OK, GM was [and still is, I believe] building the 2.5 liter and 3.0 liter engine in Mexico simultaneously. MerCruiser used the 2.5 [old 153 cubic inch Chevy II / Nova] block for a 120 hp motor and the modified 3.0 liter [183 cubes] engine with 4" bore as a 130, 135, and 140 hp rated motor. The...