Actually that's somewhat incorrect. The fuse block is correctly located but the wrong type for marine use.
Fuses are there to protect the boat and wiring, not to protect the amp or battery. The fuse should be as close as feasibly possible to the AMP, not the battery. That way if the amp malfunctions and draws too much current, the fuse will pop before it can cause a melted power cable or overload the battery, both of which can cause a fire.
The fuse needs to be sized for the max draw of the amp, not the wire gauge. The wire gauge needs to be sized for the load it is expected to carry otherwise it's a fire hazard. While a fuse near the battery will protect the wire (if both wire and fuse are properly sized), the purpose is to prevent the wire from bursting into flames regardless of proper sizing, and the only way to do that is to fuse the AMP so it CAN'T draw too much current through the wire, properly sized or not. This applies to ANY electronic device added to a boat, car, truck, etc.
The fuse needed should be an ANL or similar fuse which is rated for marine use near ignition sources such as fuel tanks and hydrogen producing batteries. An AGU fuse is basic glass and NOT rated for ignition protection which means if it pops, it could spark and start a fire.
I hear this misinformation again and again about fuses and what they protect and how to install them...I don't know where it started, but it's bad information which continues to be spread.
@slaubman Yes that is a fuse block for cars, not marine use. While the plastic housing could prevent a spark if the AGU fuse blows, it's not rated to do so which means it's a fire hazard. There's a reason why marine rated items cost more - they're much safer than the standard items used for car stereo systems which typically don't need the extra safety measures.
