🔎 Mercury 40, 4 (GNAT 2 CYL.) Reference Library — Exploded parts diagrams (14 diagrams), specifications, common issues, and maintenance checklist.
The Mercury 40, 4 (GNAT 2 CYL.) is a 4-Stroke, Inline 4-Cylinder, EFI, SOHC outboard motor. Commonly used on jon boats, pontoons, and mid-size utility craft.
Quick Reference Specifications
| Specification |
Value |
| Engine Type |
4-Stroke, Inline 4-Cylinder, EFI, SOHC |
| Horsepower |
40 HP |
| Displacement |
995 cc |
| Bore x Stroke |
65 mm x 75 mm |
| Spark Plug (Type & Gap) |
NGK IZFR6F-11 |
| Engine Oil Capacity |
3.0 L (3.17 quart) |
| Recommended Engine Oil |
SAE 25W-40 Mercury FourStroke Oil |
| Gear Case Oil Capacity |
440 mL (14.9 fl oz) |
| Idle Speed (in gear) |
700 ± 50 RPM (in gear) |
| Full Throttle RPM Range |
5500-6000 |
| Fuel |
Unleaded Gasoline, 87 Octane min. |
Always verify specifications against your owner's manual for your specific serial number range.
Common Issues & Recommended Parts
Below are common maintenance scenarios for the Mercury 40, 4 (GNAT 2 CYL.):
-
Water Pump / Overheating: If the tell-tale stream is weak or absent, the water pump impeller likely needs replacement. Inspect annually or every 100 hours. → Recommended: Water Pump Impeller Kit
-
Engine Oil / Maintenance Light: 4-stroke engines require regular oil and filter changes. Use marine-grade oil rated for your engine. Change every 100 hours or annually. → Recommended: Oil Filter, Engine Oil
-
Fuel Injector Issues (EFI models): Rough idle or misfires may indicate clogged fuel injectors. Use fuel stabilizer and clean injectors periodically. → Recommended: Fuel Injector, Fuel Filter
-
Gear Case Oil Leak: Check lower unit seals if gear oil appears milky (water contamination). Replace seals and gaskets during lower unit service. → Recommended: Lower Unit Seal Kit, Drain Plug Gaskets
-
Anode Corrosion: Inspect sacrificial anodes regularly, especially in saltwater. Replace when 50% depleted to protect against galvanic corrosion. → Recommended: Zinc/Aluminum Anode Kit
Parts Diagrams & OEM Part Numbers
Expand the sections below to view detailed exploded parts diagrams and find the exact OEM replacement components for your Mercury 40, 4 (GNAT 2 CYL.).
▶BOTTOM COWL (32 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
2154-7603 |
BOTTOM COWL (SERIAL #9141799 AND UP) |
| 2 |
714933 |
MOLDING, BOTTOM COWL (2" - 6-1/2" - 15") |
| 3 |
70455 |
COVER, BOTTOM COWL |
| 4 |
10-69079 |
SCREW, COVER TO BOTTOM COWL (7/16") |
| 5 |
86055T |
HANDLE, SHIFT SERIAL Comment: #9210546 AND UP |
| 6 |
86056A1 |
SHAFT, SHIFT Comment: #9210546 AND UP |
| 7 |
10-69560 |
