Raymarine ST600/B120 Speed & Temperature Through-Hull Transducer, For Analog Instruments, Bronze, Retractable, 45 ft Cable

Overview

The Raymarine M78716 is a bronze through-hull speed and temperature transducer for Raymarine analog instrument systems. It measures speed through the water and water temperature from a low-profile hull fitting, making it a practical replacement or upgrade for boats running compatible Raymarine instrument displays.

The unit uses a 2-inch bronze through-hull fitting and a 15 m cable, equal to 45 ft, with ISO female spade connectors. It is suitable for fiberglass and wood hulls, which makes it a common fit for sailboats and powerboats where a bronze fitting is preferred below the waterline.

This is an instrument transducer, not a CHIRP fishfinder transducer. It is built for speed and temperature data on compatible Raymarine systems, including i40 Speed, i50 Speed, iTC-5, ST60, ST60+ Speed and legacy analog instruments.

Key features

• Bronze through-hull speed and temperature transducer for Raymarine instrument systems.
• Low-profile hull fitting helps reduce drag compared with taller external fittings.
• Retractable core allows access for cleaning and maintenance when marine growth affects paddlewheel readings.
• 2-inch through-hull installation size for compatible fiberglass and wood hulls.
• 15 m cable, equal to 45 ft, supports routing from the bilge or hull area to the instrument location.
• ISO female spade connectors for connection to compatible Raymarine analog instrument wiring.
• Works with compatible Raymarine analog instruments such as i40 Speed, i50 Speed, iTC-5, ST60, ST60+ Speed and legacy systems.

Compatibility and fit

This transducer is a good match for boats that need speed-through-water and water temperature data rather than GPS speed alone. It is especially useful on sailboats where true wind calculations, performance sailing data and current-aware navigation depend on accurate water speed input.

Before ordering, confirm that the existing instrument system accepts this analog speed and temperature transducer style and that the hull material is fiberglass or wood. For ST70-style installations, a compatible speed pod or interface may be required between the transducer and the instrument network.

Installation and setup

The M78716 installs through the hull and requires a 2-inch hole. The 45 ft cable gives enough reach for many typical runs from the hull fitting to the display or interface location, but routing should be checked on the boat before installation, especially on larger vessels or where cable paths must avoid machinery spaces.

As with any below-waterline fitting, installation should follow proper marine sealing practice and be placed where the transducer has clean water flow while staying clear of turbulence from strakes, intakes, keels, propellers and trailer bunks. The retractable insert is useful for seasonal cleaning, since paddlewheel speed readings can be affected by fouling.

Use cases on board

This transducer suits owners maintaining Raymarine ST60 and related analog instrument systems, as well as boats using i40 or i50 speed instruments that need a bronze through-hull sensor. It is also useful for sailboats that rely on speed-through-water data for trim, polar performance and wind calculations.