Abstract: A muffler for exhaust gases is constructed with a small casing skirting a portion of an exhaust gas inlet pipe. The end of the casing nearest the exit port of the pipe is blocked and provided with a layer of sound absorbing material. The exhaust gases exiting the pipe turn within the layer and flow back up the outside of the pipe inside the casing and exit at a point near the upper end of the casing. The structure has sound arresting properties, particularly for high frequency sounds.

Abstract: A device for protecting the inlet or draft port of a water-jet propulsion system is disclosed. In a forward part of the inlet port of a drafting duct of a propulsion pump, a grate is mounted rotatable around a shaft which in turn is supported by a bracket. The bracket is secured to a lower part of the pump casing. A pin, passing through the grate, is urged by a spring to engage a part of the bracket to lock the grate in a position to block large objects from entering the duct. When the pin is disengaged against the force of the spring the grate is rotated to a position to permit manual entry into the duct for repair purposes.