Tohatsu M5B Specifications
| Engine Model: Tohatsu M5B |
| Engine Type: 2-stroke 1-cylinder gasoline outboard engine |
| Total Displacement: 6.2 cu.in (102 cc) |
| Rated Engine Power: 5 Hp (3.7 kW) at 5500 rpm |
| Fuel System: Carburetor |
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The Tohatsu M5B is a technologically
uncomplicated yet highly effective outboard that distinguishes itself
through its lightweight and portable design, offering boaters an
incredible power-to-weight ratio. Its engineering focus is on
reliability and user convenience, highlighted by the loop-charged
induction system for smooth operation and fuel economy, and a CD
ignition system for quick and easy starts.
Users benefit from a simple tiller control with forward, neutral, and
reverse gears, along with a shallow water drive for navigating in low
waters. The engine is engineered for durability in marine environments,
incorporating high-grade marine aluminum alloy and zinc coating on
internal water passages for superior corrosion resistance, making it a
reliable and clean-operating powerplant for small boat applications. It
is also sold under the Mariner and Mercury 5 branding, ensuring
widespread parts availability.
Engine Model: Tohatsu M5B (variants include M5BD and M5BS)
Engine Type: 2-stroke, single-cylinder, gasoline outboard engine
Number of Cylinders: 1
Displacement: 6.22 cu in (102 cc)
Cylinder Bore: 2.17 in (55.0 mm)
Piston Stroke: 1.69 in (43.0 mm)
Maximum Engine Power: 5.0 hp (3.7 kW)
Maximum Engine Speed: 4500-5500 rpm
Idle Speed: 850-1000 rpm
Lubrication System: Pre-mixed fuel and oil
Exhaust System: Through propeller hub
Cooling System: Water-cooled
Ignition System: Flywheel magneto CDI with electronic timing advance
Starting System: Manual recoil starter
Alternator Output: Optional: 12V, 60W, 5A
Cylinder Bore Inside Diameter: 2.165-2.166 in (55.00-55.01 mm)
Piston to Cylinder Clearance: 0.0012-0.0024 in (0.03-0.06 mm)
Top Ring End Gap: 0.008-0.016 in (0.20-0.40 mm)
Second Ring End Gap: 0.008-0.016 in (0.20-0.40 mm)
Top Ring Side Clearance: 0.0011-0.0028 in (0.03-0.07 mm)
Second Ring Side Clearance: 0.0008-0.0024 in (0.02-0.06 mm)
Piston to Piston Pin Clearance: 0.0002-0.0031 in (0.01-0.08 mm)
Connecting Rod Big End Side Clearance: 0.0051-0.0146 in (0.13-0.37 mm)
Fuel System Type: Carburetor (Keihin Seiki BCK 21-15)
Fuel Type: Unleaded gasoline, 87 octane minimum
Fuel Consumption: 1.6 L/hr at maximum speed
Fuel Tank Capacity (Integral): 2.5 L (0.66 US gal)
Fuel Tank Capacity (Separate, M5BS): 12.0 L (3.17 US gal)
System Type: Pre-mix (fuel/oil ratio 50:1 for normal operation)
Engine Oil Type: Genuine two-stroke outboard oil, NMMA TCW-III certified
Engine Oil and Fuel Ratio: 50 parts unleaded gasoline to 1 part
two-stroke engine oil.
For initial break-in of a new engine, a 25:1 ratio is recommended for
the first 10 hours.
System Type: Water cooling
Water Pump: Driven by driveshaft, with rubber impeller.
Recommended replacement interval is every 100-200 hours.
Thermostat: Not equipped; engine runs cold at low speeds.
| Mid Section and Lower Unit |
Mid Section: Integral driveshaft housing
Steering System (Std): Tiller handle with 360-degree steering
Steering System (Opt): Remote control
Shift System: Dog clutch
Gear Shift: Forward - Neutral - Reverse
Reverse Lock: Automatically engages when reverse is selected
Gear Ratio: 2.15:1 (13:28)
Gearcase Capacity: 0.20 qts (0.19 L)
Gear Lubricant Type: Genuine Tohatsu gear oil or API GL-5, SAE 80, SAE
90
Trim System: Manual Trim and Tilt
Trim Positions: 6 positions
Shallow Water Drive: Standard, with approximately 40-degree tilt setting
Maximum Tilt Angle: 75 degrees
Propeller Types: 3-blade, aluminum
Propeller Diameter Range: 7.8 in (198 mm) to 7.9 in (200 mm)
Propeller Pitch Range: 6 in (152 mm) to 9 in (229 mm)
Standard Propeller: 8-inch pitch alloy prop
Overall Length: 27.6 in (700 mm)
Overall Width: 12.2 in (310 mm)
Overall Height (Short Shaft model): 39.6 in (1005 mm)
Overall Height (Long Shaft model): 44.6 in (1135 mm)
Overall Height (M5BS, Short Shaft): 38.5 in (980 mm)
Overall Height (M5BS, Long Shaft): 43.5 in (1105 mm)
Transom Height (Short Shaft): 15 in (381 mm)
Transom Height (Long Shaft): 20 in (508 mm)
Outboard Weight (Short Shaft): 44.0 lbs (20.0 kg)
Outboard Weight (M5BS, Short Shaft): 42.0 lbs (19.0 kg)
Outboard Weight (Long Shaft): 45.0 lbs (19.5 kg)
Outboard Weight (M5BS, Long Shaft): 43.0 lbs (20.5 kg)
Engine Fuel: Unleaded gasoline, 87 octane minimum
Engine Oil: NMMA TCW-III certified two-stroke oil
Fuel/Oil Ratio: 50:1 (normal); 25:1 (break-in period)
Gear Lubricant: API GL-5, SAE 80 to 90
Gearcase Capacity: 0.20 qts (0.19 L)
Ignition Timing: 20-30 degrees BTDC (electronically advanced)
Spark Plug Type: NGK BP7HS-10 or NGK BPR7HS-10
Spark Plug Gap: 0.035-0.039 in (0.9-1.0 mm)
Every 50 Hours or 6 months: Check
spark plug, check fuel line, clean fuel tank, check anodes, check gear
oil level, check propeller, check starter rope for wear.
Every 100 Hours: Check cooling
system operation, check water pump, check/adjust carburetor.
Every 200 Hours: Replace gear oil,
replace spark plug, replace water pump impeller.
Cylinder Head Bolt: 18.8 lb-ft (25.5 Nm)
Magneto Nut: 43.7 lb-ft (59 Nm)
Crankcase Bolt: 8.2 lb-ft (11 Nm)
Propeller Nut: 9.0 lb-ft (12 Nm)
Spark Plug: 20.0 lb-ft (27 Nm)
Mounting Bolts: 13.0 lb-ft (30 Nm)
Gear Oil Plug: 3.0 lb-ft (4 Nm)
The Tohatsu M5B is a versatile outboard ideally suited for a wide range
of small, portable watercraft up to approximately 3.4 meters in length.
Its light weight and compact dimensions make it an excellent choice for
powering aluminum tinnies, inflatable boats, dinghies, and small tenders
used as shore craft for larger vessels. It is also a popular powerplant
for small fishing boats, jon boats, and punts used on lakes and rivers,
where its portability allows for easy transport and storage.
The engine's straightforward design and reliable operation make it
well-matched for recreational boaters, anglers, and as an auxiliary
motor for sailboats, where efficiency and ease of use are paramount. The
M5B performs best on flat-bottomed hulls with relatively large planing
surfaces relative to the total load weight.
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