Tohatsu M2.5/3.5A2/3.5B2 (2020) Parts & Diagrams

OEM and aftermarket replacement parts for Tohatsu M2.5/3.5A2/3.5B2. Scroll down for exploded parts diagrams (13), specifications, and maintenance reference.

Tohatsu M2.5/3.5A2/3.5B2 (2020) Parts & Diagrams

🔎 Tohatsu M2.5/3.5A2/3.5B2 Reference Library — Exploded parts diagrams (13 diagrams), specifications, common issues, and maintenance checklist.

The Tohatsu M2.5/3.5A2/3.5B2 is a 2-Stroke outboard motor. Designed for dinghies, inflatable boats, and small tenders where lightweight portability is essential.

Quick Reference Specifications

Specification Value
Engine Type 2-Stroke
Horsepower 2 HP
Displacement 74.6
Bore x Stroke 47 x 43
Spark Plug (Type & Gap) NGK BPR6HS-10
Engine Oil Capacity
Recommended Engine Oil TC-W3 Certified 2-Stroke Oil
Gear Case Oil Capacity 90 mL
Idle Speed (in gear) 1100
Full Throttle RPM Range 4200-5300
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 Tohatsu M2.5/3.5A2/3.5B2:

  • 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
  • Fuel System Issues / Hard Starting: Stale fuel and ethanol-related deposits are common in 2-stroke carbureted engines. Clean or rebuild carburetors and replace fuel lines if deteriorated. → Recommended: Carburetor Repair Kit, Fuel Line Assembly
  • Spark Plug Fouling: 2-stroke engines are prone to spark plug fouling from oil residue, especially at low RPM. Replace plugs at each annual service. → Recommended: OEM Spark Plugs
  • 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
  • Thermostat Failure: A stuck thermostat can cause overheating or poor warm-up. Replace if operating temperature is inconsistent. → Recommended: Thermostat Assembly

Parts Diagrams & OEM Part Numbers

Expand the sections below to view detailed exploded parts diagrams and find the exact OEM replacement components for your Tohatsu M2.5/3.5A2/3.5B2.

