TheJOHN A. RYDER, clam dredging research vessel of the Maryland Department of Research and Education, was converted from dual-engine to single-engine powering of the pumping and propulsion systems through use of a controllable-pitch propeller designed for the specific application by Electric Boat Division of General Dynamics Corporation. The dredge pump is driven by mechanical power take-off from the propulsion engine at any desired speed, and optimal thrust is obtained by adjustment of the controllable-pitch propeller. Tests conducted by the Department of Research and Education before and after conversion included (1) cruising speed and fuel consumption at cruising speed, (2) dredging rates, and (3) fuel requirements of dredging. Performance of the controllable-pitch propeller at cruising speed compares favorably with that of the fixed-pitch propeller formerly used. Fuel savings of about one-third are realizable with the single-engine powering system, with no sacrifice of necessary flexibility of operation.