Blanking plug replaces B744V insert, seals hull with self-closing valve; secure with pin and wire to keep bilge dry during storage, haul-out, or fouling checks. Read more.
This plug takes the place of the B744V’s speed/temperature insert whenever you pull the sensor, whether for cleaning, long-term mooring, or winter storage, so the thru-hull stays watertight and the paddle-wheel cavity stays free of fouling. A spring–loaded flap inside the housing snaps shut as soon as you withdraw the insert, cutting the flow to a trickle while you fit the plug.
Fits only B744V-series bronze housings. The plug is made for the standard-length B744V and long-stem B744VL assemblies; it will not secure in other Airmar models unless they share the same quarter-turn lock and stem length.
You still need the insert nut and safety wire. The self-closing flap is a flow restrictor, not a watertight seal. The plug must be locked in place with the insert nut and laced with the safety wire every time you use it.
O-rings must be intact and greased. Inspect the two O-rings on the plug; replace any that are nicked and coat them with silicone grease or petroleum jelly before insertion to ensure a proper seal.
When to swap the sensor for the plug:
Boat will sit in salt water for more than a week
Vessel is being hauled or stored ashore
Speed or temperature readings suggest marine growth on the paddle-wheel
Simple installation: pull the safety wire, unscrew the insert nut, withdraw the sensor, align the arrow on the plug toward the bow, push-twist until the keys seat, hand-tighten the insert nut, and re-rig the safety wire.
Protect the plug itself. If it will remain in the hull for weeks, coat the section below the lower O-ring with a water-based anti-fouling paint made for transducers.
TIP: Keep the blanking plug in a labelled bag next to the thru-hull so it’s always ready when it’s time to service the sensor.
