Tohatsu MD50B2 Specifications
| Engine Model: Tohatsu MD50B2 |
| Engine Type: 2-stroke 3-cylinder gasoline outboard engine |
| Total Displacement: 42.5 cu.in (697 cc) |
| Rated Engine Power: 50 Hp (36.8 kW) at 5850 rpm |
| Fuel System: Two stroke low pressure direct injection (TLDI) |
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The Tohatsu MD50B2 is a technologically
advanced outboard that distinguishes itself through its TLDI
air-assisted direct fuel injection system. Its engineering focus is on
delivering the high power-to-weight ratio of a traditional two-stroke
while eliminating the smoke, noise, and inefficiency associated with
older carbureted models. This system provides exceptional fuel economy,
extremely quiet operation, and ultra-low emissions, meeting stringent
EPA and CARB regulations.
Users benefit from a multi-point oil injection system that ensures
precise lubrication and eliminates the need for pre-mixing fuel, along
with a powerful 23-amp alternator for charging batteries. The engine is
engineered for durability, incorporating high-grade marine aluminum
alloy, a stainless steel water pump housing liner, and zinc coating on
internal water passages for superior corrosion resistance, making it a
reliable and powerful powerplant for a variety of mid-sized boats.
Engine Model: Tohatsu MD50B2 (various model codes: EPTOL, EFTOS, EFTOL)
Engine Type: 2-stroke, 3-cylinder, gasoline outboard engine with TLDI
Displacement: 42.5 cu in (697 cc)
Cylinder Bore: 2.68 in (68.0 mm)
Piston Stroke: 2.52 in (64.0 mm)
Maximum Engine Power: 50.0 hp (36.8 kW)
Maximum Engine Speed: 5150-5850 rpm
Firing Order: 1-2-3
Compression Ratio: 7.2:1
Idle Speed: 700, 800, or 900 rpm (user-selectable)
Trolling Speed: 800 rpm
Lubrication System: Multi-point automatic oil injection
Exhaust System: Through propeller hub
Cooling System: Water cooling with thermostat
Ignition System: Inductive
Starting System: Electric starter
Charging System: Alternator
Alternator Rating: 12V, 280W, 23A
Cylinder Bore Inside Diameter: 2.677-2.679 in (68.00-68.05 mm)
Piston to Cylinder Clearance: 0.0031-0.0047 in (0.08-0.12 mm)
Piston Skirt Diameter: 2.674-2.675 in (67.92-67.96 mm)
Piston to Piston Pin Clearance: 0.0002-0.0005 in (0.005-0.013 mm)
Piston Pin Bore Inside Diameter: 0.6693-0.6695 in (17.001-17.007 mm)
Top Ring End Gap: 0.015-0.021 in (0.38-0.53 mm)
Second Ring End Gap: 0.015-0.021 in (0.38-0.53 mm)
Top Ring Side Clearance: 0.0016-0.0032 in (0.04-0.08 mm)
Second Ring Side Clearance: 0.0016-0.0032 in (0.04-0.08 mm)
Fuel System Type: Two-stroke Low Pressure Direct Injection (TLDI) with
air-assisted direct fuel injection
Fuel Injection: Direct fuel injection into cylinders
Engine Control Unit: 32-bit ECU controls fuel injection and ignition
timing
Air Compressor: Essential component for achieving stabilized fuel
injection
Fuel Type: Unleaded gasoline, 87 octane minimum
Fuel Consumption: 16.5 L/hr
Fuel Tank Capacity: 6.6 gal (25.0 L) optional portable fuel tank
System Type: Automatic multi-point oil injection
Oil Reservoir Location: Top of the motor for easier refill onboard
Oil Pump: Electric oil pump ensures accurate oil metering
Engine Oil Type: Premium TCW-3 two-stroke outboard oil
Engine Oil Capacity: 2.1 qts (2.0 L) oil tank capacity
System Type: Water cooling with thermostat
Cooling System Sensor: Special sensor ensures optimal temperature
control
Water Pump: Driven by driveshaft, with rubber impeller
Water Pump Housing: Stainless steel liner for outstanding durability
Corrosion Protection: Zinc coating on internal water passages
Flushing: Fresh water flushing after use in salt or brackish water
recommended to maintain cooling passages
| Mid Section and Lower Unit |
Mid Section: Integral driveshaft housing with high-grade marine aluminum
alloy for corrosion protection
Steering System: Tiller handle or remote control
