Piston Installation - Mercury 150 EFI Service Manual

Piston Installation

1. Before installing new piston rings, check gap between ring ends by placing each ring
in its respective cylinder, then pushing ring about 1/2 in. (12.7mm) into cylinder using
piston to assure proper position.
2. Check end gap of each new piston ring with a feeler gauge. End gap must be within
0.018 in. to 0.025 in. (0.45mm to 0.64mm). If end gap is greater, check other piston rings
in cylinder bore, until rings (within tolerance) are found.
IMPORTANT: Piston ring side with dot or letter must be facing up.
3. Use Piston Ring Expander (91-24697) and install piston rings (dot side up) on each pis-
ton. Spread rings just enough to slip over piston.
4. Check piston rings to be sure that they fit freely in ring groove.
90-883728 JULY 2001
a
a - Piston Ring
b - Dots (Faces Up)
c - Feeler Gauge
d - Ring End Gap
Dot or Letter
b
c
d
Piston Ring
POWERHEAD
51852
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