SCREW, SHIFT HANDLE TO SHAFT (1 1/4") Comment: #9210546 AND UP |
| 8 |
13-26996 |
LOCKWASHER, SHIFT HANDLE SCREW Comment: #9210546 AND UP |
| 9 |
66414 |
CAM, SHIFT DETENT |
| 10 |
17-25905 |
ROLL PIN, CAM TO SHIFT SHAFT |
| 11 |
23-26856 |
BUSHING, SHIFT SHAFT |
| 12 |
25-16524 |
"O" RING, SHIFT SHAFT |
| 13 |
72733 |
ARM, SHIFT |
| 14 |
10-72734 |
SET SCREW, SHIFT ARM (5/16") |
| 15 |
18-210711 |
COTTER PIN, SHIFT SHAFT |
| 16 |
24-39627 |
SPRING, DETENT |
| 17 |
39601 |
PLATE, DETENT SPRING |
| 18 |
10-25764 |
SCREW, DETENT SPRING TO BOTTOM COWL (1/2") |
| 19 |
27-92874 |
GASKET, DRIVE SHAFT HOUSING/BOTTOM COWL |
| 20 |
69602 |
TRIM COVER Comment: SERIAL #9141798 AND BELOW |
| 21 |
10-75827 |
SCREW, TRIM COVER TO BOTTOM COWL Comment: SERIAL #9141798 AND BELOW |
| 22 |
53-72168 |
"E" RING, RETAINER |
| 23 |
70393 |
RETAINER, STARTER HANDLE Comment: (SERIAL #9190380 AND UP) |
| 24 |
19-74258 |
PLUG, BOTTOM COWL - FUEL ADAPTOR |
| 25 |
70462 |
ARM, LATCH CRANK |
| 26 |
24-70459 |
SPRING, LATCH CRANK |
| 27 |
75263 |
CRANK, FRONT LATCH |
| 28 |
13-34632 |
WAVE WASHER, LATCH HANDLE |
| 29 |
92798 |
HANDLE, LATCH BOTTOM COWL |
| 30 |
17-38489 |
ROLL PIN, LATCH HANDLE TO CRANK |
| 31 |
74802 |
STOP, SHIFT ARM |
▶CARBURETOR ASSEMBLY (16 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
89977A2 |
CARBURETOR ASSEMBLY |
| 2 |
1395-6043 |
RETAINER, JET (.041) |
| 4 |
1395-8155 |
FUEL BOWL |
| 6 |
1395-5898 |
FLOAT |
| 7 |
1395-5904 |
SPRING, FLOAT |
| 9 |
1395-4805 |
SCREEN, FILTER |
| 10 |
1395-5900 |
NOZZLE |
| 14 |
1395-5896 |
SHAFT, CHOKE |
| 15 |
1395-5905 |
SPRING, CHOKE RETURN |
| 16 |
1395-5897 |
VALVE, CHOKE |
| 17 |
1395-5902 |
SCREW, VALVE |
| 18 |
1395-5894 |
SHAFT, THROTTLE |
| 19 |
1395-5903 |
SPRING, THROTTLE RETURN |
| 20 |
1395-8670 |
VALVE, THROTTLE |
| 22 |
1395-6103 |
SPRING, IDLE NEEDLE |
| 23 |
1395-6618 |
REPAIR PARTS KIT |
▶CLAMP AND SWIVEL BRACKET ASSEMBLY (31 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
1479-7291A1 |
CLAMP BRACKET ASSEMBLY (PORT) Comment: WASHER ATTACHED WITH A SCREW |
| 2 |
1478-7289A1 |
CLAMP BRACKET ASSEMBLY (STARBOARD) Comment: WASHER ATTACHED WITH A SCREW |
| 3 |
10-77190A4 |
THUMB SCREW ASSEMBLY Comment: WASHER ATTACHED WITH A SCREW |
| 4 |
78971 |
HANDLE, THUMB SCREW Comment: WASHER ATTACHED WITH A SCREW |
| 5 |
17-78970 |
GROOVE PIN, THUMB SCREW Comment: WASHER ATTACHED WITH A SCREW |
| 6 |
12-73719 |
WASHER, THUMB SCREW Comment: WASHER ATTACHED WITH A SCREW |
| 6A |
10-768042 |
SCREW, THUMB SCREW WASHER Comment: WASHER ATTACHED WITH A SCREW |
| 7 |
10-96917 |
SCREW, CLAMP BRACKET Comment: (SERIAL #9213206 AND UP) |
| 8 |
12-68920 |
