On April 6, 2021, about 1130 eastern daylight time, a Beech A36, N18394, was substantially damaged when it was involved in an accident near Arcadia, Florida. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, after takeoff he reduced engine speed to 2,300 rpm at an altitude about 800 ft mean sea level (msl). Several minutes later, he noticed that the engine rpm had risen to 2,500 and the oil pressure was zero. The pilot attempted to return to the airport; however, the engine “locked and the propeller stopped turning.” The airplane was at an altitude of 1,700 ft msl and the pilot subsequently performed a forced landing to a field. According to the Federal Aviation Administration inspector who responded to the accident site, the airplane’s right wing and cowling were substantially damaged. There was oil streaking present on the left side of the fuselage. According to the engine logbook, all six cylinders were replaced about 8 months before the accident. The airplane accumulated about 61 hours between the maintenance performed and the accident. Examination of the engine revealed the engine was seized; no holes were found in the crankcase and the oil filter remained attached to the engine. The No. 4 spark plug was oily, the others were in normal wear condition when compared to a Champion Spark Aviation Check-A-Plug chart AV-27. Both magnetos were removed, actuated with an electric drill, and spark was produced at all terminal leads. The valve covers were removed, and valve movement was not observed on Nos. 2, 3, and 6. The propeller movement was limited. The Nos. 5 and 6 cylinders would not move. The engine was not made available for an additional, follow up examination.