Abstract: A marine propulsion water jet system which operates at high efficiency and automatically adjusts itself to maintain a relatively constant primary injection water velocity over a wide speed range. The propulsion system includes a fluid flow amplifier by which a high velocity principal water flow is injected into a slower velocity secondary water flow to form a water jet. The fluid flow amplifier includes an adjustable orifice through which the principal water flow is injected into the secondary water flow and the size of the orifice is automatically adjusted in order to maintain a relatively constant water jet velocity.

Abstract: A molten metal treatment apparatus comprising a passage of predetermined size and length for receiving superheated molten metal from a source thereof, and for supplying the molten metal for subsequent casting; a gas inlet and a control valve for controlling the velocity of the molten metal through the passage by exposing the molten metal to a source of pressurized gas; a cooling jacket at least partially surrounding the passage for controlling the temperature of the molten metal within the passage between predetermined upper and lower limits for forming a thin solidified shell having a molten metal core within the passage; the combination of the velocity of molten metal and the temperature of the molten metal within the passage for allowing dendrites to grow into the molten core from the solidified shell, and for breaking off portions of the dendrites and entraining them in the molten metal thereby producing a solids content within the molten metal for subsequent casting.