Mercury 200 OptiMax Jet Drive, Service Manual, Page: 306 / 391

Powerhead
90-8M0050731 MAY 2011 Page 4A-41
2. A tool can be made for cleaning the inner diameter of the tapered ring grooves. The tool can be made from a broken tapered
piston ring with the side taper removed to enable the inside edge of the ring to reach the inner diameter of the groove. Carefully
scrape carbon from the inner diameter of the ring grooves. Care must be taken not to damage the grooves by scratching the
side surfaces of the grooves.
a - Ring grooves
Measuring Piston
The piston has a barrel profile shape and is not a true diameter.
Measure the piston at a point 24 mm (0.945 in.) from the bottom of the piston skirt, 90° to the wrist pin opening.
a - 24 mm (0.945 in.)
b - Piston diameter
Piston diameter
Standard
88.7095 ± 0.0127 mm (3.4925 ± 0.0005 in.)
Oversize 89.0905 ± 0.0127 mm (3.5075 ± 0.0005 in.)
Cylinder Heads and Exhaust Divider Plate
1. Inspect the internal surface of the cylinder heads for possible damage as a result of piston or foreign material striking the
cylinder heads.
IMPORTANT: Cylinder head warpage must not exceed 0.025 mm (0.001 in.) over the entire length of the cylinder head. If
the warpage exceeds 0.025 mm (0.001 in.) in the narrow portion of the cylinder head, the cylinder head must be replaced.
The cylinder head must not be resurfaced, as the O‑ring groove depth in the head will be reduced, which will result in cylinder
leakage.
2. Replace the cylinder head as necessary.
3. Thoroughly clean the gasket surfaces of the exhaust divider plate.
4. Inspect the exhaust divider plate for deep grooves, cracks, or distortion that may cause leakage. Replace the part as
necessary.
Crankshaft
1. Inspect the splines on the crankshaft end of the driveshaft for wear. Replace the crankshaft if necessary.
2. Check the crankshaft for runout. Maximum runout is 0.152 mm (0.006 in.). Replace the crankshaft if necessary.
3. Inspect the crankshaft oil seal surfaces. The sealing surfaces must not be grooved, pitted, or scratched. Replace the crankshaft
if necessary.
4. Check all crankshaft bearing surfaces for rust, water marks, chatter marks, uneven wear, or overheating.
a
8652
b
a
33506