Fig.01 CYLINDER・CRANK CASE (20 parts) Fig.01 CYLINDER・CRANK CASE
Ref OEM Part # Part Name
1 3F0B01100-1 CYL BLOCK & CRANKCASE ASSY
2 393-01131-0 * NIPPLE 5.5-5
3 345-01111-0 * DOWEL PIN 6-12
4 916124-0665 * BOLT
5 910124-0630 * BOLT
6 309B01001-2 CYLINDER HEAD
7 309-01005-2 CYLINDER HEAD GASKET
8 9161F4-0630 BOLT
9 940121-0600 WASHER
10 309-02111-0 REED VALVE
11 309-02113-0 REED VALVE STOPPER
12 921521-7412 SCREW
13 9701-1-1013 SPARK PLUG(BPR6HS-10)
14 98AB-30-150 HOSE
15 3F0-01214-0 CRANKCASE HEAD GASKET
16 3F0-01210-1 CRANKCASE HEAD
17 3F0-01215-0 OIL SEAL 10.1-20-7
18 309-01210-1 CRANKCASE HEAD
19 910103-5618 BOLT
20 3PR-06972-0 CLAMP 6.5-47.5P
Fig.02 PISTON・CRANK SHAFT (21 parts) Fig.02 PISTON・CRANK SHAFT
Ref OEM Part # Part Name
1 309-00106-0 THRUST PLATE
2 3F0-00107-0 THRUST PLATE
3 309-00121-0 OIL SEAL 20-42-8
4 309-00122-0 OIL SEAL 15-35-15
5 3F0-00122-0 OIL SEAL 17-40-8
6 309-00069-0 CRANKSHAFT SUB-ASSY
7 3F0-00069-0 CRANKSHAFT SUB-ASSY
8 309-00040-0 * CONNECTING ROD
9 309-00043-0 * ROLLER BEARING 16-22-12
10 309-00031-0 * CRANKSHAFT A
11 309-00034-0 * CRANKSHAFT D
12 3F0-00034-0 * CRANKSHAFT D
13 309-00061-1 * CRANK PIN
14 3F0-00113-0 MAIN BEARING 6004
15 9643-3-6203 BALL BEARING 6203
16 309-00042-0 ROLLER BEARING 10.5-14-15
17 302-00014-0 PISTON RING (0.5 O/S)
18 309-87131-0 PISTON REPAIR KIT (0.5 O/S)
19 309-00004-1 * PISTON (0.5 O/S)
20 309-00021-1 * PISTON PIN
21 309-00024-1 * PISTON PIN CLIP
Fig.03 CARBURETOR (42 parts) Fig.03 CARBURETOR
Ref OEM Part # Part Name
1 3F0-03100-5 CARBURETOR ASSY
2 309-03170-0 * THROTTLE WIRE ASSY
3 309-03178-0 * SCREW
4 309-03173-0 * THROTTLE LEVER HOLDER
5 309-03101-0 * CARBURETOR BODY CAP
6 309-03107-0 * THROTTLE VALVE SPRING
7 309-03108-0 * SPRING RECEIVER
8 309-03154-0 * JET NEEDLE CLIP
9 3F0-03153-3 * JET NEEDLE (#256)
10 3D5-03106-0 * THROTTLE VALVE
11 309-03155-2 * NEEDLE JET
12 309-03121-0 * FLOAT CHAMBER GASKET
13 309-03125-0 * FLOAT
14 309-03120-0 * FLOAT CHAMBER
15 309-03192-0 * DRAIN SCREW
16 309-03193-0 * GASKET
17 309-03151-3 * MAIN JET (#86)
18 309-03126-0 * FLOAT ARM PIN
19 309-03127-1 * FLOAT HINGE
20 309-03147-1 * FLOAT VALVE
21 3D7-03148-0 * NEEDLE VALVE SEAT L=27
22 309-03156-0 * ADJUST SCREW
23 309-03157-0 * SPRING
24 309-03161-0 * CHOKE PLATE
25 332-03104-0 * CHOKE PLATE NUT
26 941303-0600 * SPRING WASHER
27 309-03163-0 * SHUTTER BOLT
28 309-03164-0 * SHUTTER LEVER
29 309-03113-0 * CARBURETOR BODY BAND
30 309-03114-0 * CARBURETOR BODY BAND BOLT
31 921532-6410 * SCREW
32 921532-0510 * SCREW
33 309-03177-0 * THROTTLE LEVER WASHER
