Mercury 250 (3.0L EFI) (1B417702 THRU 1B504988) Parts & Diagrams

OEM and aftermarket replacement parts for Mercury 250 (3.0L EFI). Scroll down for exploded parts diagrams (33), specifications, and maintenance reference.

Mercury 250 (3.0L EFI) (1B417702 THRU 1B504988) Parts & Diagrams

🔎 Mercury 250 (3.0L EFI) Reference Library — Exploded parts diagrams (33 diagrams), specifications, common issues, and maintenance checklist.

The Mercury 250 (3.0L EFI) is a 4-Stroke, V8 64-degree, DOHC, 32-valve outboard motor. Designed for large center-consoles, offshore sport-fishing boats, and multi-engine configurations.

Quick Reference Specifications

Specification Value
Engine Type 4-Stroke, V8 64-degree, DOHC, 32-valve
Horsepower 250 HP
Displacement 4600 cc (4.6L / 279 CID)
Bore x Stroke 92 mm x 86 mm (3.62 in. x 3.38 in.)
Spark Plug (Type & Gap) NGK LKAR7C-9
Engine Oil Capacity 7.0 L (7.4 qt)
Recommended Engine Oil Mercury FourStroke Oil 25W-40 (NMMA FC-W SAE 10W-30)
Gear Case Oil Capacity 802 mL (27.1 oz)
Idle Speed (in gear) 600 RPM
Full Throttle RPM Range 5200-6000
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 250 (3.0L EFI):

  • 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 250 (3.0L EFI).

Accessories (1 parts) Accessories
Ref OEM Part # Part Name
0 858915A1 TRIM REDUCER KIT
Attenuator/Flywheel Cover (14 parts) Attenuator/Flywheel Cover
Ref OEM Part # Part Name
1 892854T01 COVER, Flywheel
2 25-13467 GROMMET, (.88 Inside Diameter)
3 25-8M0153609 GROMMET
4 19-89219001 PLUG
5 881909T3 ATTENUATOR ASSEMBLY
6 23-856954 BUSHING
7 25-8M0190980 GROMMET
8 882767 SEAL
9 25-20116 GROMMET
10 54-23567 CLIP
11 12-65567 WASHER, (.265 x .750 x .048) Stainless Steel
12 10-82130025 SCREW, (M6 x 25)
13 37-881865 DECAL, Caution-Start in Gear
14 10-69570 SCREW, (#10-16 x .750)
Bottom Cowl (25 parts) Bottom Cowl
Ref OEM Part # Part Name
1 100-8M0107324 BOTTOM COWL, Port
2 854367001 PLUG
3 100-8M0107323 BOTTOM COWL, Starboard
4 27-889246A97 GASKET KIT
5 10-82130040 SCREW, (M6 x 40)
6 10-824868 SCREW, (M6 x 75)
7 12-8M0204649 WASHER, (.281 x .500 x .060) Stainless Steel
8 8M0053903 FRONT HANDLE
9 23-335891 BUSHING
10 25-48462 O-RING, (.614 x .070)
11 8219423 PAWL
12 12-69057 WASHER, (.281 x .734 x .063)
13 11-401366 NUT, (M6) Stainless Steel
14 10-8214281 SCREW, (#10-16 x .625)
15 54-822873 CLIP
16 87-8M0235191 SWITCH, Trim
17 8M8027677 RIGGING KIT (Upper)
18 NSS NOT SOLD SEPARATE, Clamp-Lower
19 10-82130012 SCREW, (M6 x 12)
20 NSS NOT SOLD SEPARATE, Strap
21 859343 FOAM
22 54-850181 TIE STRAP, (11.750 Inches)
23 852361T02 HANDLE Comment: SN# 1B447000 & Up
24 13-29402 WAVE WASHER Comment: SN# 1B446999 & Below
25 8M0109218 SEAL, (44.00 Inches)
Coil Plate (21 parts) Coil Plate
Ref OEM Part # Part Name
- 879346A51 HARNESS ASSEMBLY, 5 Pin
1 850295T2 PLATE, Coil Mounting
2 300-8M0077471 COIL KIT
3 10-82129130 SCREW, (M6 x 30)
4 84-881908T CABLE SET
5 54-828991T CLIP (Included with Coil Harness)
6 33-941 SPARK PLUG
7 84-882757T02 HARNESS ASSEMBLY, Coil
8 84-858414A1 CABLE ASSEMBLY, Braided
9 10-82129110 SCREW, (M6 x 10)
10 12-8M0204649 WASHER, (.281 x .500 x .060) Stainless Steel
11 25-833155 GROMMET
12 12-4002318 WASHER
13 23-8502341 BUSHING
14 10-81893435 SCREW, (M8 x 35)
15 71-8M0157742 SENSOR KIT, (0-50 PSI)
16 22-8M0207782 FITTING
17 54-883066 CLIP, (.865)
18 54-816311T TIE STRAP, (8.00 Inches)
19 32-85978571 TUBING, (52.00 Inches Bulk) (Cut to 18 Inches)
20 12-36001 WASHER
Crankshaft, Pistons and Connecting Rods (23 parts) Crankshaft, Pistons and Connecting Rods
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 482-9784A11 CRANKSHAFT ASSEMBLY
2 NSS NOT SOLD SEPARATE, Wear Sleeve
3 30-67923T BEARING, Ball (Lower)
4 53-67446 RING
5 39-843198T01 RING, Seal
6 28-91800 KEY, Woodruff
7 25-35126 O-RING, (.859 x .139)
8 31-88270A02 BEARING/RACE KIT
9 NSS NOT SOLD SEPARATE, Bearing-Center Main
10 700-878573A2 PISTON ASSEMBLY Comment: (Port - .030 oversize)
11 40-841202 RING
12 39-858772A12 RING SET, Piston
13 NSS NOT SOLD SEPARATE, Piston Ring-Lower
14 600-8M0125869 CONNECTING ROD ASSEMBLY
15 10-94320 SCREW, (.375-24 x 1.250)
16 31-844338A01 BEARING/CAGE KIT
17 NSS NOT SOLD SEPARATE, Needle Roller Bearing
18 12-88263 THRUST WASHER
19 29-8M0204715 BEARING, Needle
20 31-816773A2 BEARING ASSEMBLY (Upper)
21 26-859093 SEAL
22 25-823683 O-RING, (1.989 x .070)
