Check Valves; Piston And Piston Rings - Mercury 75 Service Manual

Check Valves

REMOVAL
Remove carburetors and intake manifold/reed
block assemblies.
Grasp carrier and remove carrier/check valve as-
sembly from crankcase cover.
a
a - Carrier/Check Valve Assembly
Push check valve out of carrier. If nylon ball within
check valve is stuck or carrier is charred, replace
check valve and/or carrier as required.
IMPORTANT: SINGLE HOLE side of check valve
MUST FACE CRANKCASE.
c
a
b
a - Check Valve
b - Carrier
c - Single Hole
d - Double Hole
4-42 - POWERHEAD
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d
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INSTALLATION
Install check valve (if removed) inside of carrier
(single hole of valve faces tapered end of carrier).
Align carrier tab with slot in crankcase cover and
insert check valve/carrier assembly into cover.
b
a
a - Check Valve/Carrier Assembly
b - Slot
c - Crankcase Cover
Clean mating surfaces of crankcase cover and
intake manifold. Install new gaskets.
Install intake manifold/reed block assemblies to
crankcase cover. Refer to PAGE 4-58 for torque
specification and tightening sequence.
Install carburetors. Torque carburetor (AIR BOX)
stud nuts to 100 lb. in. (11.3 N
m).
Carburetors MUST BE SYNCHRONIZED. Refer
to SECTION 2C for proper procedures.
Reinstall air box cover.
Reinstall top cowling.

Piston and Piston Rings

IMPORTANT: If engine was submerged while en-
gine was running, piston pin and connecting rod
may be bent. If piston pin is bent, piston must be
replaced. Piston pins are not sold separately be-
cause of matched fit into piston. If piston pin is
bent, connecting rod must be checked for
straightness (refer to "Connecting Rods" for
checking straightness).
Inspect piston for scoring and excessive piston
skirt wear.
90-830234R3 DECEMBER 1997
c
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