Mercury F1AZ-6303-ARM Crankshaft Assembly

Inspect the endplay using a dial indicator or feeler gauges before taking out the crankshaft. If the endplay is more than the limit, then check for wear on crankshaft thrust surfaces. If necessary, label and number main bearing caps. On OHV engines begin from the center and loosen main bearing cap bolts gradually. In order to take off the crankshaft in OHC engines, follow this exact process. Replace main bearing cap bolts and lift out the crankshaft gently. Put back the caps in their original positions on the engine block and finger tighten their bolts.

Remove burrs from crankshaft oil holes with stone/file/scraper. Chamfer oil holes to prevent bearing damage. Clean crankshaft with solvent and compressed air. Use brush to clean oil holes and flush with solvent. Rub penny on journals to check for copper embedding. Inspect for wear, scoring, pits, cracks. Magnaflux for hidden cracks. Measure journal diameter with micrometer for taper/out-of-round. Regrind if damaged/worn. Check oil seal journals for wear/damage. Repair or replace if necessary. Examine bearing inserts.

After verifying the main bearing oil clearance, a thin, uniform layer of moly-base grease or engine assembly lube is applied to the bearing surfaces of the crankshaft.

Install the jack screws into the main caps and bottom them lightly against the caps. This must be done before the caps are placed into the block.

Rubbing a penny lengthwise on each journal will reveal its condition. If copper rubs off and is embedded in the crankshaft, the journals should be reground. If a journal picks up copper from the penny, it's too rough and must be reground.

Bottom all jack screws (which are 8 mm, Allen head screw, with left hand threads) against the main bearing caps.

Check crankshaft endplay again and verify that it is correct.

If a dial indicator isn't available, feeler gauges can be used. Gently pry or push the crankshaft all the way to the front of the engine. Slip feeler gauges between the crankshaft and the front face of the thrust main bearing to determine the clearance.

Using a micrometer, measure the diameter of the main and connecting rod journals and compare the results to the Chapter's Specifications. Measure the diameter at several points to detect taper and out-of-round conditions. Take measurements at each end of the journal, near the crank throws, to determine if the journal is tapered.

Check the oil seal journals at each end of the crankshaft for wear and damage. If the seal has worn a groove in the journal or if it's nicked or scratched, the new seals may leak when the engine is reassembled. An automotive machine shop may be able to repair the journal by pressing on a thin sleeve, but if repair isn't feasible, a new or different crankshaft should be installed.

The crankshaft can be removed only after the engine has been removed from the vehicle. It is assumed that the flywheel or driveplate, vibration damper, timing chain(s) or gears, oil pan, oil pump, and piston/connecting rod assemblies have already been removed.

Carefully lift off the main bearing caps, keeping them in order without disturbing the Plastigage or rotating the crankshaft.