I just purchased a 1995 Seaswirl with the Volvo Penta 4.3GLPHUB model motor. The Volvo Penta engine database indicates this motor was manufactured from 1994 to 1995, and is rated at 160 hp. The database indicates that other models of the Volvo Penta 4.3GL motor manufactured in 1995 (models PNCA, PNCB and PNCS) are rated at 190 hp. What is the difference in the motors that results in the 30 hp increase?