WASHER, CLAMP BRACKET STUD OR SCREW |
| 9 |
11-8M0204726 |
NUT, CLAMP BRACKET STUD OR SCREW |
| 10 |
16-68925 |
STUD, CLAMP BRACKET |
| 11 |
13-26992 |
LOCKWASHER< CLAMP BRACKET STUD |
| 12 |
11-29598 |
NUT, CLAMP BRACKET STUD |
| 13 |
17-68929A2 |
TILT PIN ASSEMBLY |
| 14 |
71369 |
COVER, EXHAUST RELIEF Comment: USED ON EARLY MODELS ONLY |
| 15 |
10-48408 |
SCREW, EXHAUST RELIEF COVER (1/2") Comment: USED ON EARLY MODELS ONLY |
| 16 |
1477-7400A2 |
SWIVEL BRACKET ASSEMBLY |
| 17 |
10-69067 |
SCREW, SWIVEL BRACKET (1 3/8") |
| 17A |
22-8M0169589 |
GREASE FITTING, SWIVEL BRACKET |
| 17B |
19-77633Q |
LUBRICAP, GREASE FITTING |
| 18 |
10-71105A1 |
THUMB SCREW ASSEMBLY |
| 19 |
76110A1 |
TILT LEVER ASSEMBLY Comment: (SERIAL #9141799 AND UP) |
| 20 |
24-68932 |
SPRING, TORSION - PORT |
| 21 |
68968 |
ROD, REVERSE LOCK |
| 22 |
18-25191 |
COTTER PIN, REVERSE LOCK ROD |
| 23 |
68972 |
LEVER, REVERSE LOCK |
| 24 |
24-73124 |
SPRING, TORSION - STARBOARD |
| 25 |
22-8M0169589 |
GREASE FITTING (NOT USED WITH REF. #14) |
| 25A |
19-77633Q |
LUBRICAP, GREASE FITTING |
| 26 |
24-62143 |
SPRING, TILT PIN |
| 27 |
23-75065 |
SPACER, REVERSE LOCK ROD |
▶CRANKSHAFT, PISTON AND CONNECTING ROD (21 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
458-5549 |
CRANKSHAFT |
| 2 |
626-5547A5 |
CONNECTING ROD ASSEMBLY |
| 3 |
10-72455 |
SCREW, CONNECTING ROD |
| 4 |
14-72454 |
TAB WASHER, CONNECTING ROD SCREW |
| 5 |
29-68944 |
NEEDLE BEARING, CONNECTING ROD |
| 6 |
68953A1 |
LINER ASSEMBLY, CONNECTING ROD - CRANKPIN |
| 8 |
31-68949 |
ROLLER BEARING, CONNECTING ROD - PISTON PIN |
| 9 |
758-8076A2 |
PISTON ASSEMBLY |
| 10 |
40-68950 |
LOCK RING, PISTON |
| 11 |
39-70175A12 |
PISTON RING ASSEMBLY |
| 12 |
26-30530 |
OIL SEAL, CRANKSHAFT - UPPER |
| 13 |
31-78099 |
ROLLER BEARING, CRANKSHAFT - UPPER |
| 14 |
71841 |
RING, CRANKSHAFT |
| 15 |
30-69389 |
BALL BEARING, CRANKSHAFT - LOWER |
| 16 |
53-68952 |
RETAINING RING, BALL BEARING - LARGE |
| 17 |
53-27275 |
RETAINING RING, BALL BEARING - SMALL |
| 18 |
26-77494 |
OIL SEAL, CRANKSHAFT |
| 19 |
25-62706 |
"O" RING, CRANKSHAFT |
| 20 |
70786A1 |
COUPLING ASSEMBLY, CRANKSHAFT |
| 21 |
26-76266 |
SEAL, COUPLING |
▶CYLINDER BLOCK AND CRANKCASE ASSEMBLY (33 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
862-7713A2 |
BLOCK AND CRANKCASE ASS'Y Comment: SERIAL #9210546 AND UP |
| 2 |
16-728091 |
STUD, POWERHEAD (1 5/8") Comment: SERIAL #9210546 AND UP |
| 3 |
17-8M0084726 |
PIN, CYLINDER BLOCK |
| 5 |
16-20353 |
STUD, REED BLOCK AND CARBURETOR |
| 6 |
22-56800 |
PLUG, PIPE - CYLINDER BLOCK |
| 7 |
10-70732 |
SCREW, CRANKCASE TO CYLINDER BLOCK (2") |
| 8 |