34 309-03175-0 * THROTTLE LEVER GASKET
35 309-03176-1 * THROTTLE LEVER END
36 309-03174-1 * THROTTLE LEVER COLLAR
37 309-03172-1 * THROTTLE LEVER
38 309-03116-2 * O-RING 2.4-15.7
39 309-03401-0 KNOB
40 921603-0305 SCREW
41 3F0B02496-3 CARBURETOR COVER W/DECAL
42 921603-0435 SCREW
Fig.04 RECOIL STARTER (18 parts) Fig.04 RECOIL STARTER
Ref OEM Part # Part Name
1 312-05000-0 RECOIL STARTER ASSY
2 312-05001-0 * STARTER CASE
3 307-05004-0 * STARTER SPRING
4 307-05104-0 * REEL
5 307-05003-0 * RATCHET
6 307-05007-0 * FRICTION SPRING
7 307-05021-0 * SPRING COVER
8 307-05012-0 * RETURN SPRING
9 307-05006-0 * FRICTION PLATE
10 307-05027-0 * THRUST WASHER
11 307-05011-0 * E-RING
12 307-05013-0 * STARTER ROPE φ4-1250
13 307-05019-0 * STARTER HANDLE
14 309-05028-0 * PAD
16 910121-0612 BOLT
17 309-05901-1 STARTER PULLEY
18 3F0-72185-0 CAUTION DECAL
19 314-72185-0 CAUTION DECAL
Fig.05 MAGNETO (18 parts) Fig.05 MAGNETO
Ref OEM Part # Part Name
1 3F0-06101-0 FLYWHEEL ASSY
2 3F0-06120-0 EXCITER COIL
3 3F0-06915-0 CLAMP
4 309-00132-0 NUT 10-P1.25
5 921521-6520 SCREW
6 921521-0510 SCREW
7 369-06050-3 IGNITION COIL W/CAP
9 3F0-06157-0 * PROTECTOR
10 3M2-06926-0 * PLUG CAP TERMINAL
11 3M2-06921-0 * PLUG CAP
12 910103-0620 BOLT
13 3F0-06060-0 CD UNIT
14 910103-0616 BOLT
15 3C8-66308-0 WASHER 6-16-1.5
16 309-00131-0 KEY 10-3.7-3
17 3D5-06870-0 STOP SWITCH ASSY
18 353-06821-0 * STOP SWITCH LANYARD ASSY
19 3C7-06921-0 PLUG CAP W/RESISTANCE
Fig.06 DRIVE SHAFT HOUSING・TILLER HANDLE (M3.5B2) (37 parts) Fig.06 DRIVE SHAFT HOUSING・TILLER HANDLE (M3.5B2)
Ref OEM Part # Part Name
1 9101E3-7635 BOLT
2 3F0Q61020-2 DRIVE SHAFT HOUSING (S)
3 345-01111-0 DOWEL PIN 6-12
4 9101E3-5625 BOLT
5 309-61012-3 DRIVE SHAFT HOUSING GASKET
6 9106E3-0808 BOLT
7 332-60006-1 GASKET
8 369-61016-0 GROMMET 29-3
9 3F0Q61102-2 EXTENSION HOUSING ASSY (L)
10 369-60003-0 * DRIVE SHAFT BUSHING
11 3F0-61101-1 STUD 6-171
13 3F0-66214-0 SHIFT ROD (S)
14 951503-0212 SPLIT PIN 2-12
15 940103-0500 WASHER
16 369-66241-0 SHIFT ROD JOINT ASSY
17 910103-5616 BOLT
18 3F0-66110-0 SHIFT LEVER
19 3G9-66136-0 O-RING 2-10
20 369-66116-0 CERAMIC BALL 7.7
21 369-66112-1 SPRING
22 3F0-66225-0 SHIFT ROD LEVER
23 3F0-66227-0 TAPPING SCREW 4-20
24 940103-0400 WASHER
25 3F0Q66228-0 COVER
26 9101E3-0616 BOLT
28 3F0-66229-1 GASKET
29 309Q63010-0 TILLER HANDLE ASSY
30 309Q63011-0 * TILLER HANDLE
31 309-63012-0 * GRIP
32 910103-0830 BOLT
33 309-63024-0 TILLER HANDLE DAMPER
34 309-63025-0 SPACER 8.4-12-14.2
35 345-67115-0 WASHER 6.5-21-1
36 3F0Q67521-0 CARRYING HANDLE
37 9101E3-0625 BOLT
