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Blue Sea 30-300A Marine Rated Battery (MRBF) Single Terminal Fuse
Blue Sea 30-300A Marine Rated Battery (MRBF) Single Terminal Fuse
High-Amp Protection - Mounts on 3/8" (Approx. M10) Battery Studs - Max 300A
Highlights:Protective Cover: Flexible red insulating cap helps prevent accidental short circuits,Terminal Stud: M8 stainless steel stud for secure fuse and cable attachment,Mounting Plate: Flat connection point for direct installation onto battery terminals,300A Capacity: Robust design capable of handling high-current loads up to 300A.
A Blue Sea MRBF fuse holder with a 75A fuse installed for demonstration. This compact design allows for high-current protection to be mounted directly on a battery post. Note that fuses are sold separately from the holder.
Technical drawing detailing the 5191 model dimensions, indicating a compact 60.9mm overall length, 20.0mm width, and 44.5mm vertical clearance for tight spaces.
Schematic diagram illustrating the correct assembly order: the block mounts onto a 3/8 inch (M10) battery stud, while the cable connects to the top M8 stud. 
Regular price
$45.00
Availability:
In Stock
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DESCRIPTION
Space-Saving High-Amperage Circuit Protection
*Please note Blue Sea fuses are manufactured by Eaton, Bussman or Ionnic and may have labelling of one of these manufacturers on the product and/or packaging.
The Blue Sea Marine Rated Battery (MRBF) Single Terminal Fuse Block solves one of the most common challenges in marine and automotive electrical installations: limited space. By mounting directly onto the battery terminal, this fuse block eliminates the need for short, difficult-to-install cable runs between the battery and a traditional firewall-mounted fuse holder. This design not only saves valuable room in crowded battery compartments but also reduces resistance and potential failure points in your high-current cabling.
Engineered for demanding environments, this unit is ideal for protecting high-load circuits such as inverters, windlasses, and bow thrusters. With a maximum voltage rating of 58V DC, it is perfectly suited for modern 12V, 24V, and 48V electrical systems found in boats, caravans, and off-grid 4WD setups.
Direct Battery Terminal Mounting
The primary advantage of the Blue Sea Marine Rated Battery (MRBF) Single Terminal Fuse Block is its ability to interface directly with the power source. It is designed to mount securely onto a standard 3/8" (Approx. M10) battery terminal stud. By fusing the circuit right at the battery post, you ensure maximum safety; if a fault occurs in the main cable running to your equipment, the fuse will blow immediately at the source, preventing potential fire hazards associated with unprotected live cables.
Versatile and Robust Design
Constructed with marine-grade materials, this fuse block is built to withstand the harsh conditions of the Australian outdoors. The hardware includes stainless steel studs and tin-plated copper bus bars for maximum conductivity and corrosion resistance. The unit features M8 (Approx. 8mm) studs for connecting your load cables, accommodating heavy-duty lugs and cabling required for loads up to 300A.
Safety is paramount in high-current applications. The included insulating cap prevents accidental shorts across the conductive terminals, satisfying ABYC/USCG requirements for insulation when installed correctly. The versatile design allows for flexible cable orientation, making it easier to route heavy gauge wire in tight lockers.
Single Circuit Simplicity
This model features a compact single-terminal design, perfect for dedicating a fused line to a specific high-load device or a main DC distribution panel where footprint minimization is critical.
Key Features
- High Interrupt Rating: Safely handles high amperage loads up to 300A.
- Compact Footprint: Mounts directly to 3/8" (Approx. M10) battery studs, saving panel space.
- Voltage Versatility: Rated for 58V DC, suitable for 12V, 24V, and 48V systems.
- Secure Connections: Uses M8 (Approx. 8mm) output studs for secure cable termination.
- Safety Cap: Insulating cap protects against accidental short circuits.
- Corrosion Resistant: Tinned copper and marine-grade stainless steel hardware.