10-28635 |
SCREW, CRANKCASE TO CYLINDER BLOCK (5/8") |
| 9 |
10-28667 |
SCREW, CRANKCASE TO CYLINDER BLOCK (1") |
| 10 |
68953A1 |
LINER ASSEMBLY, CYLINDER BLOCK |
| 12 |
29-71840 |
NEEDLE BEARING, CENTER MAIN |
| 13 |
77585 |
COVER, EXHAUST MANIFOLD Comment: SERIAL #9210546 AND UP |
| 14 |
27-77586 |
GASKET, EXHAUST MANIFOLD COVER Comment: SERIAL #9210546 AND UP |
| 15 |
10-32228 |
SCREW, EXHAUST MANIFOLD COVER (5/8") Comment: SERIAL #9210546 AND UP |
| 16 |
1027-5546 |
COVER, CYLINDER BLOCK |
| 17 |
27-68942 |
GASKET, CYLINDER BLOCK COVER |
| 18 |
10-32228 |
SCREW, CYLINDER BLOCK COVER (5/8") |
| 19 |
27-68941 |
GASKET, BLOCK TO BOTTOM COWL |
| 20 |
11-8M0207775 |
NUT, POWERHEAD STUDS |
| 22 |
32-9938779 |
HOSE, BLEED |
| 23 |
22-56759 |
FITTING ADAPTOR |
| 24 |
21-64871A2 |
CHECK VALVE ASSEMBLY, CRANKCASE |
| 25 |
69498 |
REED BLOCK |
| 26 |
27-70415 |
GASKET, CRANKCASE TO REED BLOCK |
| 27 |
34-69499A1 |
REED ASSEMBLY |
| 28 |
34-69500 |
REED STOP |
| 29 |
10-28430 |
SCREW, REED AND REED STOP (1/4") |
| 30 |
27-70416 |
GASKET, REED BLOCK TO ADAPTOR |
| 31 |
70420 |
ADAPTOR, CARBURETOR TO REED BLOCK |
| 32 |
79746 |
BRACKET, CABLE MOUNTING Comment: (SERIAL #9210596 AND UP) |
| 33 |
10-69022 |
SCREW, BRACKET TO ADAPTOR (1/2") |
| 34 |
10-20055 |
SCREW, CABLE MOUNTING BRACKET (7/16") |
| 35 |
74777 |
FILLER BLOCK, REED BLOCK TO CRANKCASE Comment: (EARLY MODELS) |
▶DRIVE SHAFT HOUSING ASSEMBLY (13 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
1580-6673A2 |
DRIVE SHAFT HOUSING ASSEMBLY Comment: SERIAL #9210596 AND UP |
| 2 |
16-75321 |
STUD, DRIVE SHAFT HOUSING (LONG SHAFT) |
| 3 |
10-79953Q04 |
SCREW, GREASE FILLER |
| 4 |
12-191833 |
WASHER, GREASE FILLER SCREW |
| 5 |
32-75308 |
WATER TUBE (LONG SHAFT) |
| 6 |
26-36556 |
SEAL, WATER TUBE |
| 7 |
23-13127 |
WASHER, WATER TUBE SEAL |
| 8 |
68976 |
CLAMP, CO-PILOT |
| 9 |
88669 |
MOUNT Comment: RUBBER - DRIVE SHAFT HOUSING (BOTTOM) |
| 10 |
23-74308 |
BUSHING, RUBBER MOUNT |
| 11 |
98496A1 |
BRACKET ASSEMBLY, STEERING ARM |
| 12 |
10-68918 |
SCREW, STEERING ARM BRACKET (1") |
| 13 |
94909 |
BEARING BLOCK, DRIVE SHAFT (LONG SHAFT) |
▶FLYWHEEL, STATOR AND MANUAL STARTER (48 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
247-7933A2 |
FLYWHEEL ASSEMBLY |
| 2 |
28-20094 |
KEY, FLYWHEEL DRIVE |
| 3 |
12-20553 |
WASHER, FLYWHEEL |
| 4 |
11-8M0204726 |
NUT, FLYWHEEL |
| 5 |
339-5566A5 |
STATOR ASSEMBLY |
| 6 |
10-66707 |
SCREW, STATOR TO MOUNTING BRACKET (7/8") |
| 7 |
339-5590A1 |
COIL ASSEMBLY (3 3/8" AND 4 3/8" LEADS) |
| 8 |
54-59538 |
CLIP, COIL RETAINING |
| 9 |
54-65927 |
CLIP, COIL RETAINING |
| 10 |
86-69348 |
