Mercruiser 4 Cylinder Engine Coupler | Sierra 18-2321Mercruiser 4 Cylinder Engine Coupler Sierra 18 2321 SIERRA Engine Coupler 18 2321 Engine coupler fits late model Mercruiser GM 4 cylinder engines with triangular style engine coupler. This triangular style engine coupler is for GM 4 cylinder engines with late style, small crankshaft bolt pattern Fits Mercruiser model 3. 0LX engines from 1994 to 1998 with serial number range F000001 L096999 This is the same as the 18 2195 without the yoke shaft