Tiller Handle Features: Multi-function tiller handle with gear shift,
throttle, trim switch, safety lanyard, warning lights, and electric
start key switch integrated
Steering Angle: 75 degrees
Shift System: Dog clutch
Gear Shift: Forward - Neutral - Reverse
Gear Type: Spiral bevel gear
Gear Ratio: 1.85:1
Gearcase Capacity: 0.53 qts (0.50 L)
Gear Lubricant Type: Hypoid gear oil or API GL-5, SAE 80 to 90
Trim System: Power Trim and Tilt (standard on most models)
Trim System (EFO models): Manual Trim and Tilt
Tilt Positions (Power Trim): 4 positions
Tilt Positions (Manual): 6 positions
Maximum Tilt Angle: 80 degrees
Propeller Types: 3-blade, aluminum (4-blade optional for some
applications)
Propeller Diameter Range: 10.9 in (278 mm) to 12.2 in (311 mm)
Propeller Pitch Range: 7 in (178 mm) to 15 in (381 mm)
Standard Propeller Pitches: 9, 11, 12, 13, 14, 15 inches
Propeller Selection Note: For light boat loads, select larger pitch; for
heavy loads, select smaller pitch to achieve recommended WOT rpm range
of 5,150-5,850
Overall Length: 44.1 in (1120 mm)
Overall Width: 15.1 in (385 mm)
Overall Height (Short Shaft model): 48.3 in (1225 mm)
Overall Height (Long Shaft model): 53.3 in (1355 mm)
Overall Height (Extra Long Shaft model): 58.3 in (1480 mm)
Transom Height (Short Shaft): 15 in (381 mm)
Transom Height (Long Shaft): 20 in (508 mm)
Transom Height (Extra Long Shaft): 25 in (635 mm)
Outboard Weight (Short Shaft): 205.7 lbs (93.5 kg)
Outboard Weight (Long Shaft): 205.7 lbs (93.5 kg)
Outboard Weight (Extra Long Shaft): 220 lbs (100.0 kg)
Engine Fuel: Unleaded gasoline, 87 octane minimum
Engine Oil: Premium TCW-3 two-stroke outboard oil
Gear Lubricant: Hypoid gear oil, API GL-5, SAE 80 to 90
Gearcase Capacity: 0.53 qts (0.50 L)
Ignition Timing: Electronically controlled by ECU
Spark Plug Type: NGK IZFR6J or NGK IZFR6Q
Spark Plug Gap: 0.031-0.035 in (0.8-0.9 mm)
Warning Systems: Overheat warning (visual and audible), low oil level
warning (visual and audible), battery voltage warning (visual only),
over-rev limiter
Safety Features: Start-in-gear protection, safety lanyard
Every 50 Hours: Check gear oil
level, check propeller for damage.
Every 100 Hours: Check battery,
check fuel filter, check spark plugs, check fuel line, check anodes,
check drive belt, check air filter, clean fuel tank, check cooling
system, check water pump, change gear oil.
Every 200 Hours: Replace
high-pressure fuel filter, replace fuel filter, replace spark plugs.
Cylinder Head Bolt: 23.0 lb-ft (32 Nm)
Crankcase Bolt: 18.0 lb-ft (25 Nm)
Exhaust Cover Bolt: 9.0 lb-ft (12 Nm)
Compressor Head Bolt: 7.0 lb-ft (9 Nm)
Air Box Bolt: 7.0 lb-ft (9 Nm)
Flywheel Nut: 108.0 lb-ft (150 Nm)
Drive Pulley Nut: 74.0 lb-ft (100 Nm)
Propeller Nut: 25.0 lb-ft (35 Nm)
Gear Case Bolt: 14.0 lb-ft (20 Nm)
Spark Plug: 18.0 lb-ft (25 Nm)
The Tohatsu MD50B2 is a versatile outboard ideally suited for a wide
range of mid-sized boats requiring a lightweight yet powerful propulsion
system. Its exceptional power-to-weight ratio (up to 15% lighter than
competitive four-strokes) makes it an excellent choice for powering
rigid inflatable boats (RIBs) up to approximately 4.5-5.0 meters,
providing exhilarating acceleration and planing performance. It is also
a popular powerplant for aluminum fishing boats, jon boats, and bay
boats where shallow water maneuvering is required.
Additionally, its compact dimensions and reliable operation make it
well-matched for small center console skiffs, pontoon boats, and as a
primary power source for light commercial vessels such as patrol boats
and tenders, where efficiency, durability, and ease of maintenance are
paramount. The availability of both tiller (EFTOS/EFTOL) and remote
control models broadens its adaptability, from simple, single-operator
craft to more sophisticated recreational and commercial applications.
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