Blue Sea Systems 7720-BSS AMI/MIDI Safety Fuse Block with Clear Cover, 200A, 32VDC

Current Rating: 200A
Fuse Holder Type: Fuse Block
Fuse Type: MIDI / AMI
Number of Circuits: 1 Circuit
Termination: M8
Voltage Rating: 32VDC

Disconnect Power: Always disconnect the negative battery cable before starting.
Mount Base: Secure the fuse block base using appropriate M6 fasteners.
Prepare Wires: Crimp high-quality M8 (5/16") ring terminals onto your power cables.
Install Fuse: Place your AMI or MIDI fuse onto the block and secure it using the M5 screws to 27 in-lb.
Connect Cables: Attach ring terminals to the M8 studs and tighten to 120 in-lb.
Secure Cover: Snap the sealed cover into place. It includes a tether to prevent loss and storage for one spare fuse.
Installing the Blue Sea Systems 7720 Safety Fuse Block requires attention to specific torque settings and mounting orientations to maintain its IP66 and ignition protection ratings.
Location: Install in a readily accessible spot as close as possible to the battery to minimize unprotected cable runs.
Orientation: While it can be mounted in any direction, vertical orientation is recommended by SVB Marine to best shed moisture.
Hardware: Use 1/4" (M6) screws for mounting the base to a bulkhead or panel.
Ignition Safety: Because it is ignition protected (ISO 8846 / SAE J1171), it is safe for use in gasoline engine compartments where explosive fumes may be present.
Wire Size: To reach the full 200A rating, you must use 2/0 AWG (70 mm²) or 4/0 AWG cable, depending on the specific application requirements.
Studs & Screws:
Terminal Studs: Use M8 (5/16") ring terminals.
Fuse Screws: The block uses M5 x 0.8 stainless steel screws to secure the fuse.
Cover Breakouts: The insulating cover features breakouts that allow wires to exit in three different directions, protecting against accidental shorts regardless of entry point.

The "Stack-Up" Rule
To prevent high resistance and dangerous heat buildup, follow this specific order when mounting your cables to the M8 (5/16") studs:
Bottom: Place the ring terminal directly against the fuse block base.
Middle: Place the AMI or MIDI fuse on top of the ring terminal (or between two terminals if connecting two wires).
Top: Secure with the washer and nut, and torque to 120 in-lb.

Why it matters: Putting a washer between the terminal and the fuse creates a "bottleneck" for current, which can cause the connection to get hot enough to melt the housing, even if the fuse hasn't blown.