TERMINAL BLOCK, STATOR |
| 10A |
13-58308 |
LOCKWASHER, TERMINAL BLOCK |
| 11 |
10-22654 |
SCREW, LEADS TO TERMINAL BLOCK (3/8") |
| 12 |
10-69347 |
SCREW, TERMINAL BLOCK TO STATOR (5/8") |
| 13 |
11-46438 |
NUT, TERMINAL BLOCK SCREW |
| 14 |
70426A3 |
TRIGGER ASSEMBLY |
| 17 |
70414 |
LINK ROD, TRIGGER TO SPARK LEVER |
| 18 |
11-68219 |
NUT, ADJUSTING LINK ROD |
| 19 |
33973 |
SWIVEL BOLT, LINK ROD |
| 20 |
70428 |
BRACKET, STATOR MOUNTING |
| 21 |
10-25764 |
SCREW, STATOR MOUNTING BRACKET (7/16") |
| 22 |
70422 |
LEVER, SPARK |
| 23 |
10-62802 |
SCREW, ADJUSTING - SPARK LEVER (1 1/8") |
| 24 |
11-21923T |
NUT, ADJUSTING SCREW |
| 25 |
24-70418 |
SPRING, THROTTLE LEVER |
| 26 |
70424 |
THROTTLE LEVER |
| 27 |
70429 |
THROTTLE CAM |
| 28 |
10-38055 |
SCREW Comment: THROTTLE CAM TO THROTTLE LEVER (5/8") |
| 29 |
12-8M0204666 |
WASHER, THROTTLE CAM SCREW (7/8") |
| 30 |
10-38515 |
SCREW, SHOULDER (7/8") |
| 31 |
12-69056 |
WASHER, SHOULDER SCREW |
| 32 |
24-70167 |
SPRING, STARTER REWIND |
| 33 |
75764 |
BRACKET ASSEMBLY, STARTER REWIND |
| 34 |
10-37571 |
SCREW, BRACKET TO CYLINDER BLOCK (1/2") |
| 34A |
12-30164 |
WASHER, BRACKET TO CYLINDER BLOCK SCREW |
| 35 |
77568 |
STARTER SHEAVE |
| 36 |
50-90892A2 |
STARTER ROPE ASSEMBLY (INCLUDES 2 RIVETS) |
| 37 |
70396 |
HANDLE, STARTER ROPE |
| 38 |
70394 |
CAP, STARTER HANDLE |
| 39 |
75764A2 |
PINION, STARTER REWIND |
| 39A |
12-30164 |
WASHER, PINION |
| 40 |
24-70288 |
SPRING, PINION |
| 41 |
72697 |
RETAINER, PINION SPRING |
| 42 |
24-77511 |
SPRING, TORSION - PINION |
| 43 |
77512 |
HOLDER, SPRING |
| 44 |
23-78894 |
SPACER, SPRING HOLDER Comment: (SERIAL #9189790 AND UP) |
| 45 |
10-70181 |
SCREW, SPRING RETAINER (5/8") |
| 46 |
12-8M0204666 |
WASHER, SPRING RETAINER |
| 47 |
17-70180 |
RIVET, STARTER SHEAVE |
▶FUEL TANK, FUEL LINES AND CARBURETOR (41 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
1248-8083A2 |
FUEL TANK (SERIAL #9191589 AND UP) |
| 2 |
10-70298 |
SCREW, VENT - FUEL CAP |
| 3 |
12-8M0204663 |
WASHER, VENT SCREW |
| 4 |
36-78573A1 |
CAP, FUEL SERIAL Comment: SERIAL #9191589 AND UP |
| 5 |
27-78577 |
GASKET, FUEL CAP Comment: SERIAL #9191589 AND UP |
| 6 |
12-38255 |
WASHER, FUEL CAP |
| 7 |
24-22227 |
SPRING, FUEL CAP |
| 8 |
12-71055 |
WASHER, FUEL CAP |
| 9 |
18-210711 |
PIN, FUEL CAP - RING |
| 10 |
752373 |
CHAIN, FUEL CAP |
| 11 |
24-85767 |
SPRING, FUEL CAP - RETAINING Comment: SERIAL #9191589 AND UP |
| 12 |
27-78578 |
GASKET, FUEL TANK TO COWL Comment: SERIAL #9191589 AND UP |
| 13 |
78579 |
BRACKET, FUEL TANK AND IGNITION COIL Comment: SERIAL #9191589 AND UP |
| 14 |
10-37571 |
SCREW, BRACKET TO CYLINDER BLOCK (1/2") |
