816670 Mercruiser NUT, (.500-20)

2. Turn the crankshaft until two pistons are at bottom center. Remove connecting rod caps (1) from the two connecting rods.3. Put tape or pieces of rubber hose over the threads of the connecting rod bolts. This will prevent damage to the crankshaft during removal of the pistons.
Do not let the connecting rods hit the bottom edge of the cylinder liners or the crankshaft during removal and installation of the pistons.
TYPICAL EXAMPLE4. Push the piston and connecting rod away from the crankshaft until the piston rings are above the cylinder liner. Remove the two pistons (2) and the connecting rods from the engine.5. Keep each connecting rod cap with its respective connecting rod and piston. Put identification on each connecting rod as to its location in the engine for use at assembly of the engine.6. Do Steps 2 through 5 for the remainder of the pistons.Install Pistons
1. Turn the crankshaft until the bearing journals for the pistons to be installed are at bottom center.2. Put clean engine oil on the crankshaft journals and on the inside of the cylinder liners. Put clean engine oil on the piston rings and connecting rod bearings.3. Move the rings on the piston until the ring openings are approximately 90° apart.
Never install the ring compressor on the piston unless the cylinder liner is used as a guide. Damage to the piston rings can be the result.
TYPICAL EXAMPLE4. Put ring compressor (A) in position on the cylinder liner. Put the connecting rod and piston in position in the same cylinder liner from which it was removed and into the ring compressor. Make sure the "V" mark on the piston is in alignment with the "V" mark on the cylinder block.5. Push the piston into place as the connecting rod is put into position on the crankshaft. 6. Put clean engine oil on bearings, bolt threads and surfaces of the nuts that make contact with the connecting rod caps. Put caps (1) in position on the connecting rods and install the nuts. Tighten the nuts to a torque of 30 3 lb.ft. (40 4 N m). Put a mark on each nut and the end of each bolt. Tighten the nuts 90° more.
When connecting rod caps are installed, make sure the number on the side of the cap is next to and respective with the number on the side of the connecting rod.
7. Follow the same above procedure for installation of the remainder of the pistons.end by:a) install oil pan plateb) install cylinder headDisassemble And Assemble Pistons
start by:a) remove pistons 1. Remove rings from the piston with tool (A). 2. Remove retainer ring (3), piston pin (1) and connecting rod (2) from the piston.3. Clean the piston ring grooves on the old pistons with an acceptable ring groove tool. For clearances on pistons and rings, see PISTONS AND RINGS in SPECIFICATIONS.4. See SPECIAL INSTRUCTION, Form SMHS7295 for USE OF PISTON REMOVAL AND INSTALLATION TOOLS. Be sure to remove the bearings from the crankshaft end of the connecting rod.5. Heat the connecting rod in an oven to a temperature of 350° - 500°F (176° - 260°C). Never use a direct flame to heat a connecting rod. 6. Put the connecting rod in position on tooling (B). Put a new rod pin bearing in position. Make sure the rod pin bearing joint (4) is 90° from a center line through crankshaft and pin bearing bores. 7. Use tooling (B) to remove the old rod pin bearing and install the new rod pin bearing with one operation.8. Use a pin boring machine to make the bearing the correct size. The bore in the bearing (new) must be 1.5017 .0003 in. (38.143 0.008 mm). The maximum permissible clearance between the bearing and piston pin (worn) must not be more than .003 in. (0.08 mm).9. Put the connecting rod in position in the piston with the bearing tab groove and number identification on the same side as the "V" mark on top of the piston. 10. Install piston pin (1) and retaining ring (3).11. Check the clearance between the ends of the piston rings (end gap) with the rings installed in a cylinder liner with a bore size of 4.750 in. (120.65 mm). The clearance of the top ring is .020 .003 in. (0.51 0.08 mm) and the clearance for the oil ring is .018 .005 in. (0.46 0.13 mm).12. Install the oil ring spring in the oil ring groove of the piston. The oil ring (7) must be installed on the piston with the ring end gap 180° from the oil ring spring joint. 13. Install the oil ring (7) on the piston with tool (A).14. The two compression rings have marks "UP-1" and "UP-2". The rings must be installed with these marks toward the top of the piston with "UP-1" as the top ring. After installation of all three piston rings, put piston rings in position so gaps in rings are 120° apart.15. Check the clearance between the piston ring grooves and the rings. The maximum permissible clearance between all of the rings and piston grooves must not be more than .006 in. (0.15 mm). The clearance between the top ring (new) and groove must be .0028 to .0046 in. (0.071 to 0.117 mm). The clearance between the oil ring (new) and groove must be .0015 to .0035 in. (0.038 to 0.089 mm). Make sure the top piston ring and oil ring end gaps are 180° apart before the pistons are installed.end by:a) install pistons