decompression lever

[John Mercator]

I am trying to figure out when the decompression lever is open or closed on a 1983 Universal M 25 Diesel. In the down (toward boat midline) position or up (more toward the port side of the boat). I have assumed that it was down. I never use it and on a recently aquired 1983 Cat 30 I noticed that I have been running the engine and the lever is up, so perhaps my assumption that down was closed is wrong??? The manual pics that I have doesn't give a clear description of the position. If I have been running the engine in the open position (that is the position one uses to decrease the compression for starting) what damage should I expect has been done? Thank you for any definitive responses. John

 

[Chris]

The decompressor

on a diesel opens the exhaust valve enough to permit cranking the engine over by hand. The engine will not fire on the decompressed cylinder until the lever is returned to the run position. You will not do any damage because the engine won't run decompressed (no compression=no bang=no run). With electric start, most modern engines do not require decompression to start. With a hand crank, you decompress, crank like a fool as fast as you can buiding up revs and flywheel momentum, then flip the lever to run and the motor fires up...you hope.