Cyliner Block and End Cap (64 parts) Cyliner Block and End Cap
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 885-899162A07 CYLINDER BLOCK ASSEMBLY Comment: (250)
2 10-81893440 SCREW, (M8 x 40)
3 8M0111325 BRACKET
4 16-903509 STUD, (M10 x 1.5 x 64)
5 16-8154431 STUD, (M10 x 1.5 x 155)
6 8248577 DEFLECTOR
7 21-8781051 CHECK VALVE
8 17-8M0036405 PIN
9 17-43044 PIN, Dowel - Without Hole (.375 x .625)
10 10-82446180 SCREW, (M10 x 80)
11 10-81893435 SCREW, (M8 x 35)
12 10-81893420 SCREW, (M8 x 20)
13 17-63779 PIN, Dowel (.250 x .625)
14 13536A13 SENSOR ASSEMBLY, Temperature
15 17-8405101 PIN
16 8588641 RETAINER
17 12-8M0214963 WASHER, (.406 x .750 x .105) Stainless Steel
18 11-4013610 NUT, (M10) Stainless Steel
19 8M0082988 SENSOR
20 10-40011107 SCREW, (M5 x 16) Stainless Steel
21 1171-9787A4 END CAP ASSEMBLY
22 25-62700 O-RING, (3.237 x .103)
23 26-8308981 SEAL
24 10-82130020 SCREW, (M6 x 20)
25 857186T02 PLATE ASSEMBLY
26 23-855729 MOUNT
27 10-82130145 SCREW, (M10 x 45)
28 10-82494810 SCREW, (M6 x 10)
29 25-19565002 GROMMET
30 12-855725 WASHER
31 137151 RETAINER
32 54-858951 J CLIP
33 10-82130012 SCREW, (M6 x 12)
34 818574 SEAL
35 812851A27 CYLINDER HEAD ASSEMBLY
36 884391 SEAL
37 8M0057307 THERMOSTAT, 54 Degree C/130 Degree F
38 27-8503181 GASKET
39 8M0039357 COVER, Thermostat
40 10-82130025 SCREW, (M6 x 25)
41 10-8M0045380 SCREW, (M8 x 50)
42 8M0148668 SENSOR ASSEMBLY
43 25-896699 O-RING, (1.78 mm x .08 mm)
44 10-81893414 SCREW, (M8 x 14)
45 22-782792 FITTING, Elbow 45 Degree (1.25)
46 8583561 LEVER, TPI
47 10-82130025 SCREW, (M6 x 25)
48 23-856954 BUSHING
49 25-8M0190980 GROMMET
50 12-65567 WASHER, (.265 x .750 x .048) Stainless Steel
51 10-40011113 SCREW, (M5 x 45) Stainless Steel
52 8M6005165 INDICATOR, Throttle Position
53 8M0084743 LINK
54 54-858902 CLAMP
55 8582261 COVER
56 8544862 BRACKET
57 54-855228 CLAMP, (25.6 mm)
58 22-8533394 FITTING
59 32-8404461 HOSE (Starboard)
60 32-8404462 HOSE (Port)
61 8M6003194 SENSOR ASSEMBLY, Knock Comment: (200)
62 16-882781 STUD Comment: (200)
63 11-826292 NUT, (M10) Brass/Nickel Plated Comment: (200)
Deck Oil Fill Kit, 15969A3 or 15969A5 (9 parts) Deck Oil Fill Kit, 15969A3 or 15969A5
Ref OEM Part # Part Name
1 15969A3 DECK FILL KIT, Oil, With Hose
2 15969A13 DECK FILL KIT, Oil, With Out Hose
3 15966 PLATE
4 15969A08 DECK PLATE ASSEMBLY
5 10-16324 SCREW, (#8 x .625)
6 54-815504228 CLAMP, Worm Gear
7 15967 ADAPTOR, Oil Filler
8 25-11332 O-RING, (2.225 x .210)
9 32-850719 HOSE, (100.00 Feet Bulk) , Oil Filler - Cut as Required
Driveshaft Housing and Exhaust Tube (32 parts) Driveshaft Housing and Exhaust Tube
Ref OEM Part # Part Name
1 3519-832938A06 HOUSING ASSEMBLY, Driveshaft Comment: (X-Long/XX-Long)
2 16-8M0008031 STUD, (M12 x 52) Comment: (Long/X-Long)
3 10-857136 SCREW, (M12 x 35 MM) Comment: (Long/X-Long)
4 25-8331231 GROMMET
5 12-856982 WASHER, (.500 x .810 x .090) Stainless Steel
6 11-896895 NUT, (M12)
7 19-64649 PLUG
8 10-898834 BOLT, (M14 x 178)
9 88238A10 CABLE ASSEMBLY, Ground
10 12-815432 WASHER, (.562 x 2.00 x .125)
11 12-8154331 WASHER, (1.25 x 2.00 x .19)
12 8137711 MOUNT
13 12-825190 WASHER
14 11-896602 NUT, (M14)
15 8186442 CLAMP
16 10-81893435 SCREW, (M8 x 35)
17 13-72521 LOCKWASHER, Internal Tooth
18 8M0001136 COVER, Lower Mount
19 10-69079 SCREW, (#10-16 x .440)
20 8329321 SEAL
21 833116A4 TUBE ASSEMBLY, Exhaust
22 35-8M0026113 STRAINER
23 10-81893435 SCREW, (M8 x 35)
24 32-8M0042787 TUBE, Water Comment: (XX-Long)
25 832940001 SEAL
26 8329391 CLAMP
27 10-41508 SCREW, (.250-20 x .500) Stainless Steel
28 8M0105088 SPACER Comment: (XX-Long)
29 17-43044 PIN, Dowel - Without Hole (.375 x .625) Comment: (XX-Long)
30 16-8M0008047 STUD, (M12 x 179) Comment: (XX-Long)
31 10-857137 SCREW, (M12 x 160) Comment: (XX-Long)
32 10-81893435 SCREW, (M8 x 35)
Dual Engine Tie Bar Kit (21 parts) Dual Engine Tie Bar Kit
Ref OEM Part # Part Name
- 92876A9 EXTENSION KIT, Dual Engine
1 71565A2 TUBE ASSEMBLY
2 25-48462 O-RING, (.614 x .070)
3 41055 MOUNT
4 14-42100 TAB WASHER
5 11-8M0041651 NUT, (.875-14)
6 88404 TAB WASHER
7 10-38601 SCREW, (.250-28 x 1.250)
8 17729A1 BRACKET
9 10-62055 SCREW, (.312-24 x 1.250)
10 17728 TAB WASHER
11 10-140001 SCREW, (.375-24 x 1.38)
12 11-8M0204726 NUT, (.375-24) Stainless Steel
13 8M0026167 STEERING EYE
14 23-23651 SLEEVE, (1.625)
15 97931 TUBING, (4.00 Inches)
16 8M0026098 COUPLER, 15 In.
