Tohatsu MFS6CD Specifications
| Engine Model: Tohatsu MFS6CD |
| Engine Type: 4-stroke 1-cylinder OHV gasoline outboard engine |
| Total Displacement: 7.5 cu.in (123 cc) |
| Rated Engine Power: 6 Hp (4.4 kW) at 6000 rpm |
| Fuel System: Carburetor |
____________________________________________________________________________________
The Tohatsu MFS6CD is a four-stroke,
single-cylinder outboard engine featuring an OverHead Valve (OHV)
design. The engine displacement measures 7.5 cubic inches or 123 cc,
achieved through a cylinder bore of 2.32 inches (59.0 mm) and a piston
stroke of 1.77 inches (45.0 mm). The powerhead produces a maximum output
of 6.0 Hp, equivalent to 4.4 kW. The engine is designed to operate
within a wide-open throttle range of 5000 to 6000 rpm, with a trolling
speed of 1100 rpm and an idle speed of 1300 rpm.
The compression ratio is specified at 9.6:1. Lubrication is provided by
a wet sump system. The engine utilizes a water-cooled cooling system and
expels exhaust through the propeller hub. Ignition is handled by a
flywheel magneto Capacitor Discharge Ignition (CDI) system. Starting is
accomplished through a manual recoil starter. The electrical system
operates on a 12-volt basis, with an alternator rated at 60 W and 5 A
available for battery charging.
The foundation of the MFS6CD engine is its cylinder block, machined to
precise tolerances. The cylinder bore inside diameter is specified at
2.322 to 2.324 inches, or 59.00 to 59.03 mm, with a maximum allowable
out-of-round measurement of 0.002 inch (0.050 mm). Crankshaft runout
must not exceed 0.002 inch (0.050 mm). Crank pin outside diameter
measures 1.1791 to 1.1793 inches (29.95 to 29.98 mm).
Connecting rods feature a big end oil clearance of 0.0016 to 0.0026 inch
(0.040 to 0.066 mm) and a big end side clearance of 0.008 to 0.016 inch
(0.20 to 0.40 mm). The small end inside diameter measures 0.6301 to
0.6303 inch (16.006 to 16.014 mm). Pistons are manufactured with a skirt
diameter of 2.321 to 2.322 inches (58.95 to 58.97 mm), establishing a
piston-to-cylinder clearance of 0.0008 to 0.0032 inch (0.020 to 0.055
mm). The piston pin outside diameter is 0.6301 to 0.6303 inch (15.995 to
16.000 mm), fitting into the piston with a clearance of 0.0001 to 0.0005
inch (0.003 to 0.012 mm).
The piston ring set includes a top ring with an end gap of 0.006 to
0.014 inch (0.15 to 0.35 mm) and a side clearance of 0.0016 to 0.0032
inch (0.04 to 0.08 mm). The second ring end gap measures 0.012 to 0.020
inch (0.30 to 0.50 mm) with a side clearance of 0.0012 to 0.0028 inch
(0.03 to 0.07 mm). The oil ring end gap is 0.008 to 0.016 inch (0.20 to
0.40 mm) with a side clearance of 0.0004 to 0.0071 inch (0.01 to 0.18
mm).
The cylinder head assembly incorporates the OHV valvetrain and must
remain within a warp limit of 0.002 inch (0.050 mm). Valve clearances
require adjustment, with intake valves set to 0.002 to 0.006 inch (0.06
to 0.14 mm) and exhaust valves set to 0.004 to 0.008 inch (0.11 to 0.19
mm).
Intake valve stem outside diameter measures 0.2154 inch (5.47 mm), while
exhaust valve stems are slightly smaller at 0.2142 inch (5.44 mm). Both
intake and exhaust valve guides share an inside diameter of 0.2165 inch
(5.50 mm). This results in a stem-to-guide clearance of 0.0008 to 0.0017
inch (0.020 to 0.044 mm) for intake valves and 0.0018 to 0.0028 inch
(0.045 to 0.072 mm) for exhaust valves.
Valve seat width is 0.0315 inch (0.8 mm) for both intake and exhaust.
The valve springs have a free length of 1.38 inches (35.0 mm). Camshaft
profiles for both intake and exhaust lobes measure 1.115 inches (28.33
mm). The camshaft journal outside diameter is 0.5504 inch (13.98 mm).
The MFS6CD employs a vertical butterfly-type carburetor for fuel
delivery. The fuel pump is mechanically operated. The defining feature
of the CD model is its integral fuel tank, which has a capacity of 1.20
US quarts or 1.15 liters.
This built-in tank eliminates the need for an external fuel tank and
separate fuel line, simplifying transport and setup. The engine operates
on unleaded gasoline with a minimum octane rating of 90 (Research Octane
Number). Fuel consumption is rated at 1.7 liters per hour at wide-open
throttle.
Engine lubrication is maintained through a wet sump system. The system
requires 0.47 US quart or 0.45 liter of engine oil meeting API service
classifications SE, SF, SG, SH, SJ, SL, or SM. Recommended viscosity
grades include SAE 10W-30 and 10W-40 for normal operating conditions. A
low oil pressure warning indicator alerts the operator to unsafe
operating conditions.
