Day Depth Charge Marker Mk 1 Mods 1 and 2

Over-all length, inches

Diameter, inches

Weight, pounds

Weight of dye, pounds

Weight of bursting charge, grams

Effective releasing altitude

Visibility

3,000 yards from deck of ship
5 miles from aircraft

Use: The marker is used to indicate the initial point of contact with submarines and provide a reference point for further search and attack during day operation.

Description: The marker consists of a circular wooden block on which is mounted a grenade-firing mechanism with a 15-second delay. Flourescein dye is contained in two cylindrical paper cans, one attached to each flat side of the wooden block; and a cellu-loid tube containing the black powder bursting charge is attached to the delay element and extends through the wooden block into the paper cans. The dye is rusty red in color when dry, but a water solution of the dye is yellow-green.

Operation: The operator clasps the marker firmly in one hand, being sure that the re-lease lever is held against the body of the marker. With the other hand, he pulls the safety ring which is attached to the safety cotter pin and launches the marker by throw-ing it over the side. When the marker is released, the spring-loaded striker forces the re-lease lever off. The striker, rotating about a hinge pin, hits the primer that ignites the 15-second delay fuse. The delay gives the marker sufficient time to reach the water and float on the surface, and then ignites the bursting charge. The gases evolved from the charge burst the dye containers and spread the dye on the water, forming a yellow-green slick about 40 feet in diameter. The slick lasts for 45 to 60 minutes.

Figure 185. Depth Charge Marker Mk 1 Mod 1