38 9301E3-0600 NUT
39 3GR-76191-0 HIGH TEMPERATURE CAUTION DECAL
Fig.07 GEAR CASE (M3.5B2) (48 parts) Fig.07 GEAR CASE (M3.5B2)
Ref OEM Part # Part Name
1 3ARQ60000-1 GEAR CASE ASSY
3 338-60218-2 * ANODE
4 910103-0616 * BOLT
5 9601-0-6004 BALL BEARING 6004
6 332-60005-2 PLUG 8-8
7 332-60006-1 GASKET
8 3F0-64321-0 SPACER 10.1-15-72
9 3F0Q87323-1 PROPELLER SHAFT HOUSING ASSY
10 3F0Q60101-1 * PROPELLER SHAFT HOUSING
11 9601-0-6001 * BALL BEARING 6001
12 309-60111-0 * OIL SEAL 12-24-8
13 345-65015-0 * O-RING 3.2-47
14 3GR-64010-0 BEVEL GEAR ASSY (A)
15 369-64015-0 SHIM 21-28-0.15
16 3GR-64020-0 BEVEL GEAR B
17 3F0-64302-0 DRIVE SHAFT ASSY (L)
18 9601-0-6000 * BALL BEARING 6000
19 369-65021-1 WATER PUMP IMPELLER
20 369-65022-0 KEY φ2-11
21 3F0-65016-0 PUMP CASE (UPPER)
22 3F0-65011-0 PUMP CASE LINER
23 3F0-65032-0 GROMMET
24 3F0-65018-0 PUMP CASE GASKET
25 3F0-65025-0 WATER PUMP GUIDE PLATE
26 3F0-65029-0 GUIDE PLATE GASKET
27 9161E3-0645 BOLT
28 940103-0600 WASHER
30 3H2-65040-1 PUMP CASE ASSY (LOWER)
31 3F0-60223-0 * OIL SEAL 10-22-8
32 3F0-65020-0 PUMP CASE GASKET (LOWER)
33 301-66023-0 O-RING 2.4-9.5
34 3B2-65022-0 KEY φ3-11
35 3F0-66031-0 CAM ROD BUSHING
36 3F0-64215-0 CLUTCH
37 3F0-64221-0 SPRING
38 3F0-64223-0 PUSH ROD
39 3F0-64211-0 PROPELLER SHAFT
40 3F0-66011-0 CLUTCH CAM
41 3F0-66013-0 CAM ROD (L)
42 951407-0308 SPRING PIN 3-8
43 369-66021-1 O-RING 2.5-4.9
44 9101E3-7635 BOLT
45 9101E3-5620 BOLT
46 951503-0435 SPLIT PIN 4-35
47 309-64126-1 SHEAR PIN 4-24
48 3F0-65110-0 WATER PIPE ASSY (L)
49 309-65031-1 * GROMMET 10.6-10.4-4
50 3F0B64512-0 PROPELLER ASSY (6")
Fig.08 DRIVE SHAFT HOUSING・GEAR CASE (M2.5/3.5A2) (24 parts) Fig.08 DRIVE SHAFT HOUSING・GEAR CASE (M2.5/3.5A2)
Ref OEM Part # Part Name
1 309Q60000-2 GEAR CASE ASSY
2 309-64321-1 * SPACER
4 945002-2800 * C-RING d=28
5 309-64311-1 DRIVE SHAFT (LOWER)
6 9601-0-6300 BALL BEARING 6300
7 309-64017-0 SHIM 17.5-10.2-0.05
8 309-64020-0 BEVEL GEAR B
9 945307-0700 E-RING d=7
10 309-65021-1 WATER PUMP IMPELLER
11 309-65022-0 KEY φ4-15
12 309Q65010-1 WATER PUMP CASE
13 9601-0-6001 BALL BEARING 6001
14 309-60111-0 OIL SEAL 12-24-8
15 309-65015-0 O-RING 1.5-47.75
16 309-65032-0 GROMMET 10.2-8
17 309-64210-0 PROPELLER SHAFT ASSY
18 9101E3-7630 BOLT
19 309-60223-0 OIL SEAL 13-28.1-18
20 309Q60101-1 WATER PUMP CASE COVER
21 309Q61030-2 DRIVE SHAFT HOUSING (L)
22 309-64313-1 DRIVE SHAFT (UPPER L)
23 309-64323-0 GIRD PIPE
24 309-65110-0 WATER PIPE ASSY (L)
25 309Q67521-0 CARRYING HANDLE
Fig.09 CLAMP BRACKET・SWIVEL BRACKET (25 parts) Fig.09 CLAMP BRACKET・SWIVEL BRACKET
