In a piston engine, the main bearings are the bearings on which the crankshaft rotates, usually plain or journal bearings. The bearings hold the crankshaft in place and prevent the forces created by the piston and transmitted to the crankshaft by the connecting rods from dislodging the crankshaft, instead forcing the crank to convert the reciprocating movement into rotation.

Genuine 4BT series marine engine

Original 6BT series marine engine

Brand new ISF3.8 series engine

NTA855 engine

4JB1 engine

QSB6.7 enginee.

Injector

Piston kit

Connecting rod

Main bearing

Cylinder liner

Turbocharger