Piston Installation - Mercury 225 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. (12.7 mm) 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
0.010 in. to 0.018 in. (0.25 mm to 0.46 mm). 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.
IMPORTANT: 3 Liter Work/225 EFI/250 EFI engines have top and bottom indicated pis-
ton rings and should be installed accordingly. The top ring is marked T1 and the bot-
tom ring is marked T2. The "T" represents the top side of of the ring. The bottom ring
is stepped to trap oil and bring it into the cylinder bores on the upward stroke.
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.
90-884294 OCTOBER 2001
a a
c
d
a - Piston Ring
b - Dots (Faces Up)
c - Feeler Gauge
d - Ring End Gap
c
a - T1 top ring
b - T2 bottom ring
c - Step
b
a
b
POWERHEAD
e
f
52317
e - Dot or Letter
f - Piston Ring
58126
Page 4A-63