Overview

The Blue Sea Systems 1841 is a panel-mounted OLED temperature monitor for tracking up to four temperature points on board. It runs on 7 to 70V DC, reads from -40°C to 120°C (-40°F to 250°F), and shows data on a 55 mm x 28 mm display with Fahrenheit or Celsius readout.

This is a practical fit for boats that need local temperature data and alarms without relying on a multifunction display. It works well for engine exhaust monitoring and other onboard temperature checks where a dedicated readout at the helm, switch panel, or machinery space is easier to use. The unit also includes an 80 dB audible alarm and a 500 mA isolated MOSFET relay output for an external alarm or relay-triggered circuit.

Key features

• Monitors up to four temperature sensors from a single display
• 7 to 70V DC input range suits 12V and 24V systems and other higher-voltage DC installations
• Temperature range from -40°C to 120°C (-40°F to 250°F)
• Auto-dimming OLED display with a 55 mm x 28 mm viewing area
• Adjustable high and low temperature alarms with an 80 dB audible alert
• Isolated 500 mA MOSFET relay output for external alarm or relay-based control
• ABYC compliant for engine exhaust monitoring
• Surface, flat-panel, and 360 panel mounting options
• Unit face is IP66 when surface-mounted as directed

Compatibility and fit

This monitor is a strong match for refit and new-build installations where temperature needs to be watched in more than one place. On many boats that means exhaust temperature, engine room hot spots, refrigeration spaces, or other equipment areas where a local alarm matters more than network integration.

Mounting location matters. The face is IP66 only when the unit is surface-mounted according to the installation guidance, so that setup makes the most sense in exposed helm or cockpit panels. Flat-panel and 360 panel mounting are better kept in protected locations because the rear of the meter is not waterproof. The standard surface-mount cutout is 2.125 in (54 mm).

Installation and setup

The included sensor mix gives flexibility for different onboard locations, with submersible sensors for wet areas and high-temperature sensors for hotter points in the system. When using multiple sensors, keeping their negative leads terminated close to the meter's pin 1 helps avoid reading errors.

The relay output is useful when you want the monitor to do more than display data. It can trigger an external alarm or switch an external relay when a channel crosses a set threshold. That makes it a good fit for skippers and installers who want dedicated temperature monitoring with local warning capability at the panel.

What’s included

• M2 head unit
• Surface-mount bezel and cover
• Flat-mount bezel and clamp
• Mounting ring and mounting nut
• Surface-mount gasket and seal
• Connector and screwdriver
• Two submersible temperature sensors
• Two high-temperature sensors
• Mounting screws