17 11-42099 NUT, (.562-18)
18 22-821169 COUPLING
19 12-37828 WASHER, (.390 x .625 x .062) Stainless Steel
20 10-94319 SCREW, (.375-24 x 1.5)
Exhaust Plate (46 parts) Exhaust Plate
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 832935A17 PLATE ASSEMBLY, Exhaust
2 27-8329335 GASKET
3 27-8329344 GASKET (Lower)
4 8M0043157 SEAL
5 22-8320761 FITTING, Check Valve
6 22-8M0180565 PLUG, Pipe (.375-18) Brass
7 21-817519A1 CHECK VALVE ASSEMBLY, Drain
8 17-43044 PIN, Dowel - Without Hole (.375 x .625)
9 25-822002 GROMMET
10 19-48323 PLUG
11 65663A2 COVER ASSEMBLY
12 10-81893435 SCREW, (M8 x 35)
13 814190 CARRIER
14 25-814191 GROMMET
15 814189 POPPET
16 24-64878 SPRING, (Black)
17 65664A1 PLATE ASSEMBLY
18 27-88907003 GASKET
19 648771 DIAPHRAGM
20 12-76451 WASHER
21 10-69570 SCREW, (#10-16 x .750)
22 10-81893435 SCREW, (M8 x 35)
23 850306A04 BOOT KIT, Idle Exhaust Comment: (Includes ref.'s 44 & 45)
24 54-850896 CLAMP, (28.6)
25 22-8M0077650 FITTING, Tell-Tale
26 19-821908 PLUG
27 12-821915 WASHER
28 22-8596001 FITTING
29 8219631 CHECK VALVE
30 25-30641 O-RING, (.299 x .103)
31 11-401386 NUT, (M6) Stainless Steel
32 883142A03 SHIFT LINK KIT
33 8539683 SLIDE
34 11-401386 NUT, (M6) Stainless Steel
35 23-42994 BUSHING
36 8240703 SHIFT SHAFT, Upper Comment: (XX-Long)
37 23-48237 BUSHING
38 43585 COUPLING
39 32-859626A1 FLUSH HOSE KIT (Inlet)
40 25-12602002 GROMMET
41 12-35459 WASHER
42 32-8M0108355 HOSE, (57.00 Inches Bulk) (Cut to 3 Inches)
43 22-858855 FITTING, Straight
44 888910 PLATE
45 10-82239312 SCREW, (M5 x 12)
Flywheel/Alternator (19 parts) Flywheel/Alternator
Ref OEM Part # Part Name
1 8M6013461 ALTERNATOR
2 24-8523742 SPRING
3 856815T2 ARM TENSIONER ASSEMBLY
4 12-4002320 WASHER
5 23-8568941 BUSHING
6 16-8M0034457 STUD, (M10 x 85)
7 11-826292 NUT, (M10) Brass/Nickel Plated
8 8M6005030 PULLEY ASSEMBLY
9 10-4010835 SCREW, (M10 x 35) Hex Flange - Stainless Steel
10 57-828507Q11 BELT
11 283-859619T1 FLYWHEEL
12 11-42979 NUT, (M16)
13 12-33001 WASHER, (.641 x 1.250 x .190)
14 19-45907 PLUG, Yellow
15 11-401386 NUT, (M6) Stainless Steel
16 84-856583A5 CABLE ASSEMBLY
17 12-4002319 WASHER
18 10-82130150 SCREW, (M10 x 50)
19 10-82130012 SCREW, (M6 x 12)
Fuel Line Assembly (8 parts) Fuel Line Assembly
Ref OEM Part # Part Name
1 32-8M0044837 HOSE ASSEMBLY, Fuel (12 Feet) Mercury Branded Comment: (2009 and Up)
2 32-8M0038500 HOSE, (100.00 Feet Bulk) Comment: (2009 and Up)
3 13330Q07 BULB ASSEMBLY, Primer (Yellow Washer)
4 21-13331A3 CHECK VALVE ASSEMBLY, Inlet
5 21-13331A4 CHECK VALVE ASSEMBLY, Outlet
6 54-4158210 CLAMP, Nylon, Large
7 54-41582Q7 CLAMP, Nylon, Small
8 54-815504104 CLAMP, Worm Gear
Fuel Management (57 parts) Fuel Management
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 883951T1 ADAPTOR PLATE
2 27-804680 GASKET
3 828623T4 REED BLOCK
4 10-8555252 SCREW, (M6)
5 23-855364 BUSHING
6 25-855362001 GROMMET
7 10-81893435 SCREW, (M8 x 35)
8 12-817274 WASHER, (.344 x 1.00 x .063) Stainless Steel
9 10-81893430 SCREW, (M8 x 30)
10 883950T1 PLENUM KIT, Air
11 27-804679004 GASKET
12 10-1993716 SCREW, (M6 x 16)
13 884522 BRACKET, MAP Sensor
14 854445 SENSOR, MAP
15 8M0148668 SENSOR ASSEMBLY
16 25-896699 O-RING, (1.78 mm x .08 mm)
17 883949T1 THROTTLE BODY KIT
18 10-82130040 SCREW, (M6 x 40)
19 25-855426 O-RING
20 858851A03 LEVER ASSEMBLY, Throttle
21 8M0072162 ROLLER
22 12-8M0204666 WASHER, (.203 x .500 x .032)
23 8-32,11-826709104 NUT, Stainless Steel
24 10-889354 SCREW, Special
25 12-881991 WASHER, Cupped
26 12-881992 WASHER, Spool
27 10,13-69432 LOCKWASHER, External
28 858353A08 CAM ASSEMBLY
29 8235694 BALL, Threaded
30 23-8M0215006 BUSHING
