Mercury 40

SPECIFICATIONS
90-828631R3 MARCH 1999 Page 1A-3
CARBURETOR
Idle rpm (Out Of Gear)
45 hp
40/50 hp
Idle rpm (In Forward Gear)
45 hp
40/50 hp
Wide Open Throttle rpm (WOT)
Range
Main Jet Size
40/45 hp
Carburetors 1 and 2
Carburetors 3 and 4
50 hp
Pilot Jet
Float Height
950 ± 25 rpm
825 ± 25 rpm
850 ± 25 rpm
725 ± 25 rpm
5500–6000 rpm
#104
#103
#112
#42
0.39 ± 0.02 in. (10.0 ± 0.5 mm)
CYLINDER BLOCK
Type
Displacement
Number of Cylinders
4 Stroke Cycle – Over Head Camshaft
57 cu. in. (935cc)
4
STROKE Length 2.953 in. (75 mm)
CYLINDER BORE
Diameter
Standard
Oversize-0.020 in. (0.050 mm)
Taper/Out of Round Maximum
Bore Type
2.4803 in. (63.0 mm)
2.5003 in. (63.5 mm)
0.003 in. (0.08 mm)
Steel
PISTON
Piston Type
O.D. at Skirt
Standard
Oversize-0.020 in. (0.50mm)
Aluminum
2.4783-2.4789 in. (62.950-62.965 mm)
2.4983-2.4989 in. (63.450-63.465 mm)
PISTON
CLEARANCE
Piston to Cylinder Clearance 0.0014 - .0026 in. (0.035 - 0.065 mm)
RINGS
Ring End Gap (Installed)
Top
Middle
Bottom (Oil Ring)
Side Clearance:
Top
Middle
0.006 - 0.012 in. (0.15 - 0.30 mm)
0.012 - 0.020 in. (0.30 - 0.50 mm)
0.008 - 0.028 in. (0.20 - 0.70 mm)
0.002 - 0.003 in. (0.04 - 0.08 mm)
0.001 - 0.003 in. (0.03 - 0.08 mm)
COMPRESSION
RATIO
Compression Ratio
Cylinder Compression (cold engine
@ W.O.T.)
9.8:1
170 -190 lb/in
2
(Peak)
PISTON PIN Piston Pin Diameter 0.6285-0.6287 in. (15.965 - 15.970 mm)
CONNECTING
ROD
Oil Clearance (Big End)
Small End Inside Diameter
0.0008 - 0.0020 in. (0.020 - 0.052 mm)
0.6293 - 0.6298 in. (15.985-15.998 mm)