Marine propulsion unit and a valve for a marine propulsion unit

A marine propulsion unit comprising:

• a cylinder;
• a combustion chamber extending from a first end of the cylinder;
• a spark plug disposed within the combustion chamber;
• and
• a piston reciprocably moveable within the cylinder;
• wherein the unit further includes a user-operable valve, the valve being selectively openable independent of the position of the piston within the cylinder, the valve being positioned such that, in its open state, movement of the piston causes gas within the propulsion unit to flow over the spark plug and subsequently to flow out of the propulsion unit through the valve;
• wherein the valve includes
• a valve body having an end face and a wall extending from the end face, an aperture being defined in the end face;
• and
• a valve stem moveable within and with respect to the valve body, the valve stem having a sealing portion located within the valve body in both an open state and a closed state of the valve, wherein, in the closed state of the valve, the sealing portion of the valve stem abuts against an inner surface of the end face and thereby closes the aperture;
• wherein a maximum width of the valve stem is greater than the width of the aperture in the end face of the valve;
• and
• wherein in the open state, the sealing portion of the valve stem is spaced apart from the inner surface of the end face of the valve body by a sufficient distance to permit water to drain from the cylinder through the valve.