811590 Mercruiser ROCKER ARM

Illustration 1 g01611477This piston has a Keystone top and Keystone intermediate rings. The 1U-6431 Piston Ring Groove Gauge is necessary for measuring the ring grooves in Keystone pistons. For correct use of the gauge group, see the instruction card that is with the gauge group.Top Piston Ring (1)
Install the top ring with the "Up-1" side toward the top of the piston.Thickness of new top piston ring ... 3.91 mm (0.154 inch)When the piston ring is installed in a cylinder liner with a bore size of 170 mm (6.7 inch), the clearance between the ends of the piston ring is the following value. ... 0.625 0.125 mm (0.0246 0.0049 inch)The increase in the clearance between the ends of the piston ring for each 0.03 mm (0.001 inch) increase in the cylinder liner bore size is the following value. ... 0.08 mm (0.003 inch)Intermediate Piston Ring (2)
Install the intermediate ring with the "Up-2" side toward the top of the piston.Thickness of new intermediate piston ring ... 3.785 mm (0.1490 inch)When the piston is installed in a cylinder liner with a bore size of 170 mm (6.7 inch), the clearance between the ends of the piston ring is the following value. ... 1.00 0.15 mm (0.039 0.006 inch)The increase in the clearance between the ends of the piston ring for each 0.03 mm (0.001 inch) increase in the cylinder liner bore size is the following value. ... 0.08 mm (0.003 inch)Oil Control Piston Ring (3)
Width of groove in piston for the new piston ring ... 5.050 0.010 mm (0.1988 0.0004 inch)Thickness of new piston ring ... 4.954 0.019 mm (0.1950 0.0007 inch)Clearance between groove and new piston ring ... 0.067 to 0.125 mm (0.0026 to 0.0049 inch)When the piston ring is installed in a cylinder liner with a bore size of 170 mm (6.7 inch), the clearance between the ends of the piston ring is the following value. ... 0.70 0.19 mm (0.028 0.007 inch)The increase in the clearance between the ends of the piston ring for each 0.03 mm (0.001 inch) increase in the cylinder liner bore size is the following value. ... 0.08 mm (0.003 inch)Install the oil control ring so that the gap in the spring is 180 degrees away from the gap in the ring. The white portion of the spring must be visible at the ring gap.After all of the piston rings have been installed, rotate the rings so that the end gaps are separated by 120 degrees. The ring gap for the oil ring must be aligned in the plane of the pin bore.Piston Pin Bore (4)
Measure the piston pin bore in the bushings in two places for each bushing in a vertical direction.Bore diameter in the crown assembly for piston pin ... 70.035 0.005 mm (2.7573 0.0002 inch)Bore diameter in the piston skirts for piston pin ... 69.983 0.005 mm (2.7552 0.0002 inch)Piston Pin (5)
Measure the piston pin diameter on each end in a vertical and horizontal direction.Inside diameter of the piston pin ... 35.0 0.5 mm (1.38 0.02 inch)Outside diameter of the piston pin ... 69.962 0.005 mm (2.7544 0.0002 inch)Length of the piston pin ... 133.00 0.13 mm (5.236 0.005 inch)Pin Retainer (6)
Assemble the retainer with the opening toward the top of the piston.