The connecting rod is the connecting link between the piston and the crankshaft. It is one of the most highly stressed parts of an engine in that the connecting rod transmits the forces of combustion to the crankshaft.

In general, the type of connecting rod used in an engine depends on the cylinder arrangement and the type of engine. Several types of connecting rods have been designed. Only two, however, the conventional rod and the fork and blade rod, are those likely to be found in marine engines used by the Navy and are the ones discussed here.

Figure 4-17.Cutaway view of a connecting rod showing oil passages (Colt-Pielstick).