Overview

The Blue Sea Systems 8255 is a 500A DC / 50mV DC digital meter shunt used with compatible DC ammeters and multimeters to measure current in a boat DC electrical system. It creates a 50 mV full-scale signal for the meter, which lets you monitor current on higher-load circuits without sending that current through the instrument itself.

This is the shunt only, not a display meter. It suits battery-bank monitoring and other DC circuits where you want to see charge or load current at the panel. For continuous operation, the working guideline is up to 66% of rated current under normal conditions, with intermittent duty up to 300% for 3 seconds and 100% for 5 minutes.

The shunt uses a resistive manganin metal element and main M10 bolt connections. That makes it a practical choice where the meter is mounted remotely from the cable run being measured and the installation needs a known 500A / 50mV shunt ratio.

Key features

• 500A DC / 50mV DC shunt ratio for meters that read a 50 mV external shunt input
• 50 mV full-scale output for current monitoring on heavier DC circuits
• Continuous-duty guidance of 66% of rated current under normal conditions
• Intermittent-duty rating of 300% for 3 seconds and 100% for 5 minutes
• Resistive shunt with a manganin metal element and M10 main connection bolts

Compatibility and fit

This shunt belongs in a DC current-monitoring setup, not on its own. It fits meters built for a 500A / 50mV shunt input, including Blue Sea Systems models such as the 8236 DC Digital Ammeter, 8248 DC Digital Multi-Function Meter with Alarm, 1832 M2 DC Ammeter, and 1830 M2 DC Multimeter with SoC.

For a replacement job, the main checks are the shunt ratio, the current range of the circuit being monitored, and whether your cable lugs and mounting space suit the M10 connection hardware. Matching the 50 mV signal specification is what determines whether the meter will read correctly.

Installation and setup

The 8255 is typically mounted close to the circuit being measured so the heavy-current cabling can stay short and well supported. The meter sense leads connect to the brass fittings, while the main current path runs through the M10 bolt terminals.

It is best installed on a secure mounting surface inside an electrical space where connections can be inspected and re-tightened as part of routine service. Recommended torque is 7 in-lb for the brass fittings and 190 in-lb for the M10 bolts.

Use on board

This shunt makes sense on boats where current flow matters as much as voltage, such as house-bank monitoring or other higher-current DC feeds. It is a good match for owners adding a panel meter, replacing a failed shunt, or updating an older monitoring setup that already uses a 500A / 50mV standard.