31 23-8807371 BUSHING
32 10-40011155 SCREW, (M8 x 55) Stainless Steel
33 12-56720 WASHER, (.330 x .750 x .060) Stainless Steel
34 22-993211 FITTING
35 8M0185615 PUMP ASSEMBLY
36 883926 BRACKET
37 10-883942 SCREW, (M4 x 16)
38 10-82130025 SCREW, (M6 x 25)
39 12-8M0214930 WASHER
40 25-8M0190980 GROMMET
41 23-822003 BUSHING
42 883952T1 FUEL RAIL
43 8833821 RETAINER
44 10-840118 SCREW, (#8-32 x .380)
45 840481T01 INJECTOR ASSEMBLY
46 25-895239A01 O-RING KIT
47 8832151 TUBE
48 25-883355 O-RING
49 22-883940 FITTING
50 10-883376 SCREW, (#10-24 x .375)
51 883382 RETAINER
52 25-20385 O-RING, (.239 x .070)
53 84-880745T1 HARNESS ASSEMBLY, Fuel Rail
54 54-883941 CLAMP
55 54-8M0024808 J CLIP (Use where Applicable)
56 10-82130040 SCREW, (M6 x 40)
Gear Housing(Driveshaft)(Standard/Counter Rotation) (46 parts) Gear Housing(Driveshaft)(Standard/Counter Rotation)
Ref OEM Part # Part Name
- 47-8M0100526 REPAIR KIT, Water Pump Impeller
1 1623-859399T18 GEAR HOUSING ASSEMBLY, Basic
2 17-379721 PIN
3 821526001 FILLER BLOCK
4 859402 PITOT TUBE
5 97-826134Q ANODE
6 10-4000333 SCREW, (M6 x 40)
7 11-401386 NUT, (M6) Stainless Steel
8 31-42647A1 BEARING ASSEMBLY, Roller
9 17-43044 PIN, Dowel - Without Hole (.375 x .625)
10 10-79953Q04 SCREW KIT, (.375-16 x .250) Drain
11 26-8M0204693 SEAL
12 22-881866 FITTING
13 10-1993716 SCREW, (M6 x 16)
14 858934 COVER
15 27-858935 GASKET
16 NSS NOT SOLD SEPARATE, Pinion Gear (1.75:1 - 12/21)(Part of 43-859321A3 or 43-828695A1)
17 12-92721 WASHER
18 11-35921 NUT, (.625-18)
19 26-8M0204708 SEAL, Oil
20 25-896522 O-RING, (799 x .103)
21 10-1993716 SCREW, (M6 x 16)
22 12-77674 WASHER
23 824145 SHIFT SHAFT
24 45-881943 DRIVESHAFT Comment: (XX-Long)
25 15-8M0063268 SHIM ASSEMBLY
26 31-8M0146553 BEARING, Tapered Roller
27 NSS NOT SOLD SEPARATE, Cup
28 28-8M0204723 KEY
29 15-42637A1 SHIM SET
30 31-8M0146566 BEARING ASSEMBLY, Roller/Cup
31 NSS NOT SOLD SEPARATE, Cup
32 8245191 RETAINER
33 8M0214948 CARRIER ASSEMBLY
34 25-8M0142854 O-RING, (2.175 x .103)
35 26-8M0214939 SEAL, Oil
36 26-8M0214939 SEAL, Oil
37 817275A2 HOUSING KIT, Upper Water Pump
38 26-816575A2 SEAL KIT
39 27-430331 GASKET
40 27-8172771 GASKET
41 8M0204709 FACEPLATE
42 47-43026T2 IMPELLER
43 832942A1 COUPLING ASSEMBLY
44 25-8M0204645 O-RING, (.796 x .139)
45 25-8M0204654 O-RING, (1.046)
Gear Housing, Propeller Shaft - Counter Rotation (40 parts) Gear Housing, Propeller Shaft - Counter Rotation
Ref OEM Part # Part Name
- 26-816575A4 SEAL KIT, Gear Housing
1 1623-859399T18 GEAR HOUSING ASSEMBLY, Basic
2 22-859403 PLUG
3 8M0226861 SHIFT CRANK
4 8M0235940 SPOOL ASSEMBLY
5 NSS NOT SOLD SEPARATE, Spool
6 NSS NOT SOLD SEPARATE, Sleeve
7 18-469501 COTTER PIN
8 15-44491A1 SHIM SET
9 828830A2 ADAPTOR ASSEMBLY, Bearing
10 31-814653T BEARING ASSEMBLY, Needle Rollers
11 12-815481 THRUST WASHER
12 31-815480 BEARING, Thrust
13 43-828696T2 GEAR, Reverse (12/21)
14 31-15844 BEARING ASSEMBLY, Roller
15 24-30893 SPRING
16 52-859340T CLUTCH
17 17-8M0100263 PIN, Cross
18 17-828356 PIN, Detent
19 44-8M0140448 PROPELLER SHAFT
20 43-828695A1 GEAR SET, Forward/Pinion (12/21)
21 23-1761526 SPACER SHIM, (.230)
22 31-815480 BEARING, Thrust
23 12-815481 THRUST WASHER
24 828831A3 ADAPTOR ASSEMBLY, Bearing
25 31-814653T BEARING ASSEMBLY, Needle Rollers
26 12-18448 THRUST WASHER
27 31-15842 BEARING, Thrust
28 8182911 RACE, Thrust
29 814605 KEEPER
30 25-8M0142840 O-RING, (3.850 x .210)
31 818290T8 CARRIER ASSEMBLY, Bearing
32 31-30956T BEARING, Needle
33 26-14077 SEAL, Oil (Inside)
34 26-8M0204670 SEAL (Outside)
35 14-18323 TAB WASHER
36 8M2011027 RETAINER
37 97-76214Q5 ANODE KIT