Ref OEM Part # Part Name
1 309Q62111-4 CLAMP BRACKET
2 309-62115-2 BOLT 8-122
3 930403-0800 NYLON NUT 8-P1.25
4 307-62116-1 WASHER 8.5-28-1
5 309-62117-1 DISTANCE PIECE
6 930103-0600 NUT
8 309-62212-2 THRUST SUPPORTER
9 3F0-62160-0 THRUST ROD ASSY
10 309-62463-0 KNOB
11 309-62464-2 TILT STOPPER
12 309Q62391-1 SWIVEL BRACKET
13 309Q62392-1 SWIVEL BRACKET
14 9101E3-0630 BOLT
15 309-62321-1 BUSHING
16 3GT-62442-0 FRICTION KNOB
17 309-62441-2 FRICTION PIECE
18 309-62446-1 SPRING
19 9401E3-0600 WASHER
20 3GTQ62105-1 CLAMP SCREW KIT
21 3GTQ62108-1 * CLAMP SCREW ASSY
22 369-62106-1 ** CLAMP SCREW
23 3ABQ62102-0 ** CLAMP SCREW HANDLE
24 3C8-62104-2 ** RIVET 3-22
25 332-62101-1 * CLAMP SCREW PAD
26 3C8-62107-0 * SHOULDER BOLT
Fig.10 TOP COWL (10 parts) Fig.10 TOP COWL
Ref OEM Part # Part Name
1 3F0-87803-0 DECAL SET (M3.5B2) (M3.5B2)
2 9215E3-0612 SCREW
3 309-67006-0 TOP COWL JOINT PLATE
4 309-67007-0 NUT
5 921603-0510 SCREW
6 309Q06927-1 COVER
7 307-67005-0 GROMMET 16-5-2.5
9 3F0Q67001-9 TOP COWL SUB-ASSY (R)
10 309Q67002-9 TOP COWL SUB-ASSY (L)
11 314-67538-0 * SIMPLIQ DECAL
Fig.11 FUEL TANK (15 parts) Fig.11 FUEL TANK
Ref OEM Part # Part Name
1 3GP-70020-0 FUEL TANK CAP ASSY
2 3GR-70021-0 * TANK FILLER CAP GASKET
3 940103-0400 * WASHER
4 3H9-70095-0 * HOOK
5 951503-1610 * SPLIT PIN 1.6-10
6 309-70010-3 FUEL TANK
7 309-70015-0 SPACER 7.2-10-6
8 309-70016-0 WASHER 6.5-16-2
9 910421-0620 BOLT
10 941322-0600 SPRING WASHER
11 309-70011-0 FUEL COCK ASSY
12 309-70315-0 FUEL HOSE
13 3GT-35143-0 CLIP φ9.4
14 309-70036-0 FUEL TANK SEAL
15 309-06157-0 PROTECTOR L=220
Fig.12 OPTIONAL PARTS (ACCESSORIES) (3 parts) Fig.12 OPTIONAL PARTS (ACCESSORIES)
Ref OEM Part # Part Name
1 312-72201-0 SAFETY ROPE φ4-1000
2 312-72100-0 TOOL KIT
3 336-60007-0 FLUSHING PLUG
Fig.13 ASSEMBLY・KIT PARTS (8 parts) Fig.13 ASSEMBLY・KIT PARTS
Ref OEM Part # Part Name
1 3ARQ87302-2 LOWER UNIT ASSY (L)
2 309Q87301-1 LOWER UNIT ASSY (S)
3 3F0B87090-5 ENGINE SHORT BLOCK KIT
4 921532-6410 * SCREW
5 3F0-87121-3 POWER HEAD GASKET SET
6 940103-0600 * WASHER
7 3F0-87321-0 LOWER UNIT GASKET SET
8 951407-0308 * SPRING PIN 3-8

100-Hour / Annual Service Checklist

Regular maintenance keeps your Tohatsu M2.5/3.5A2/3.5B2 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. Inspect and clean carburetor(s); check fuel mixture settings
  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. Decarbonize exhaust ports and piston crown if needed
  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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