| 15 |
11-859124 |
NUT, BRACKET SCREW |
| 16 |
75689A1 |
STRAP ASSEMBLY, FUEL TANK ATTACHING |
| 16A |
10-26668 |
SCREW Comment: STRAP ASSEMBLY TO FUEL TANK BRACKET |
| 17 |
22-70997 |
FITTING, FUEL TANK (FILTER) |
| 18 |
54-68725 |
CLAMP, FUEL LINE TO FITTING |
| 19 |
32-8M0108355 |
FUEL LINE, FUEL TANK TO VALVE (8") |
| 20 |
54-68424 |
CLAMP, FUEL LINE ATTACHING |
| 21 |
20-70555 |
VALVE Comment: FUEL SHUT OFF (SERIAL #9191588 AND BELOW) |
| 22 |
32-8M0108355 |
FUEL LINE Comment: VALVE TO CARBURETOR (4" AND 1-1/2") |
| 23 |
22-19688 |
FITTING, CARBURETOR TO FUEL LINE (90 DEG.) |
| 24 |
89977A2 |
CARBURETOR |
| 25 |
27-70417 |
GASKET, CARBURETOR MOUNTING |
| 26 |
70557 |
CHOKE CABLE (SQUARE SHOULDER) |
| 27 |
77999 |
SPACER, CHOKE KNOB - INNER Comment: USE WITH ROUND SHOULDERED CHOKE |
| 28 |
78000 |
SPACER, CHOKE KNOB - OUTER Comment: USE WITH ROUND SHOULDERED CHOKE |
| 29 |
11-78045 |
NUT, LOCKING - CHOKE CABLE |
| 30 |
86874 |
KNOB, CHOKE CABLE |
| 31 |
12-8M0204649 |
WASHER, CARBURETOR STUD |
| 32 |
11-36069 |
NUT, CARBURETOR STUD |
| 33 |
35-76934 |
FUEL FILTER |
| 34 |
78049 |
LEVER, IDLE ADJUSTMENT |
| 35 |
78046 |
LINK, IDLE ADJUSTMENT |
| 36 |
78048 |
SHAFT, IDLE ADJUSTMENT |
| 38 |
23-78047 |
SLEEVE, IDLE ADJUSTMENT |
| 40 |
11-78045 |
NUT, CHOKE KNOB |
| 41 |
76623 |
BRACKET, FUEL TANK (LONG SHAFT) |
▶GEAR HOUSING ASSEMBLY (DRIVE SHAFT) (34 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
1648-7381A1 |
GEAR HOUSING ASSEMBLY, BASIC |
| 2 |
16-75321 |
STUD, GEAR HOUSING (7 1/4") - LONG SHAFT |
| 3 |
16-68928 |
STUD, WATER PUMP (2 1/4') |
| 4 |
16-70741 |
STUD, WATER PUMP (1 1/2") |
| 5 |
31-23101 |
ROLLER BEARING, GEAR HOUSING - LOWER |
| 6 |
68978 |
COUPLING, DRIVE SHAFT/PINION |
| 7 |
31-69496 |
ROLLER BEARING, GEAR HOUSING - UPPER |
| 8 |
43-68981 |
PINION GEAR |
| 9 |
31-68945 |
THRUST BEARING, PINION GEAR |
| 10 |
12-71557 |
WASHER, THRUST BEARING |
| 11 |
45-75310 |
DRIVE SHAFT (LONG SHAFT) |
| 12 |
28-8M0032835 |
KEY, IMPELLER DRIVE |
| 13 |
27-68939 |
GASKET, WATER PUMP - LOWER |
| 14 |
46-90844A1 |
WATER PUMP HOUSING ASSEMBLY |
| 15 |
26-897153 |
OIL SEAL, WATER PUMP |
| 16 |
70977T |
INSERT, WATER PUMP |
| 17 |
12-8M0204666 |
WASHER, WATER PUMP |
| 18 |
25-74138 |
QUAD SEAL, WATER PUMP |
| 19 |
47-89980 |
IMPELLER |
| 20 |
68955 |
FACE PLATE, WATER PUMP |
| 21 |
46-95965A2 |
WATER PUMP COVER ASSEMBLY |
| 22 |
26-30913 |
OIL SEAL, WATER PUMP COVER |
| 23 |
23-13127 |
WASHER, WATER TUBE SEAL |
| 24 |
26-36558 |
SEAL, WATER TUBE |
| 24A |
23-31792T |
SLEEVE, WATER TUBE GUIDE |
| 25 |
25-30526 |
RING, RUBBER - DRIVE SHAFT |
| 26 |
12-30164 |