38 10-8M0204686 SCREW, (.437-14 x 1.750)
39 NSS NOT SOLD SEPARATE, Decal- Counter Rotation
Gear Housing, Propeller Shaft - Standard Rotation (32 parts) Gear Housing, Propeller Shaft - Standard Rotation
Ref OEM Part # Part Name
- 26-816575A4 SEAL KIT, Gear Housing
1 1623-859399T18 GEAR HOUSING ASSEMBLY, Basic
2 22-859403 PLUG
3 8M0226861 SHIFT CRANK
4 8M0235940 SPOOL ASSEMBLY
5 NSS NOT SOLD SEPARATE, Shift Spool
6 18-469501 COTTER PIN
7 NSS NOT SOLD SEPARATE, Sleeve
8 43-859321A3 GEAR SET, Forward/Pinion (12/21)
9 15-44491A1 SHIM SET
10 31-30894A1 BEARING SET, Cup And Cone
11 NSS NOT SOLD SEPARATE, Cup
12 53-856823 RING, Retaining
13 31-30895T BEARING, Needle
14 24-30893 SPRING
15 52-859340T CLUTCH
16 17-828356 PIN, Detent
17 17-8M0100263 PIN, Cross
18 44-8M0140440 PROPELLER SHAFT
19 43-859322A1 GEAR, Reverse (12/21)
20 23-824108 SPACER
21 681001 RING, Thrust
22 30-88957T BEARING, Ball
23 25-8M0142840 O-RING, (3.850 x .210)
24 818763T11 CARRIER ASSEMBLY, Bearing
25 31-30956T BEARING, Needle
26 26-14077 SEAL, Oil (Inside)
27 26-8M0204670 SEAL (Outside)
28 14-18323 TAB WASHER
29 8M2011027 RETAINER
30 97-76214Q5 ANODE KIT
31 10-8M0204686 SCREW, (.437-14 x 1.750)
Mercathode Kit (15 parts) Mercathode Kit
Ref OEM Part # Part Name
1 88334A2 MERCATHODE KIT
2 88334A4 MERCATHODE ASSEMBLY
3 10-22793 SCREW, (#9-14 x .875)
4 12-30164 WASHER, (.192 x .375 x .0312) Stainless Steel
5 10-32,11-45076 NUT, Brass
6 72958A5 ELECTRODE ASSEMBLY
7 25-8M0204645 O-RING, (.796 x .139)
8 10-87698 SCREW, (#10-16 x 1.250) Stainless Steel
9 97-72957A5 ANODE ASSEMBLY
10 25-8M0204645 O-RING, (.796 x .139)
11 10-87698 SCREW, (#10-16 x 1.250) Stainless Steel
12 88-8M0207796 FUSE, 20 Ampere
13 84-95084A10 CABLE ASSEMBLY, (5.00 Inches) Red
14 84-95084A13 CABLE ASSEMBLY, (64.00 Inches)
15 84-79138A8 CABLE ASSEMBLY, (72.00 Inches) Black
Oil Injection Components (20 parts) Oil Injection Components
Ref OEM Part # Part Name
1 1200-8M0119508 TANK ASSEMBLY
2 NSS NOT SOLD SEPARATE, Decal-Reservoir
3 10-58376 SCREW, (.164-18 x .375)
4 12-72761 WASHER, (.203 x .562 x .060) Stainless Steel
5 36-814449A3 CAP ASSEMBLY
6 27-42999T GASKET
7 87-856156T02 SWITCH ASSEMBLY
8 10-81893435 SCREW, (M8 x 35)
9 12-4002318 WASHER
10 25-855362001 GROMMET
11 23-855364 BUSHING
12 32-8M0108355 HOSE, (57.00 Inches Bulk) (Cut to 7 Inches)
13 54-816311T TIE STRAP, (8.00 Inches)
14 22-8M0207780 FITTING
15 32-875283 HOSE, (2.00 Inches)
16 35-875284T01 FILTER, Oil - In Line
17 32-875289 HOSE
18 22-858955 CONNECTOR
19 NSS NOT SOLD SEPARATE, Plug
20 32-892830053 HOSE, (24.00 Inches Braided) (Cut to 22 Inches)
Port Bleed System (13 parts) Port Bleed System
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 21-8282182 CHECK VALVE
2 22-8272011 PIPE PLUG
3 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 20-1/2 Inches)
4 21-8159234 CHECK VALVE
5 21-8592352 CHECK VALVE, 90 Degree (.0625-27)
6 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 13 Inches)
7 21-426585 CHECK VALVE
8 22-8272011 PIPE PLUG
9 54-23567 CLIP
10 10-878608 SCREW, (#10-16 x .500)
11 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 11 Inches)
12 32-892024122 TUBING, (240.00 Inches Bulk) (Cut to 22-1/2 Inches)
Power Trim Components (38 parts) Power Trim Components
Ref OEM Part # Part Name
- 855998A11 POWER TRIM ASSEMBLY, Complete
1 878265A4 TRIM MOTOR
2 NSS NOT SOLD SEPARATE, Armature
3 NSS NOT SOLD SEPARATE, End Frame
4 10-82494830 SCREW, (M6 x 30)
5 13-400256 LOCKWASHER, (M6)
6 8782451 DRIVESHAFT
7 878410A1 PO CHECK KIT
8 893929A01 MANUAL RELEASE ASSEMBLY Comment: (Includes Reference #26)
9 8M0142997 SHAFT KIT
10 17-878267 PIN
