Welcome to the forum and airplane ownership. I too have a 1980 152. Mine was built in Nov 1979, about 3 months and 200 serial numbers behind yours. Mine was owned by a local flight school, so it has close to 10000 hrs on the airframe.

My plane cruises at 2450 rpm, and gets 97 KIAS at 2500' MSL. Unless you have a cruise prop, your numbers seem to be high. I'd check to see if the airspeed indicator and the tach rpm are correct. You can ask around your airport and see if somebody has an optical tach. That will tell you for sure if your mechanical tach is correct.

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