WASHER, WATER PUMP STUDS |
| 27 |
11-859124 |
NUT, WATER PUMP STUDS |
| 28 |
75307 |
SHIFT SHAFT (LONG SHAFT) |
| 29 |
10-28653 |
SCREW, VENT - GEAR HOUSING (1/4") |
| 30 |
19643 |
WASHER, VENT SCREW |
| 31 |
10-79953Q04 |
SCREW, GREASE FILLER |
| 32 |
12-191833 |
WASHER, GREASE FILLER SCREW |
▶GEAR HOUSING ASSEMBLY (PROPELLER SHAFT) (23 parts)
| Ref |
OEM Part # |
Part Name |
| - |
27-77586A78 |
GASKET SET |
| 1 |
1648-7381A1 |
GEAR HOUSING ASSEMBLY |
| 33 |
11-20696 |
NUT, PROPELLER SHAFT |
| 34 |
12-73672 |
WASHER, PROPELLER SHAFT |
| 35 |
43-68980 |
DRIVE GEAR |
| 36 |
24-91813 |
SPRING, CLUTCH |
| 37 |
15-69516A1 |
SHIM ASSEMBLY, BALL BEARING |
| 38 |
30-70894 |
BALL BEARING, DRIVE GEAR |
| 39 |
11-69515 |
NUT, DRIVE GEAR |
| 40 |
44-68982 |
PROPELLER SHAFT |
| 41 |
75816 |
SPACER, PROPELLER SHAFT Comment: SERIAL #9210546 AND UP |
| 42 |
99210A1 |
BEARING CARRIER ASSEMBLY Comment: SERIAL #9210546 AND UP |
| 43 |
31-21145 |
ROLLER BEARING Comment: SERIAL #9210545 AND BELOW |
| 44 |
26-98309 |
OIL SEAL Comment: SERIAL #9210546 AND UP |
| 45 |
75812 |
COVER, GEAR HOUSING Comment: SERIAL #9210546 AND UP |
| 46 |
25-68935 |
"O" RING, BEARING CARRIER |
| 47 |
28-32003 |
KEY, BEARING CARRIER |
| 48 |
12-68923 |
WASHER, GEAR HOUSING COVER Comment: SERIAL #9141798 AND BELOW |
| 49 |
70588 |
THRUST HUB, FORWARD |
| 50 |
48-86903A1 |
PROPELLER ASSEMBLY |
| 51 |
70589 |
THRUST HUB, AFT |
| 52 |
11-82670911 |
NUT, PROPELLER |
| 53 |
11-82670911 |
NUT, DRIVE SHAFT HOUSING STUD |
▶MISCELLANEOUS PARTS/ACCESSORIES (1 parts)
| Ref |
OEM Part # |
Part Name |
| - |
75311A1 |
CONVERSION KIT Comment: (SHORT SHAFT TO LONG SHAFT) |
▶STEERING HANDLE ASSEMBLY (19 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
11099A1 |
BOOT ASSEMBLY, HANDLE |
| 2 |
70382 |
GRIP, HANDLE |
| 3 |
70383 |
ARM, HANDLE |
| 4 |
12-31433 |
WASHER, HANDLE |
| 5 |
53-70384 |
RETAINING RING, HANDLE |
| 6 |
70386 |
PULLEY, STEERING CABLE |
| 7 |
70385 |
SHAFT, HANDLE |
| 7A |
84-70671A1 |
HARNESS ASSEMBLY, STOP SWITCH |
| 8 |
70389A2 |
BRACKET ASSEMBLY, HANDLE |
| 9 |
10-37978 |
SCREW, HANDLE BRACKET (3/4") |
| 10 |
70390 |
RETAINER, CABLE |
| 11 |
85-708571 |
INSULATOR, CABLE |
| 12 |
23-70391 |
BUSHING, HANDLE BRACKET |
| 13 |
11-73784 |
NUT, HANDLE BRACKET |
| 14 |
92791 |
CABLE, THROTTLE ADVANCE |
| 15 |
92791 |
CABLE, THROTTLE RETARD |
| 16 |
11-21825 |
NUT, THROTTLE CABLE |
| 17 |
12-37998 |
WASHER, THROTTLE CABLE |
| 18 |
32-9912688 |
SLEEVE, STOP SWITCH HARNESS |
▶SWITCH BOX AND IGNITION COIL (14 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
339-6222A8 |
SWITCH BOX ASSEMBLY |
| 2 |
10-45218 |
SCREW, SWITCH BOX GROUND (3/8") |
