Raymarine ST900/P17 Speed/Temp Long Body Thru-Hull Transducer, For i40, i50, iTC-5, Plastic Housing, Low Profile, 10m Cable

Overview

The Raymarine E70687 is a ST950/P17 speed and temperature transducer with a plastic low-profile thru-hull housing and a 10 m cable for connection to compatible Raymarine instrument systems. It uses a Gen2 paddlewheel sensor for boat speed and a fast-response water temperature sensor, giving helm displays the two readings many sailors and powerboaters rely on for trimming sails, checking current, monitoring performance, and logging real speed through the water.

The P17 housing mounts through the hull and sits nearly flush, with only 5 mm extending outside the hull to help limit drag. The installation uses a 51 mm hole size and is suited to fiberglass and metal hulls. Speed reporting starts as low as 0.3 knots and remains smooth up to 45 knots, while the temperature range covers -10 to 40 degrees C.

This is an analog transducer for Raymarine i40, i50, iTC-5, and compatible legacy instrument setups. Its retractable insert allows the paddlewheel to be removed for cleaning or service, and the housing includes a valve assembly to help reduce water entering the bilge during routine maintenance.

Key features

• Speed and fast-response water temperature sensing in one thru-hull instrument transducer.
• Gen2 paddlewheel reads from 0.3 to 45 knots, which helps at low sailing speeds and during faster powerboat operation.
• Plastic P17 low-profile housing extends only 5 mm outside the hull to reduce drag compared with bulkier housings.
• 51 mm thru-hull installation for fiberglass and metal hulls.
• 10 m cable gives practical routing length for many helm, instrument pod, and electronics locker layouts.
• Analog output works with Raymarine i40, i50, iTC-5, and compatible legacy instrument systems.
• Retractable insert helps make paddlewheel cleaning easier while the boat is in the water.
• ST950 insert can retrofit into existing Airmar P17 and B17 housings where the installation matches.

Compatibility and fit

This transducer is a good match for boats using Raymarine instrument displays or an iTC-5 converter where analog speed and temperature data is required. It is especially useful on sailing yachts that need accurate speed-through-water information for wind calculations, polar tracking, race starts, and sail trim, as well as cruising and fishing boats where water temperature and real hull speed are useful at the helm.

Before installation, confirm the existing instrument system accepts an analog speed and temperature transducer and that the hull location has clean water flow across the paddlewheel. Avoid mounting behind strakes, intakes, through-hulls, or other fittings that can create turbulence and unstable readings.

Installation and maintenance

The low-profile thru-hull housing should be installed in a location that keeps the sensor submerged and exposed to smooth water flow across the hull. The 10 m cable should be routed away from sharp edges, heat sources, and high-current wiring where practical, with enough service loop to remove or inspect the insert without straining the cable.

Because paddlewheel sensors sit in the water, routine cleaning matters. Growth, paint buildup, or debris around the wheel can affect low-speed response and accuracy. The retractable design lets the insert come out for cleaning, while the housing valve helps limit bilge water during normal service.

Use cases on board

On a sailing boat, this transducer supports speed-through-water data used for apparent wind calculations, trim decisions, and comparing boat speed against target numbers. On a cruising or fishing boat, it adds water temperature and speed information without requiring a larger sonar transducer or network sensor package.

The unit is most suitable for owners replacing or upgrading an analog Raymarine speed and temperature sensor, or for refits where a low-profile plastic P17 thru-hull housing and a 10 m cable suit the hull and instrument layout.