Cooling is accomplished through a forced water system, drawing water
from the body of water in which the engine is operating. A water pump
with a stainless steel housing , 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
between 115 and 125 F.
| 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 2.15:1.
The gear shift mechanism is a dog clutch type, providing forward,
neutral, and reverse functions through a side-mounted shift lever. The
gearcase holds 0.21 US quart or 0.20 liter of gear lubricant, which must
meet API GL5 specifications with a viscosity of SAE 80 or SAE 90.
The MFS6CD features a manual trim and tilt system. Trim angle adjustment
is achieved by repositioning a thrust rod in one of six available
positions on the stern bracket, which also provides a shallow water
drive setting. The maximum tilt angle is 75 degrees.
The steering angle is 150 degrees, and an adjustable steering friction
setting allows the operator to customize steering resistance. A tilt
stopper mechanism locks the engine in the fully raised position for
trailering or mooring.
The MFS6CD is fitted with a three-bladed aluminum propeller as standard
equipment. Propeller diameters range from 7.8 to 7.9 inches (188 to 200
mm) depending on pitch selection. A range of pitch options from 6 to 9
inches (152 to 229 mm) allows adaptation to different boat loads and
applications.
Standard pitch offerings include 6, 7, 8, and 9 inches (152, 178, 203,
and 229 mm). The propeller nut must be torqued to the correct
specification and secured with a new split pin. Propeller selection must
allow the engine to operate within its recommended full-throttle range
of 5000 to 6000 rpm.
The Tohatsu MFS6CD is offered in short, long, and extra-long shaft
configurations. Overall length measures 30.8 inches or 785 mm, slightly
longer than the remote tank version due to the integral fuel tank
design. Overall width is 13.5 inches (345 mm). The short shaft version
has an overall height of 42 inches (1068 mm) with a transom height of 17
inches (435 mm). The long shaft version stands 47 inches (1195 mm) tall
with a 22-inch (560-mm) transom height.
The extra-long shaft version has an overall height of 52 inches (1320
mm) and a transom height of 27 inches (685 mm). Weight varies by shaft
length. The short shaft model weighs 57.3 lbs (26.0 kg), the long shaft
model weighs 59.5 lbs (27.0 kg), and the extra-long shaft model weighs
61.7 lbs (28.0 kg).
Routine maintenance is essential for reliable operation. The engine
operates on unleaded gasoline with a minimum octane rating of 90. The
engine oil capacity is 0.47 US quart (0.45 liter) of SAE 10W-30 or
10W-40 oil meeting API service classifications SE through SM. The
gearcase capacity is 0.21 US quart (0.20 liter) of hypoid gear oil
meeting API GL5, SAE 80 or 90 specifications.
Ignition timing is set at 25 degrees Before Top Dead Center. The
specified spark plug is NGK DCPR6E, 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, propeller condition, and
starter rope function should be checked.
Every 100 hours, inspections should include spark plugs, fuel line, fuel
tank cleaning, fuel filter, anodes, engine oil change, cooling system,
water pump, valve clearance, carburetor, and ignition timing, along with
a gear oil change. Spark plug replacement is recommended every 200
hours.
Precise fastener torque is critical for proper engine assembly and safe
operation. Critical torque specifications include the cylinder head bolt
at 25 Nm or 18.0 lb-ft. Connecting rod bolts require 12 Nm (9.0 lb-ft).
The flywheel nut demands 50 Nm (37.0 lb-ft).
The oil drain bolt is torqued to 18 Nm (13.0 lb-ft). Oil pan bolts and
pivot bolts are both set at 25 Nm (18.0 lb-ft). The pivot adjust nut
requires 10 Nm (7.5 lb-ft). The oil pressure switch is torqued to 9 Nm
(7.0 lb-ft).
Recoil starter bolts are tightened to 4 Nm (3.0 lb-ft). Stern bracket
nuts require 13 Nm (9.0 lb-ft). Power unit mounting bolts are set at 7
Nm (5.5 lb-ft). When mounting the outboard to the boat transom, the
clamp screws or mounting bolts must be tightened to secure the motor
firmly. Spark plugs are installed at 18 Nm or 13.0 lb-ft.
The Tohatsu MFS6CD, with its integral fuel tank, is ideally suited for a
range of small, lightweight watercraft where simplicity and portability
are paramount. Its compact dimensions and low weight make it a perfect
choice for dinghies and tenders used as auxiliary boats for larger
vessels, eliminating the need to carry a separate fuel tank and hose. It
is also widely used on small inflatable boats, where its self-contained
design reduces setup time and clutter.
For recreational anglers operating small jon boats or lightweight
fishing skiffs, the MFS6CD provides ample power for maneuvering in
protected waters without the complexity of an external tank. The engine
is also available in a version compatible with remote controls, allowing
for flexible helm installation on small center console boats. The
four-stroke engine's quiet operation and low emissions make it suitable
for use in environmentally sensitive areas, and the available alternator
provides the capability to charge a small battery for running lights or
other 12-volt accessories.
____________________________________________________________________________________
| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
