Tohatsu MD30B2 Specifications
| Engine Model: Tohatsu MD30B2 |
| Engine Type: 2-stroke 3-cylinder gasoline outboard engine |
| Total Displacement: 42.5 cu.in (697 cc) |
| Rated Engine Power: 30 Hp (22.1 kW) at 5850 rpm |
| Fuel System: Two stroke low pressure direct injection (TLDI) |
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The Tohatsu MD30B2 is a two-stroke,
three-cylinder outboard engine featuring TLDI fuel injection. The engine
displacement measures 42.5 cubic inches or 697 cc, achieved through a
cylinder bore of 2.68 inches (68.0 mm) and a piston stroke of 2.52
inches (64.0 mm). The powerhead produces a maximum output of 30.0 Hp,
equivalent to 22.1 kW. The engine is designed to operate within a
wide-open throttle range of 5150 to 5850 rpm.
The idle speed is adjustable among three settings, commonly 700, 800, or
900 rpm, with a specific trolling speed of 800 rpm. The compression
ratio is specified at 7.2:1. The firing order is 1-2-3. Lubrication is
provided by an oil injection system, which automatically meters oil from
a separate tank directly into the fuel mixture. The engine utilizes a
water cooling system with a thermostat and expels exhaust through the
propeller hub. Ignition is handled by an inductive system. Starting is
facilitated by an electric starter.
The foundation of the MD30B2 engine is its cylinder block, machined to
precise tolerances. The cylinder bore inside diameter is specified at
2.677 to 2.679 inches, or 68.00 to 68.05 mm. Pistons are manufactured
with a skirt diameter of 2.674 to 2.675 inches (67.92 to 67.96 mm) ,
establishing a piston-to-cylinder clearance of 0.0031 to 0.0047 inch
(0.08 to 0.12 mm).
The piston pin bore inside diameter measures 0.6693 to 0.6695 inch
(17.001 to 17.007 mm) , resulting in a piston-to-piston pin clearance of
0.0002 to 0.0005 inch (0.005 to 0.013 mm). The piston ring set includes
a top and second ring, both with an end gap of 0.015 to 0.021 inch (0.38
to 0.53 mm) and a side clearance of 0.0016 to 0.0032 inch (0.04 to 0.08
mm).
As a two-stroke engine utilizing TLDI technology, the Tohatsu MD30B2
does not employ a traditional poppet valvetrain. Intake and exhaust
functions are managed by ports in the cylinder wall, timed by the
movement of the piston. The TLDI system replaces a carburetor, using
precisely controlled air and fuel injection for improved combustion
efficiency.
The MD30B2 features a Two-stroke Low pressure Direct Injection (TLDI)
fuel system. This system injects fuel directly into the combustion
chamber, resulting in more complete combustion, greater fuel efficiency,
and reduced exhaust emissions compared to conventional two-stroke
outboards.
The engine operates on unleaded gasoline with a minimum octane rating of
87 (Research Octane Number of 91). Fuel consumption is rated at 12.0
liters per hour at wide-open throttle. The engine is typically supplied
with a 6.6-gallon or 25-liter external remote fuel tank.
Lubrication for the MD30B2 is managed by an automatic oil injection
system. Engine oil meeting Tohatsu's genuine specifications or a
recommended equivalent is drawn from a separate oil tank and injected
into the fuel stream by a precision pump.
The engine oil capacity for the separate tank is 2.1 US quarts or 2.0
liters. This system ensures a consistent and correct oil-to-fuel ratio
across all operating conditions, eliminating the need for pre-mixing
fuel.
Cooling is accomplished through a forced water system, drawing water
from the body of water in which the engine is operating. A water pump,
driven by the driveshaft, circulates cooling water through passages in
the engine block and cylinder head. A thermostat regulates the flow to
maintain optimal operating temperatures.
A cooling water check port on the engine allows the operator to visually
confirm that the water pump is functioning correctly. A freshwater
flushing attachment is available for rinsing the cooling passages after
operation in salt or brackish water.
| Mid Section and Lower Unit |
The mid section connects the powerhead to the lower unit and houses the
driveshaft. The exhaust system is designed to route gases through the
propeller hub for quieter operation. The lower unit contains a spiral
bevel gear reduction system with a ratio of 1.85:1.
The gear shift mechanism is a dog clutch type, providing forward,
neutral, and reverse functions. The gearcase holds 0.53 US quart or 0.50
liter of gear lubricant, which must meet API GL5 specifications with a
viscosity of SAE 80 or SAE 90.
