A C150 pilot reported loss of power on initial climb and a return to the airport.

Narrative

Airplane was newly out of annual inspection; detailed preflight completed by PIC (Pilot in Command) with reference to checklists. Extended run up completed and passed with no noted insufficiencies. First lap right hand pattern to [Runway] XX with gusty winds uneventful with expected performance. After touch and go initially developed full power on runway and rotated for second lap in pattern. Engine developed full 2400 RPM expected then progressively decreased and settled around 2100 RPM just over departure end of run way. Aircraft was pitched for Vx and unable to adequately climb and eventually descending with increasing pitch angle. Pitch was adjusted for forward airspeed and PIC [requested priority handling] for partial power assuming failing engine; airspeed was gained and shallow left turn was initiated and uneventful although low left hand pattern was completed and priority was given by Tower to aircraft. On ground problem was unable to be reproduced immediately by pilot and airplane was taxied to hangar with appropriate managing parties of airplane alerted of issue.