretty much over-G’d and I want to clean it up.

My question pertains to fuses… I have a Kicker 700.5 powering cabin and sub, and I am installing a IX500.4 to power the tower speakers (found used very cheap, replacing stock Kenwood amp). So I was going to get a distro block that takes (1) 1/0 Ga Input and outputs (3) 4 ga. The manuals state that the 700.5 takes 1 x 90 Amp external fuse (near the battery) and the IX500.4 takes 2 x 50 Amp external fuses (one near the amp and one near the battery). There is also an option to get fused distro blocks. So now I am confused as to the order of fuses, blocks, and battery. I want this done right, so can somebody help me with what I need to buy to do this correctly?

I know I need one fuse at (near) the battery for the 1/0 wire. Should the amperage of this fuse be the total of the max amperage of both amps? (50 + 90 = 140A fuse?)

I also need one near the IX500.4 (according to the manual), so that will be near the amp but before the disto block right?

I already have the 90 amp breaker for the 700.5, is that still necessary and if so, where should it go?

Individually, I know how to do this properly, but adding the distro block is what is throwing me off.

[MLA]

To start with, you will need a main circuit protector for your trunk line, thats right off the switch termination. That 90A breaker will do just fine for that. Since the IX amp does not have a chassis mounted fuse, I would suggest a fused distribution block mounted close, keeping the branch line to the IX, short. A 50A fuse and 4ga cabling will do for the IX and an 80A or a 100A fuse and 4ga for the 700.5.

[Poison]

The 50A fuse to the IX and the 80A fuse for the 700.5 are in the fused distro block and not in addition to it right?

So for a dude who has slept several thousand times since my 1 EE circuits class in college, is that 90A fuse for the main circuit protector on the trunk line really enough for both amps, even if one of them by itself requires a 90A breaker? I realize they will probably not both reach peak amp draw simultaneously, but my instinct would say it should be bigger. I trust your expertise, so I guess I'm interested in the science?

[MLA]

No additional fusing. The 90A breaker protects the trunk line and the 2 fuses in the fused distribution block protect the short runs of 4ga. the 50A is also protecting the IX since it does not have its own on board fuse.