11 878235A03 TILT CYLINDER ASSEMBLY
12 878239A02 GUIDE KIT Comment: (Includes Reference #26)
13 8M0142999 O-RING KIT Comment: (Includes Reference #26)
14 8M0168219 SHOCK ROD KIT Comment: (Includes Reference #26)
15 8M0143000 PISTON ASSEMBLY, Memory
16 878406A02 REPAIR KIT, Check Valve Comment: (Includes Reference #26)
17 878414T01 PISTON ASSEMBLY
18 878413A1 PISTON ASSEMBLY
19 1100-8M0021648 GUIDE ASSEMBLY
20 878264A1 RESERVOIR KIT
21 19-811613 PLUG ASSEMBLY
22 10-4000327 SCREW, (M6 x 14)
23 12-4002315 WASHER
24 892251A01 PUMP KIT
25 878408A1 REPAIR KIT, Power Trim
26 17-821539 PIN, Trilobe
27 10-858771 SCREW, (M10 x 30)
28 12-4002319 WASHER
29 97-818298Q1 ANODE KIT
30 10-8M0204707 SCREW, (M6 x 25)
31 12-8M0204649 WASHER, (.281 x .500 x .060) Stainless Steel
32 99625002 SHAFT
33 8M0084613 C WASHER
34 54-26550 CLAMP
35 10-878609 SCREW, (#10-16 x .600)
36 32-828547353 CONDUIT, (.350 Inside Diameter x 3.00 Feet Bulk) (Cut to 12 Inches)
37 54-816311T TIE STRAP, (8.00 Inches)
Powerhead Gasket Set Components (2 parts) Powerhead Gasket Set Components
Ref OEM Part # Part Name
- 27-832934A00 GASKET SET, Powerhead
0 26-854639001 SEAL, Thermostat Comment: Not used for this application
Reservoir Kit-Remote Oil(15943A1) (16 parts) Reservoir Kit-Remote Oil(15943A1)
Ref OEM Part # Part Name
- 824954A1 BRACKET KIT, Oil Reservoir Hold Down Comment: (Includes ref. 2)
1 15943A2 TANK ASSEMBLY, Oil (1.8 Gallon Tank)
2 NSS NOT SOLD SEPARATE, BRACKET, Tank Mount Comment: (Also sold with Bracket Kit Below)
3 NSS NOT SOLD SEPARATE, HANDLE/ROPE
4 12323A1 CORD/HOOK KIT
5 12320 BRACKET, Hold Down
6 10-79968 SCREW, (#12-11 x .750)
7 36-43298A2 CAP ASSEMBLY, Oil Reservoir
8 NSS NOT SOLD SEPARATE, CORD
9 25-11332 O-RING, (2.225 x .210), Cap
10 816190A4 HOUSING ASSEMBLY, Adapter
11 36-43298A2 CAP ASSEMBLY, Housing Adaptor
12 25-11332 O-RING, (2.225 x .210)
13 32-99802 TUBE, Oil Pick Up
14 32-99439 HOSE, (114.00 Inches)
15 54-816311T TIE STRAP, (8.00 Inches)
Service/Support Material (1 parts) Service/Support Material
Ref OEM Part # Part Name
- 37-804670A06 DECAL, EPA Label Information Comment: (225/250)
Solenoid Plate (50 parts) Solenoid Plate
Ref OEM Part # Part Name
- 84-881262A2 HARNESS ASSEMBLY, Alternator, Alternator
1 858366T2 PLATE
2 89-817109A2 SOLENOID ASSEMBLY, (#10-32 / .3125-18 Terminals)
3 25-822179 GROMMET
4 12-8M0204649 WASHER, (.281 x .500 x .060) Stainless Steel
5 10-82129125 SCREW, (M6 x 25 MM)
6 23-8M0214955 BUSHING
7 8M0207773 RELAY ASSEMBLY
8 NSS NOT SOLD SEPARATE, Decal-Trim Relay
9 828102 BRACKET
10 23-8M0214955 BUSHING
11 25-818967 GROMMET
12 10-82129110 SCREW, (M6 x 10)
13 54-816311T TIE STRAP, (8.00 Inches)
14 54-828991T CLIP
15 54-858755 CLIP, (1.00)
16 84-878231A6 HARNESS ASSEMBLY, Fuse - 100 Ampere
17 84-819514T21 HARNESS ASSEMBLY, Trim
18 84-892973T01 HARNESS ASSEMBLY, Engine
19 88-832969T05 FUSE, Mini - Tan - 5 Ampere Comment: (5 AMP)
20 858754 COVER, Fuse
21 84-882829A1 CABLE ASSEMBLY, Starter
22 84-88439A46 CABLE ASSEMBLY, Battery - Positive
23 11-8M0204668 NUT, (.312-18)
24 13-53166 LOCKWASHER, (.312)
25 10-32,11-813938 CAP NUT,
26 10-32,11-45076 NUT, Brass
27 84-88807A16 CABLE ASSEMBLY, (4.00 Inches) Black
28 13541 PLUG, Male
29 89790646T PCM, Propulsion Control Module Comment: (250)
30 10-82130025 SCREW, (M6 x 25)
31 12-65567 WASHER, (.265 x .750 x .048) Stainless Steel
32 25-8M0190980 GROMMET
33 23-856954 BUSHING
34 54-891520001 CLIP
35 10-82129114 SCREW, (M6 x 14)
36 892295F01 BRACKET
37 25-8M0190980 GROMMET
38 23-822003 BUSHING
39 881879T11 SENSOR, Pressure (0 - 100 PSI)
40 22-8M0207782 FITTING
41 54-883066 CLIP, (.865)
