Mercury F1AZ-6303-ARM Crankshaft Assembly

Crankshaft installation is the first step in engine reassembly. The engine is flipped upside down, main bearing caps are removed, and new bearing inserts are placed. The crankshaft is carefully positioned and oil clearance is checked. The caps are installed and torqued in three steps. Grease is applied to the bearing surfaces and the crankshaft is placed back into the block. Crankshaft rotation and endplay are checked. For OHC engines, jack screws are used and the rear main oil seal is installed.

Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks.

Using a micrometer, measure the diameter of the main and connecting rod journals and compare the results. Measure the diameter at several points to detect taper and out-of-round conditions, including measurements at each end of the journal near the crank throws.

Gently pry the crankshaft to the front and note the reading as the endplay. Alternatively, feeler gauges can be used for this purpose.

Check the main bearing caps to see if they're marked to indicate their locations. They should be numbered consecutively from the front of the engine to the rear. If they aren't, mark them with number stamping dies or a center-punch.

Install the rear main oil seal.