| 摘要 |
A marine propulsion unit comprises a cylinder (1), a combustion chamber (2) extending from one end of the combustion chamber, a spark plug (8) provided in the combustion chamber (2), and a piston (5) mounted for reciprocating movement within the cylinder (1). A first port (9) is provided in the combustion chamber (2), and this is selectively openable independent of the position of the piston (5) within the cylinder (1). If the propulsion unit should be immersed in water so that the cylinder becomes flooded, the cylinder can be purged by opening the port (9) and moving the piston (5) so as to expel water through the port (9). Once all water has been expelled, further movement of the piston causes gases in the cylinder to pass over the spark plug.
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