811545 Mercruiser SEAL

Illustration 1 g00295711
Piston and rings
Note: The word "Front" or an arrow which is marked on the piston crown must be toward the front of the engine. If the piston crown is not marked, put the narrowest side of the piston crater toward the side of the engine with the fuel injection pump. The shortest distance between the edge of the piston crater and the edge of the piston is the narrowest side of the piston crater.Note: Be sure that the ring end gaps of all the piston rings have 120 degrees spacing from each other.Note: Refer to Systems Operation, "General Information" for the location of the serial number.Naturally Aspirated Engines
(1) Width of groove in piston for top ring ... 2.57 to 2.59 mm (.101 to .102 inch)Thickness of top ring ... 2.48 to 2.49 mm (.097 to .098 inch)Clearance between groove and piston ring ... 0.08 to 0.11 mm (.003 to .004 inch)Clearance between the ends of the top ring with a cylinder liner without any wear ... 0.40 to 0.85 mm (.016 to .033 inch) (2) Width of groove in piston for intermediate ring ... 2.55 to 2.57 mm (.100 to .101 inch)Thickness of intermediate ring ... 2.48 to 2.49 mm (.097 to .098 inch)Clearance between groove and intermediate ring ... 0.06 to 0.09 mm (.002 to .003 inch)Clearance between the ends of the intermediate ring with a cylinder liner without any wear ... 0.30 to 0.76 mm (.012 to .030 inch) (3) Width of groove in piston for oil control ring ... 4.030 to 4.060 mm (.1587 to .1598 inch)Thickness of oil control ring ... 3.980 to 3.990 mm (.1566 to .1571 inch)Clearance between groove and oil control ring ... 0.04 to 0.08 mm (.002 to .003 inch)Clearance between the ends of oil control ring with a cylinder liner without any wear ... 0.38 to 0.84 mm (.015 to .033 inch) (4) Diameter of new piston pin ... 34.920 to 34.925 mm (1.3748 to 1.3750 inch)Bore for piston pin ... 34.928 to 34.934 mm (1.3751 to 1.3754 inch)Turbocharged Engines
(1) Shape of groove in piston for top ring ... TaperShape of top ring ... TaperClearance between the ends of top ring in a cylinder liner without any wear ... 0.35 to 0.75 mm (.014 to .030 inch) (2) Width of groove in piston for intermediate ring ... 2.56 to 2.58 mm (.101 to .102 inch)Thickness of intermediate ring ... 2.48 to 2.49 mm (.097 to .098 inch)Clearance between groove and intermediate ring ... 0.07 to 0.11 mm (.003 to .004 inch)Clearance between the ends of an intermediate ring in a cylinder liner without any wear ... 0.30 to 0.76 mm (.012 to .030 inch) (3) Width of groove in piston for oil control ring ... 4.040 to 4.060 mm (.1591 to .1598 inch)Thickness of oil control ring ... 3.98 to 3.99 mm (.156 to .157 inch)Clearance between groove and oil control ring ... 0.05 to 0.08 mm (.002 to .003 inch)Clearance between the ends of an oil control ring in a cylinder liner without any wear ... 0.38 to 0.84 mm (.015 to .033 inch) (4) Diameter of new piston pin ... 38.095 to 38.100 mm (1.4998 to 1.5000 inch)Bore for piston pin ... 38.103 to 38.109 mm (1.5000 to 1.5004 inch)Piston Height
Illustration 2 g00891532
Quadram piston
There are two different designs for the crown of the piston. One design is the Quadram piston. There is only one grade of piston for the replacement of a Quadram piston.Grade of piston for service ... LHeight of a Quadram piston above the top face of the cylinder block ... 0.14 to 0.36 mm (0.005 to 0.014 inch)
Illustration 3 g00891548
Fastram piston
The other style of piston is the Fastram piston. The piston height above the top face of the cylinder block is controlled by different grades of height of the piston. Identification of the height grade is by the letter that is stamped on the top of each piston. The height grade can be checked by measuring from the center of the piston pin to the top of the piston. The difference between each grade of height is 0.045 mm (0.0018 inch). Table 1 provides the specifications for the grade of height for a Fastram piston.
Table 1
Height Grades for the Piston
Letter on top of Piston Height Dimension Latest Equivalent Grade
A(1) 70.334 mm (2.7690 inch) G
B(1) 70.289 mm (2.7673 inch) H
C(1) 70.244 mm (2.7655 inch) J
D(1) 70.199 mm (2.7637 inch) K
E(1) 70.154 mm (2.7620 inch) L
F 70.391 mm (2.7713 inch) -
G 70.345 mm (2.7695 inch) -
H 70.299 mm (2.7677 inch) -
J 70.253 mm (2.7659 inch) -
K 70.207 mm (2.7640 inch) -
L 70.161 mm (2.7622 inch) -
(1) Earlier enginesHeight of a Fastram piston above the top face of the cylinder block ... 0.38 to 0.50 mm (0.015 to 0.020 inch)