42 54-879962 CLIP
43 10-82130025 SCREW, (M6 x 25)
44 10-82130012 SCREW, (M6 x 12)
45 84-88439A26 CABLE ASSEMBLY, Battery - Negative
46 10-81893420 SCREW, (M8 x 20)
47 84-882815A1 HARNESS ASSEMBLY (200/3.0L Work)
48 877613A02 CONNECTOR ASSEMBLY, Weather Cap 6 Pin
49 830796A04 CONNECTOR ASSEMBLY, Weather Cap - Male
Speedometer/Block Pressure System (8 parts) Speedometer/Block Pressure System
Ref OEM Part # Part Name
1 22-881866 FITTING
2 32-85978571 TUBING, (52.00 Inches Bulk) (Cut to 44 Inches)
3 22-8M0214971 COUPLER
4 22-859732 PLUG
5 22-8M0214970 FITTING, Adapter
6 32-85978571 TUBING, (52.00 Inches Bulk) (Cut to 5 Inches)
7 22-875207 TEE, Fitting, To Coil Plate Sensor
8 32-85944975 TUBING, (72.00 Inches Bulk) (Cut to 52 Inches)
Starboard Bleed System (8 parts) Starboard Bleed System
Ref OEM Part # Part Name
- 883894A07 POWERHEAD ASSEMBLY Comment: (250)
1 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 15-1/2 Inches)
2 21-8592352 CHECK VALVE, 90 Degree (.0625-27)
3 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 16-1/2 Inches)
4 32-8M0054152 TUBING, (38.00 Inches Bulk) (Cut to 15 Inches)
5 54-23567 CLIP
6 10-878608 SCREW, (#10-16 x .500)
7 21-8282182 CHECK VALVE
Starter Motor (14 parts) Starter Motor
Ref OEM Part # Part Name
1 50-892339T01 STARTER MOTOR ASSEMBLY
2 NSS NOT SOLD SEPARATE, Thru Bolt
3 43-880805A1 GEAR KIT
4 809463A1 SOLENOID KIT
5 8M0065258 BRUSH SET
6 10-69035 SCREW AND LOCKWASHER, (.250-20 x .625) Stainless Steel
7 84-93388A1 CABLE ASSEMBLY, (6.00 Inches) Black
8 37-8272822 DECAL, Warning
9 13-400255 LOCKWASHER, (M5)
10 11-400211 NUT, (M5) Stainless Steel
11 13-8M0204647 LOCKWASHER, (.312)
12 11-400213 NUT, (M8) Stainless Steel
13 23-8M0034918 COLLAR
14 8M0043276 STOP
Swivel Bracket and Steering Arm (32 parts) Swivel Bracket and Steering Arm
Ref OEM Part # Part Name
1 1499-8M0102865 SWIVEL BRACKET ASSEMBLY, Black
2 25-8M0214926 O-RING
3 23-818764 BUSHING
4 23-816039 SPACER
5 26-87735 SEAL, Oil (Lower)
6 22-8M0169589 FITTING, Grease
7 23-821207 BUSHING
8 12-816432 THRUST WASHER
9 826364T YOKE, Bottom
10 53-67684 RING, Retaining
11 8M0045383 STRIKER PLATE
12 13-58643 LOCKWASHER, (.375)
13 11-46335 NUT, (.375-24)
14 10-64014 SCREW, (.250-28 x .500)
15 NSS NOT SOLD SEPARATE, Decal-Serial Overlaminate
16 8M0074846 SENDER ASSEMBLY, Trim
17 10-852368 SCREW, (#10-24 x .750)
18 10,13-26996 LOCKWASHER, Stainless Steel
19 12-89302 WASHER, (.203 x .406 x .040)
20 17-8M0132731 SWIVEL PIN ASSEMBLY, Steering Arm - Stainless Steel
21 10-8M0141069 SCREW, (M12 x 190)
22 824998001 BUMPER
23 8163851 MOUNT, Upper
24 12-8154371 WASHER
25 12-815436 WASHER
26 11-896963 NUT, (M12)
27 8M0036783 CLAMP
28 10-81893435 SCREW, (M8 x 35)
29 92876A12 LINK ROD ASSEMBLY
30 10-849838 SCREW, (.375-24 x 1.250)
31 11-8M0204726 NUT, (.375-24) Brass
32 12-37828 WASHER, (.390 x .625 x .062) Stainless Steel
Throttle Linkage (25 parts) Throttle Linkage
Ref OEM Part # Part Name
1 8M0040987 LEVER
2 10-81893435 SCREW, (M8 x 35)
3 12-36042 WASHER
4 23-821113 BUSHING
5 10-40124 SCREW, (M6 x 55)
6 11-400212 NUT, (M6) Stainless Steel
7 42942 CAP
8 42927 INSERT
9 11-401386 NUT, (M6) Stainless Steel
10 23-8M0215006 BUSHING
11 8583541 LINK, To Cam
12 824010T05 BRACKET
13 824016 LATCH
14 10-42975 DRIVE SCREW
15 824015 CUP, Barrel Retainer
16 10-82155025 SCREW, (M8 x 25 MM) Stainless Steel
17 54-859172 CLAMP
18 10-82155025 SCREW, (M8 x 25 MM) Stainless Steel
19 8M0039052 BRACKET, Slide
20 87-8M0207794 SWITCH
21 54-816311T TIE STRAP, (8.00 Inches)
22 10-82470620 SCREW, (M3.5 x 20)
23 12-43430 WASHER
24 12-35459 WASHER
25 12-36001 WASHER
Tools (1 parts) Tools
