Blue Sea Systems 5191 MRBF Terminal Fuse Block, Battery Post Mount, 30-300 Amp

The Blue Sea Systems 5191 is a terminal-mount fuse block built to hold a single MRBF (Marine Rated Battery Fuse) terminal fuse, giving you compact, high-amperage circuit protection right at the battery. It mounts directly onto a 3/8 inch (MN10) battery post, with one 5/16 inch stud for the outgoing wire connection, so it takes up minimal space in tight battery compartments. The block accepts MRBF fuses rated from 30 to 300 Amp (fuse sold separately), making it suitable for protecting high-current circuits such as DC main feeds, inverters, windlasses, and bow thrusters.

Rated for up to 58V DC and 300A per block, the 5191 is built for demanding marine electrical systems and is designed to be weatherproof, holding up in small open-cockpit boats and other exposed, harsh-environment installations. A snap-on insulating cap covers the live terminal connection to help prevent accidental shorts from tools or stray metal contact. When used with MRBF fuses, the block is ignition protected, meeting the safety standard required near gasoline engines and fuel systems. The compact housing measures 2.5 inches wide by 2 inches high and is molded from durable plastic to resist corrosion in the marine environment.

Specifications

• Brand: Blue Sea Systems
• Manufacturer Part Number: 5191
• Product Type: Terminal Mount Fuse Block
• Fuse Type Accepted: MRBF (MRBF Terminal Safety Fuse)
• Fuse Amperage Range: 30-300 Amp (fuse sold separately)
• Voltage, Max Operating: 58 Volts DC
• Current, Max Operating: 300 Amps per block
• Terminal Stud Size: 5/16 inch-18 (8 millimeters)
• Mounting: Battery post mount, 3/8 inch (MN10) post, mounting hole size 10 (5 millimeters) 3/8 inch
• Number of Poles: 1
• Number of Positions: 1
• Material: Plastic
• Dimensions: 2.5 inches wide x 2 inches high
• Weight: 0.16 pounds
• Ignition Protection: Ignition protected when used with MRBF fuses
• UPC: 632085051914

Frequently Asked Questions

What fuse does the Blue Sea Systems 5191 fuse block use? The 5191 accepts MRBF (Marine Rated Battery Fuse) terminal fuses ranging from 30 to 300 Amp; the fuse itself is sold separately.

How does the 5191 mount to the battery? It mounts directly on a 3/8 inch (MN10) battery post and provides a single 5/16 inch-18 (8 millimeter) stud for connecting the outgoing wire.

What is the maximum voltage and current rating of this fuse block? The Blue Sea Systems 5191 is rated for up to 58V DC and 300 Amps of current per block.

Is the 5191 fuse block waterproof? It is weatherproof and suitable for small open-cockpit boats and other harsh marine environments where the block may be exposed to moisture.

Is the 5191 ignition protected? Yes, the fuse block is ignition protected when used with MRBF fuses, making it suitable for installation near gasoline engines and fuel systems.

What circuits is the 5191 fuse block designed to protect? It is sized for high-current circuits such as DC main feeds, inverters, windlasses, and bow thruster wiring, where a compact, terminal-mounted fuse is needed close to the battery.

Does the 5191 come with a fuse included? No, the block itself ships without an MRBF fuse; the fuse must be purchased separately in the amperage needed for the circuit.

What are the dimensions and weight of the Blue Sea Systems 5191? The 5191 measures 2.5 inches wide by 2 inches high and weighs 0.16 pounds.

How many circuits can one 5191 fuse block protect? The 5191 is a single-position, single-pole block, so it accepts one MRBF fuse and protects one circuit.

Does the 5191 fuse block have any protection against accidental shorts? Yes, it includes an insulating cap over the terminal connection to help prevent accidental shorts from tools or stray metal contact.

What material is the Blue Sea Systems 5191 fuse block made from? The 5191 housing is made from plastic, chosen for its resistance to corrosion in marine electrical environments.