| 3 |
10-22523 |
SCREW, SWITCH BOX (3/4") |
| 3A |
23-26731 |
SPACER, SWITCH BOX SCREW (EARLY MODELS) |
| 4 |
12-8M0204666 |
WASHER, SWITCH BOX SCREW |
| 5 |
54-63153 |
"J" CLIP, SWITCH BOX LEAD |
| 6 |
33-813472 |
SPARK PLUG (USE IN BELGIUM AND CANADA) |
| 7 |
33-813472 |
SPARK PLUG (USE IN UNITED STATES) |
| 8 |
300-8M0166172 |
IGNITION COIL ASSEMBLY |
| 10 |
11-45076 |
NUT, IGNITION COIL TERMINAL |
| 11 |
76254 |
COIL COVER |
| 12 |
10-76502 |
SCREW, COIL COVER (1 7/8") |
| 13 |
61990 |
STA-STRAP, SWITCH BOX LEADS |
| 14 |
5790811 |
SLEEVE, SWITCH BOX LEADS |
▶TOP COWL (15 parts)
| Ref |
OEM Part # |
Part Name |
| 1 |
2155-6654 |
TOP COWL (SERIAL #9191589 AND UP) Comment: DOES NOT INCLUDE DECALS |
| 2 |
74139 |
HOOK, TOP COWL - REAR |
| 3 |
10-45742 |
SCREW, HOOK TO COP COWL (3/8") |
| 4 |
11-8M0204718 |
NUT, HOOK SCREW |
| 5 |
70461 |
CATCH, TOP COWL - FRONT |
| 6 |
10-69570 |
SCREW, CATCH TO COP COWL (3/4") |
| 7 |
78634 |
SOUND BOX (SERIAL #9141799 AND UP) |
| 7A |
22-390721 |
PLUG, SOUND BOX |
| 8 |
10-52195 |
SCREW, SOUND BOX TO CARBURETOR (1/2") |
| 9 |
12-20192 |
WASHER, SOUND BOX SCREW |
| 10 |
27-70289 |
GASKET, SOUND BOX Comment: NOT USED ON LATER MODELS |
| 11 |
70292 |
COVER, SOUND BOX Comment: NOT USED ON LATER MODELS |
| 12 |
19-824928001 |
PLUG, SOUND BOX Comment: NOT USED ON LATER MODELS |
| 13 |
10-95700 |
SCREW, COVER TO SOUND BOX (1/2") Comment: NOT USED ON LATER MODELS |
| 14 |
10-72415 |
SCREW, SOUND BOX TO COVER (1") |
100-Hour / Annual Service Checklist
Regular maintenance keeps your Mercury 40, 4 (GNAT 2 CYL.) running reliably season after season. Most of these tasks can be performed with basic tools and the factory service manual.
- Replace water pump impeller and inspect wear plate
- Change engine oil and oil filter (check drain plug washer)
- Replace spark plugs and check ignition timing
- Drain and refill lower unit gear oil; inspect for water contamination
- Inspect fuel lines, primer bulb, and fuel filter for deterioration
- Check and replace sacrificial anodes (zinc or aluminum)
- Inspect propeller for damage; check shaft seal and cotter pin
- Check valve clearance (refer to service manual for specifications)
- Lubricate all grease points (steering, tilt tube, shift linkage)
- Inspect control cables and throttle/shift linkage for smooth operation
-
Pro Tip: Always flush the engine with fresh water after saltwater use — even a quick 10-minute flush significantly extends component life.
-
Pro Tip: Use fuel stabilizer in the tank before winter storage, and fog the cylinders to prevent internal corrosion during extended periods of non-use.