Ref OEM Part # Part Name
0 91-881814A1 SEAL KIT, Wire Harness (Electricl)
Top Cowl (24 parts) Top Cowl
Ref OEM Part # Part Name
- 37-809168A03 DECAL SET Comment: (Mariner 250)
1 4001-880012T36 TOP COWL ASSEMBLY, Silver Comment: SN# 1B447000 & Up
2 10-82130030 SCREW, (M6 x 30)
3 880014A02 SOUND BLANKET KIT
4 NSS NOT SOLD SEPARATE, Sound Blanket-Top
5 NSS NOT SOLD SEPARATE, Sound Blanket-Port
6 13-93702 WASHER, (.250 External Star)
7 826639T COVER
8 8M0010389 BRACKET ASSEMBLY, Cowl Comment: SN# 1B447000 & Up
9 NSS NOT SOLD SEPARATE, Pin
10 53-8237951 RING, Retaining
11 8M0207770 ROLLER
12 25-850685T02 GROMMET
13 8M0036792 BRACKET, Front
14 10-82130020 SCREW, (M6 x 20)
15 815477 BUMPER, Latch
16 8155381 PIN, Roll
17 11-401366 NUT, (M6) Stainless Steel
18 12-8M0204649 WASHER, (.281 x .500 x .060) Stainless Steel
19 53-8237951 RING, Retaining
20 8M0207770 ROLLER
21 12-87161 WASHER
22 NSS NOT SOLD SEPARATE, Decal-Break-In
23 NSS NOT SOLD SEPARATE, Decal-Counter Rotation
Transom Brackets (20 parts) Transom Brackets
Ref OEM Part # Part Name
1 3426-828334T03 BRACKET ASSEMBLY, Transom-Starboard
2 3425-828333T08 BRACKET ASSEMBLY, Transom-Port
3 22-8M0169588 FITTING, Grease, Port
4 826125A1 TILT TUBE
5 11-826135 NUT, (1.00-14) Nylon Insert
6 25-45711 O-RING, (.612 x .103)
7 13-88750 WASHER
8 11-826164 NUT, (.875-14)
9 10-8M0204730 SCREW, (.500-20 x 5 Inches)
10 12-8M0204665 WASHER, (.530 x .870 x .105) Stainless Steel
11 12-8M0204648 WASHER, (1.5 x 3.05 x 0.13) Stainless Steel
12 11-82671117 NUT, (.500-20)
13 8M0115104 LEVER ASSEMBLY, Tilt Lock
14 24-830899 SPRING, Tension
15 23-65830 NYLINER
16 24-830900 SPRING, Compression
17 99633 KNOB
18 17-99615 PIN, Groove
19 17-893709 PIN
20 37-8M0043059 DECAL, Warning
Vapor Separator Components (35 parts) Vapor Separator Components
Ref OEM Part # Part Name
1 883245T04 COVER KIT, Vapor Separator
2 22-881740 FITTING, Straight
3 22-883249 FITTING
4 NSS NOT SOLD SEPARATE, Elbow
5 22-885186A1 FITTING KIT
6 25-831985 O-RING, (.468 x .078)
7 35-885188 FILTER
8 883219 VALVE
9 25-8M0062785 O-RING
10 883220 CAP
11 19-883208 PLUG
12 26-883248 SEAL
13 27-883252 GASKET
14 883257T1 REGULATOR
15 25-883593A1 O-RING KIT
16 12-883258 WASHER
17 10-883261 SCREW, (M5 x .8)
18 10-883261 SCREW, (M5 x .8)
19 84-881831 WIRE ASSEMBLY
20 1395-808612 SCREW AND WASHER, (#8-32 x .750)
21 883253A1 FLOAT KIT
22 F10064 SHAFT
23 883247A1 VALVE/SEAT KIT, Inlet
24 10-883223 SCREW, (M6 x 16)
25 35-18458Q4 FILTER KIT
26 8M0204710 PROBE
27 889318002 BAFFLE
28 10-883223 SCREW, (M6 x 16)
29 881705T1 PUMP KIT
30 8M6000589 SLEEVE
31 883256T1 BOWL KIT
32 26-883248 SEAL
33 19-855435A1 PLUG KIT
34 25-8M0062785 O-RING
35 10-16955 SCREW, (M6 x 8)

100-Hour / Annual Service Checklist

Regular maintenance keeps your Mercury 250 (3.0L EFI) running reliably season after season. Most of these tasks can be performed with basic tools and the factory service manual.

  1. Replace water pump impeller and inspect wear plate
  2. Change engine oil and oil filter (check drain plug washer)
  3. Replace spark plugs and check ignition timing
  4. Drain and refill lower unit gear oil; inspect for water contamination
  5. Inspect fuel lines, primer bulb, and fuel filter for deterioration
  6. Check and replace sacrificial anodes (zinc or aluminum)
  7. Inspect propeller for damage; check shaft seal and cotter pin
  8. Check valve clearance (refer to service manual for specifications)
  9. Lubricate all grease points (steering, tilt tube, shift linkage)
  10. 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.

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