Tohatsu M50D Specifications
| Engine Model: Tohatsu M50D |
| 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 5500 rpm |
| Fuel System: Carburetor |
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The Tohatsu M50D is a three-cylinder,
loop-charged two-stroke outboard delivering 50 horsepower. Available in
several configurations - including electric start with tiller (DEFTO),
remote electric start with manual tilt (DEPO), and remote electric start
with power trim and tilt (DEPTO) - this engine is engineered for
reliability and ease of use. It is recognized for its strong
power-to-weight ratio and straightforward design, making it a popular
choice for boaters seeking a durable and efficient powerplant for a
range of small to medium-sized vessels.
The Tohatsu M50D represents a well-engineered and dependable outboard
option. Its in-line three-cylinder design provides smooth operation with
good fuel economy, a direct benefit of its loop-charged induction
system. The engine is built with corrosion-resistant materials,
including high-grade marine aluminum alloy and zinc-coated internal
water passages, enhancing its longevity, especially in saltwater
environments. An Electronic Safety Governor protects the engine from
over-revving by limiting RPM, while an overheat warning and water
pressure sensor provide additional operational security. The
availability of automixing and power trim and tilt on select models adds
to its user-friendly nature.
Engine Model: Tohatsu M50DEFO, M50DEFTO, M50DEPO, M50DEPTO.
Engine Type: 2-Stroke.
Number of Cylinders: 3.
Bore x Stroke: 68 mm x 64 mm (2.58 in x 2.52 in).
Piston Displacement: 697 cc (42.53 cu in).
Power Output: 36.8 kW (50 HP).
Full Throttle Operating Range: 5000-5700 r/min.
Exhaust System: Through propeller hub exhaust.
Cooling System: Forced water cooling with thermostat control.
Starting System: Manual (DEFO model) / Electric starter motor (DEFTO,
DEPO, DEPTO models).
Ignition System: Breakerless pointless CDI (Capacitor Discharge
Ignition).
Spark Plug: NGK B8HS-10 or Champion L-78.
Spark Plug Gap: 1.0 mm (0.039 in).
Trim Position (M50DEFTO, M50DEPO): 6.
Trim Position (M50DEFTO, M50DEPTO): 5.
Gear Shift: Dog clutch (F-N-R).
Gear Reduction Ratio: 1.85 (24:13).
Fuel: Unleaded Regular Gasoline with an anti-knock index of 84 or
higher.
Fuel Tank Capacity: 22.6 L (6.0 US gal) Separate fuel tank.
Engine Oil: Genuine two-stroke engine oil or NMMA certified TC-W3
outboard oil.
Engine Oil Capacity: 2.0 L (0.53 US gal).
Gear Oil: API GL-5, SAE 80-90.
Gear Oil Capacity: 0.5 L (16.9 US fl oz / 17.6 Imp fl oz).
PTT Fluid (DEPTO): ATF (Automatic Transmission Fluid) Dexron III.
The M50D features a loop-charged, three-cylinder powerhead. Loop
charging is a highly efficient scavenging method that directs the
fuel-air mixture in a loop to push out exhaust gases, resulting in
smoother operation and improved fuel economy compared to older
cross-flow designs.
The engine utilizes a breakerless CDI ignition system for quick and
reliable starts. It is built with a high-grade marine aluminum alloy for
the block and other components, providing excellent corrosion resistance
and durability while keeping weight low. Internal water passages receive
a zinc coating for superior corrosion resistance.
The fuel system is carbureted and designed to run on unleaded gasoline
with an octane rating of 84 or higher. A separate 22.6-liter fuel tank
is provided with the outboard.
The lubrication system varies by model. The base model requires fuel
pre-mixed at a 50:1 ratio. Many electric start versions, such as the
DEPO and DEPTO, feature Tohatsu's automixing oil injection system for
optimum lubrication under varying loads, which simplifies refueling. For
these automixing models, a 2-liter engine oil tank is located
conveniently on top of the motor for easy refills.
Cooling is managed by a forced water system that is thermostatically
controlled to maintain a consistent engine temperature for optimal
performance and longevity. The system features a water pump with a
durable stainless steel housing for outstanding reliability.
An overheat warning (audible alarm) alerts the operator if the engine
approaches a critical temperature. A water pressure sensor is also
incorporated into the system.
| Mid Section and Lower Unit |
The M50D is fitted with a durable mid section and lower unit housing a
forward-neutral-reverse dog clutch. The gear reduction ratio is 1.85:1
(24:13). The recommended gear oil is an API GL-5, SAE 80-90 grade, with
a total capacity of 0.5 liters.
The lower unit is equipped with a replaceable trim tab, which also
serves as a sacrificial anode for corrosion protection. The through-hub
exhaust system contributes to quieter operation.
The M50D is offered with two types of trim systems. The DEFO and DEPO
models feature a manual trim and tilt system. The DEFTO and DEPTO models
are equipped with a power trim and tilt system, which uses electric
hydraulic pumps to adjust the motor's angle.
This system uses Dexron III Automatic Transmission Fluid and has a
manual relief valve for emergency operation. The trim systems offer 5 or
6 trim positions depending on the model.
The recommended propeller selection range for the M50D is from 7 to 15
inches of pitch. The correct propeller must be selected so that the
engine operates within its wide-open throttle (WOT) range of 5000-5700
r/min under a normal load for optimal performance and engine longevity.
Overall Length (DEFO, DEFTO): 1107 mm (43.6 in)
Overall Length (DEPO, DEPTO): 630 mm (24.8 in)
Overall Width (DEFO, DEFTO): 381 mm (15.0 in)
Overall Width (DEPO): 340 mm (13.4 in)
Overall Width (DEPTO): 355 mm (14.0 in)
Overall Height (DEFO, DEFTO): 1352 mm (53.2 in)
Overall Height (DEPO, DEPTO): 1319 mm (51.9 in)
Transom Height (Short Shaft): 403 mm (15.9 in)
Transom Height (Long Shaft): 530 mm (20.9 in)
Transom Height (Ultra Long Shaft): 657 mm (25.9 in)
Weight (DEFO): 75 kg (166 lb)
Weight (DEFTO): 82 kg (181 lb)
Weight (DEPO): 70.5 kg (156 lb)
Weight (DEPTO): 77.5 kg (171 lb)
First 20 Hours / 1 Month: Initial dealer inspection. Every 50 Hours / 3
Months: Check and clean the fuel filter. Inspect spark plugs, clean or
replace as needed, and adjust gap to 1.0 mm (0.039 in). Check and
re-tighten all accessible bolts and nuts. Apply grease to all sliding
and rotating parts and grease nipples.
Every 100 Hours / 6 Months: Change gear oil, inspecting for water or
metal particles. Have a dealer check carburetor adjustment and ignition
timing. Inspect the water pump impeller for wear. Annually / Every 100
Hours: Replace the water pump impeller regardless of apparent condition.
General: Check anodes for corrosion and replace if significantly eroded.
Flush the cooling system with fresh water after each use in salt or
polluted water using the flushing attachment.
Gear Oil Plug: 4 Nm (3 lb-ft)
Propeller Nut: 35 Nm (25 lb-ft)
Spark Plug: 27 Nm (20 lb-ft)
PTT Manual Relief Valve: 1.8 Nm (1.4 lb-ft)
Fishing Boats: A popular choice for small aluminum tiller-steered boats,
jon boats, and lightweight center consoles. Utility Boats: Well-suited
for skiffs, inflatables, and other light commercial or recreational
utility craft used in sheltered waters. Auxiliary Power: Can serve as
reliable auxiliary power for larger sailing yachts.
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