Whether you are refitting a yacht or building a custom tourer, the Blue Sea Marine Rated Battery (MRBF) Single Terminal Fuse Block provides professional, reliable, and neat circuit protection exactly where you need it.
Secure your high-current electrical system today with this compact terminal fuse solution.
SPECIFICATIONS
Specifications
| Ignition Protected | No |
|---|---|
| Maximum Amperage | 300A |
| Maximum Voltage | 58V DC |
| Terminal Stud |
M8 (5/16") (M8 major diameter 8 mm; 5/16" ≈ 7.94 mm; reference only) |
| Maximum Torque |
75 in-lb (8.47 N·m) (approx. 6.3 ft-lb; reference only) |
| Weight (min / max) |
0.16–0.16 lb (0.07–0.07 kg) (approx. 73 g; reference only) |
| SKU: | BS-5191B |
| Barcode: | 632085051914 |
| Model #: | BS-5191B |
| MPN: | BS-5191B |
WARRANTY
Blue Sea Warranty Policy
Blue Sea Systems products sold by us are supplied with a warranty against defects for the warranty period shown below, subject to the product type, application and the terms of this warranty policy.
The express warranty provided by us is limited to a maximum of 5 years from the original date of purchase, unless otherwise required under Australian Consumer Law.
Blue Sea Systems may offer longer manufacturer support on some products at their discretion
Warranty Lengths by Product Range
| Blue Sea Product Range | Warranty Length | Application / Notes |
|---|---|---|
| Most Blue Sea Systems Products | 5 years | Applies to most Blue Sea Systems products found to be defective in materials or manufacture. |
| P12 Battery Chargers | 5 years | Warranty period starts from the original date of purchase. |
| P12 Remote Displays | 5 years | Warranty period starts from the original date of purchase. |
| Digital Meters | 3 years | Warranty period starts from the original date of purchase. |
| Vessel System Monitors | 3 years | Warranty period starts from the original date of purchase. |
Warranty Assessment and Remedy
If a Blue Sea Systems product is found to be defective in materials or manufacture within the applicable warranty period, we will, at our discretion, arrange a repair, replacement, store credit or refund, depending on the nature of the fault and the requirements of Australian Consumer Law.
Products may need to be returned for assessment before a warranty claim can be approved. Where required, the product must be returned with dated proof of purchase and a clear description of the fault.
Labour costs for removing, replacing, reinstalling or diagnosing a product are not covered by this express warranty unless otherwise required under Australian Consumer Law.
Making a Warranty Claim
To make a warranty claim, please contact us with your dated proof of purchase, product details and a description of the fault.
The product may need to be returned for inspection before the claim can be assessed. If the product is confirmed to be faulty and covered by this warranty, we will advise the available remedy.
What This Warranty Does Not Cover
This warranty does not cover faults or damage caused by incorrect installation, incorrect application, misuse, abuse, neglect, unauthorised modification, accidental damage, normal wear and tear, environmental damage, or failure to use the product in accordance with the manufacturer's instructions.
- Incorrect installation or wiring
- Incorrect product selection or application
- Misuse, abuse or neglect
- Physical or accidental damage
- Water ingress or environmental damage outside the product's intended use
- Unauthorised modification or repair
- Normal wear and tear
- Labour costs for removal, replacement, reinstallation or diagnosis
- Freight, travel or call-out costs unless otherwise required by law
- Products not returned for assessment when reasonably required
Manufacturer Support
Blue Sea Systems may provide additional manufacturer support on some products beyond the warranty period listed above. Where available, we may assist customers in contacting the manufacturer, but any manufacturer support beyond the express warranty period is subject to the manufacturer's own terms and continued availability.
Australian Consumer Law
This warranty is in addition to other rights and remedies available at law. Our goods come with guarantees that cannot be excluded under the Australian Consumer Law. You are entitled to a replacement or refund for a major failure and compensation for any other reasonably foreseeable loss or damage. You are also entitled to have the goods repaired or replaced if the goods fail to be of acceptable quality and the failure does not amount to a major failure.
