807640 Mercruiser SCREW (5-1/2 IN.)

Start by:a. remove oil pumpb. remove oil pan plate 1. Remove the bolts and No. 1, 3, and 5 main bearing caps (1). Remove the lower halves of the main bearings from the main bearing caps.
If the crankshaft is turned in the wrong direction, the tab on the bearing will be pushed between the crankshaft and the bearing area in the cylinder block. This can result in damage to the cylinder block and/or the crankshaft.
On the center main journal that has no oil hole, put a thin piece of soft material that will not damage the crankshaft journal against the end of the bearing opposite the tab. Hit the bearing with the soft material until the tab of the bearing is free from the groove in the cylinder block. Remove the upper half of the main bearing. 2. Remove the upper half of the other main bearings as follows:a. Turn the crankshaft until tool (A) can be installed in the hole in the crankshaft journal. Install tool (A).b. Turn the crankshaft in the direction which will push the upper halves of main bearings (2) out, tab end first.c. Check the condition of the bearings. See Guideline For Reusable Parts, Main And Connecting Rod Bearings, Form No. SEBF8009.3. Remove crankshaft thrust bearings (3) from the rear main bearing. Install the main bearings dry when the clearance checks are made. Put clean engine oil on the main bearings for final assembly.
Make sure the upper and lower halves of the main bearings are installed so the bearing tabs fit into the notch in the cylinder block and the main bearing caps.
4. Clean the surfaces in the cylinder block for the main bearings. Use tool (A), and install new upper halves of main bearings (bearings with the oil hole) (2) in the cylinder block. Do not put oil on the bearing.5. Clean the surfaces of the main bearing caps for the main bearings. Install the new lower halves of main bearings (2) in the main caps without oil. The serviceman must be very careful to use Plastigage, tool (B) correctly. The following points must be remembered:...Make sure that the backs of the bearings and the bores are clean and dry....Make sure that the bearing locking tabs are properly seated in their slots....The crankshaft must be free of oil where the Plastigage touches it....If the main bearing clearances are checked with the engine upright or on its side, the crankshaft must be supported. Use a jack under an adjacent crankshaft counterweight and hold the crankshaft against the crown of the bearing. If the crankshaft is not supported, the weight of the crankshaft will cause incorrect readings....Do not allow the Plastigage to extend over the edge of the bearing....Install the bearing cap using the correct torque-turn specifications. Do not use an impact wrench. Be careful not to dislodge the bearing when the cap is installed....Do not turn the crankshaft with the Plastigage installed....Carefully remove the cap but do not remove the Plastigage. Measure the width of the Plastigage while it is in the bearing cap or on the crankshaft journal. Do this by using the correct scale on the package. Record the measurements....Remove the Plastigage (B) before reinstalling the cap.When using Plastigage, the readings can sometimes be unclear. For example, all parts of the Plastigage are not the same width. Measure the major widths to make sure that they are within the specification range. Also, experience has shown that when checking clearances tighter than 0.10 mm (.004") the readings may be low by 0.013 to 0.025 mm (.0005 to .0010"). Out-of-round journals can give faulty readings. Also, journal taper may be indicated when one end of the Plastigage is wider that the other.For complete details concerning measuring bearing clearances, see Engine Bearings And Crankshafts, Form No. SEBD0531.6. Check the main bearing clearance with Plastigage (B) as follows:a. Put a piece of Plastigage (B) on the crown of the bearing half that is in the cap or on the crankshaft journal as shown.
Make sure the part number on the main bearing caps is toward the front of the engine and the number on the main bearing caps is the same as the number on the outside (camshaft side) of the cylinder block.
b. Put main bearing caps (1) in position on the cylinder block. Put 2P2506 Thread Lubricant on the bolt threads and the contact surface of the bolts heads, and install the bolts. Tighten the bolts to a torque of 40 4 N m (30 3 lb ft).c. Put a mark on each bolt and main bearing cap; then turn the bolts an extra 90° from the mark.d. Remove the main bearing caps, and measure the width of Plastigage (B) to find the bearing clearance. The main bearing clearance for new bearings must be 0.076 to 0.165 mm (.0030 to .0065 in). The maximum permissible clearance with used main bearings must not be more than 0.25 mm (.010 in). 7. Put clean oil on the thrust bearings, and install new thrust bearings for the rear main bearing. Install the thrust bearings with the identification "BLOCK SIDE" toward the bearing saddle and the side with the oil grooves toward the crankshaft. Also, put the tabs on the thrust bearings in the machined area in the cylinder block. Tabs (4) on thrust bearings (3) will not let the thrust bearings be installed backward. 8. Install main bearing caps (1), and tighten the bolts as in Steps 6b and 6c.9. Remove the remainder of the main bearing caps, and do Steps 2, 4, 5, 6 and 8.End By:a. install oil pumpb. install oil pan plate