The MD30B2 is equipped with a hydraulic power trim and tilt system,
operated by a switch on the remote control or tiller handle. This system
allows for effortless adjustment of the engine's angle for optimal
performance and shallow water operation.
The maximum tilt angle is 74 degrees, and the steering angle is 70
degrees. A manual release valve is provided to allow manual tilting of
the engine in the event of a battery failure or electrical issue. A tilt
stopper mechanism locks the engine in the fully raised position for
trailering or mooring.
The MD30B2 is fitted with a three-bladed aluminum propeller. A range of
propeller diameters and pitches are available to match the engine to
specific boat and load conditions. Available diameters include 10.9
inches (278 mm), 11 inches (279 mm), 11.4 inches (290 mm), and 12.2
inches (311 mm).
Available pitch options range from 9 to 15 inches, including 9 (229 mm),
11 (279 mm), 12 (305 mm), 13 (330 mm), 14 (356 mm), and 15 (381 mm). The
correct propeller must be selected to allow the engine to operate within
its recommended full-throttle range of 5150 to 5850 rpm. The propeller
nut is to be torqued to 35 Nm (25 lb-ft) and secured with a new split
pin.
The Tohatsu MD30B2 is offered in both EPTO (Electric Power Tilt &
Remote) and EFTO (Electric & Tiller) configurations, both with a long
shaft. The EPTO model has an overall length of 24.8 inches (630 mm) and
an overall width of 13.6 inches (345 mm).
The EFTO model, with its tiller handle, has an overall length of 44.1
inches (1120 mm) and an overall width of 15.1 inches (385 mm). Both
models share the same overall height of 53.3 inches (1355 mm) and a
transom height of 20.9 inches (530 mm). Weight varies by configuration.
The EPTO model weighs 208 lbs (94.5 kg), while the EFTO model weighs 215
lbs (97.5 kg).
Routine maintenance is essential for reliable operation. The engine
operates on unleaded gasoline with a minimum octane rating of 87. The
separate oil injection tank holds 2.1 US quarts (2.0 liters) of genuine
Tohatsu two-stroke outboard oil or a recommended equivalent. The
gearcase capacity is 0.53 US quart (0.50 liter) of hypoid gear oil
meeting API GL5, SAE 80 or 90 specifications. The specified spark plug
is NGK IZFR6J or IZFR6Q, with a gap setting of 0.031 to 0.035 inch, or
0.8 to 0.9 mm.
A maintenance schedule guides service intervals. Every 50 hours of
operation, gear oil level and propeller condition should be checked.
Every 100 hours, inspections should include the battery, fuel filter,
spark plugs, fuel line, anodes, drive belt, air filter, fuel tank,
cooling system, and water pump, along with a gear oil change. The
high-pressure fuel filter and spark plugs should be replaced every 200
hours.
Precise fastener torque is critical for proper engine assembly and safe
operation. Critical torque specifications include the cylinder head bolt
at 32 Nm or 23.0 lb-ft. Crankcase bolts require 25 Nm (18.0 lb-ft). The
flywheel nut demands 150 Nm (108.0 lb-ft). The propeller nut is torqued
to 35 Nm (25.0 lb-ft). Gear case bolts are set at 20 Nm (14.0 lb-ft).
When mounting the outboard motor to the boat transom, the mounting bolts
must be tightened to 30 Nm (13 lb-ft) to ensure the motor is securely
fastened. Other specifications include the exhaust cover bolt at 12 Nm
(9.0 lb-ft), compressor head bolt and air box bolt at 9 Nm (7.0 lb-ft),
drive pulley nut at 100 Nm (74.0 lb-ft), and spark plugs at 25 Nm (18.0
lb-ft).
The versatility of the Tohatsu MD30B2 makes it suitable for a wide range
of watercraft. Its power output and torque characteristics are
well-suited for larger aluminum fishing boats, rigid inflatable boats,
skiffs, and smaller center console boats up to approximately six meters
in length. The EFTO tiller handle model is popular for boats where the
operator prefers to sit aft for precise maneuvering, such as in bass
boats or jon boats used in confined waters.
The EPTO remote steering model integrates cleanly with center console or
dual console layouts, allowing for a more forward helm position. The
engine's advanced TLDI technology appeals to operators seeking the
power-to-weight advantages of a two-stroke combined with the fuel
economy and low emissions profile of a four-stroke, making it suitable
for both recreational and light commercial use. Its robust construction
and oil injection system also make it a reliable choice for demanding
applications.
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