Distribution Blocks and Fusing

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.

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.

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?

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.