Head to head
Class-T 400A vs MRBF 300A Marine Battery Fuses
Both do the same job. The question is which one your boat is actually asking for — and on this site that is a number, not a preference.
| Blue Sea Systems Class-T 400 A | Blue Sea Systems MRBF terminal 300 A | |
|---|---|---|
| Fuse rating | 400 A | 300 A |
| Price band | $130–$210 | $45–$80 |
| Best suited to | 400 Ah and larger banks with a substantial inverter. | Protecting individual charge sources and feeds close to the battery. |
| Look elsewhere if | Your cable cannot carry 400 A — the fuse must protect the cable, not the battery. | You are considering it as the main bank fuse — its interrupt rating is not the Class-T's. |
Blue Sea Systems Class-T 400 A
The size most cruising boats end up at once a 2000 W inverter is on the bus.
Blue Sea Systems MRBF terminal 300 A
A terminal-mount fuse for the branch circuits, not a substitute for the Class-T at the bank.
Sized for your boat
400 A
Fuse rating for a 400 Ah bank
A starting point, not a specification. The correct fuse rating comes from the cable you actually run and its length, not from the bank alone. Have a suitably qualified person check the design against AS/NZS 3004.2 and the licensing rules that apply to your vessel and jurisdiction.
Closest rating we list
The honest answer
Size it first, then choose.
A head-to-head between two ratings is the wrong question if neither matches your boat. Work out what the boat needs, then pick between whatever meets it — which is usually a decision about support and documentation rather than about amps.
Before choosing Blue Sea Systems Class-T 400 A and Blue Sea Systems MRBF terminal 300 A
Fuse interrupt ratings and cable protection
A fuse or switch is selected for its role in the actual circuit. Physical fit and the printed current rating do not establish suitability for the available fault current, voltage or connected cable. Ask for the protection schedule in the final system documents and obtain the exact approved spare part numbers before remote travel.
Confirm specifications against the exact model and revision offered by the supplier. A listed price band is a planning reference; request a current written quote with installation and commissioning separated from equipment supply.