Engine information

[JLemons]

One of the things I like to do when viewing what is currently for sale online is also look up the registration information on FlightAware and see if the aircraft has flown recently. I also look at the registration information and for the engine information I see this: CONT MOTOR IO-360 SER (Reciprocating) Horsepower: 300. Not sure what the SER means and why do they list horsepower as 300? The exact thing is shown for every tail number I look up.

James