Your Cart is Empty

Circuit Breaker 300A Inline


Suitable for some winch installations, these inline breakers are rated to trip at 300 amp. They are marine rated so suitable for installation on boats, caravans, 4x4 and trucks including under-bonnet installations.

  • 300A Manual Reset Circuit Breaker

    These waterproof circuit breakers will detect high amperage draws exceeding 300 amps and will fail open. Users can easily reset them with the toggle of the manual reset lever. They feature a test button which breaks the circuit instantly isolating downstream appliances from the upstream power source.

    Being a true inline breaker these units don't require cable lugs to be fitted and rather simply insert the cable end directly into the breaker and tighten the grub screw to retain it.

    These breakers are ideal for protecting cables from loads exceeding 300 amps. The breaker will withstand short peaks over 300 amps but will generally break at the rated setting. The breaker itself is housed inside a quality high temperature plastic housing which helps to reduce the impacts of radiant heat from the surrounding environment altering the trip rating.

    We do not recommend these breakers for use with your 4x4 winch as these are generally rated to draw in excess of 400A. Users should consider a manual isolator switch for their 4x4 winch or a 500 amp fuse.

    These breakers are suitable for use with our boat winches under certain applications. Again your boat trailer winch is rated to draw up to 400 amps however for many smaller or lighter weight boats you are unlikely to exceed 300 amp draw. In these scenarios users many benefit from a 300 amp circuit breaker.

    Running a breaker, fuse or isolator is especially important with the boat trailer winch as the power cables are run a longer distance from the engine bay battery to the rear of the vehicle. If this cable was to short circuit as a result of rubbing or even in an accident, a fire could be started. A circuit breaker or fuse installed close to the power source (battery) will protect against these scenarios and protect the cable and vehicle. Refer to the user manual and recommendations provided with your boat trailer winch for further information on wiring. 

  • Specification Value
    Voltage 12-42 V
    Rating 300 Amps
    Cable inputs 0 AWG (1/0) 53.47mm2
    Operating environment Marine / Under-bonnet suitable
    Dimensions 68 x 83 x 35mm
  • Winch Owner's Manual 

    Grunter Boat Winch Owner's Manual

    ATV Winch Owner's Manual

    Winch Dimensions:

    'Mustang' 9,500Lb with 28m spool

    'Brumby' 10,000Lb high speed winch

    'Colt' 12,000Lb

    'Steed' 17,000Lb with 28m spool

    'Steed' 17,000Lb with 45m spool

    'Mule' 17,000Lb dual motor winch with 45m spool

    'Stallion'  25,000Lb winch with 30m spool

    Tow Truck Winch 20,000Lb

    'Grunter' boat trailer winches (Standard & HP Models)

    'Grunter' Boat Trailer Winch Mounting Bracket

    ATV Winch 4,500Lb

    ATV Winch 4,500Lb Mounting Plate

    Winch Control Box

    Wiring Diagrams:

    Dual Motor Winch Wiring Diagram

    Winch Solenoid Wiring Diagram

    Winch Weights:

    Winch Type Other 92ft (28m) Cable 92ft (28m) Rope 100ft (30m) Rope 100ft (30m) Cable 148ft (45m) Cable 148ft (45m) Rope
    ATV Winch 4,500Lb 15lb (7 kg) X X X X X X
    9,500Lb X 57lb (26 kg) 42lb (19 kg) X X X X
    10,000Lb (High Speed) X X 50lb (23 kg) X X X X
    12,000Lb X 66lb (30 kg) 50lb (23 kg) X X X X
    17,000Lb Single Motor X 60lb (30 kg) 50lb (23 kg) X X 88lb (40 kg) 57lb (26 kg)
    17,000Lb Dual Motor X X X X X 101lb (46 kg) 71lb (32 kg)
    Tow Truck Winch 20,000Lb X 100lb (45 kg) 66lb (30 kg) X X X X
    25,000Lb X X X 68lb (31 kg) 104lb (47 kg) X X

    Cable Data:

     Winch Type Cable Type Length Cable Size
    Grunter Boat Trailer Winches (All models)

    Positive (Power)

    7m (~23ft) 50mm²

    Negative (Earth)

    3m (~10ft) 32mm² 

    Control Box Cables

    Various <1m (< ~3ft) From winch to control box only.  25mm² 
    Grunter Cable Upgrade (Postive cable only)

    Positive (Power)

    10m (~32ft) 50mm² 

    4x4 Winches (All models)

    Mustang, Colt, Steed, Mule, Brumby, Stallion, Tow Truck winch models.

    Positive (Power)

    1.8m (~6ft) 25mm² 


    Negative (Earth)

    1.8m (~6ft) 25mm² 

    Control Box Cables

    Various <1m (< ~3ft) From winch to control box only.  25mm²
    4x4 Winch Cable Upgrade

    Positive (Power)

    3m (~10ft) 25mm²

    Negative (Earth)

    3m (~10ft) 25mm² 
    Big Air - Air Compressors (All models)

    Positive (Power)

    3m (~10ft) 16mm²

    Negative (Earth)

    3m (~10ft) 16mm²

Customer Reviews

Based on 2 reviews
Bryan Casey

Finally a winch breaker that works properly.
After trying 2 other breakers which failed under load I installed the breaker from Sherpa and it is awesome.

Great Circuit Breaker..

Bought this online at Sherpa and installed it in my caravan. Works perfectly and is a very compact unit.