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Tohatsu M25H Specifications
| Engine Model: Tohatsu M25H |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 26.1 cu.in (429 cc) |
| Rated Engine Power: 25 Hp (18.4 kW) at 5500 rpm |
| Fuel System: Carburetor |
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| General Technical Data |
The Tohatsu M25H is a two-cylinder,
loop-charged two-stroke outboard delivering 25 horsepower. Offered in
two primary configurations - manual start with tiller (MF) and electric
start with remote control (EP) - this engine is engineered for
reliability and ease of operation. It shares its powerhead and many
components with the larger M30H model and has earned a reputation among
commercial fishermen and recreational boaters worldwide for its
incredible power relative to its manageable weight and its unprecedented
reliability. The design focuses on simplicity and proven two-stroke
technology, making it a robust and trusted choice for a variety of
on-water activities.
The Tohatsu M25H represents a well-engineered and dependable outboard
option. Its two-cylinder design provides smooth operation with good fuel
economy, a direct benefit of its loop-charged induction system. The CD
ignition system ensures quick and reliable starts in various conditions.
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.
A standard 12V, 80W alternator on electric start models provides power
for essential electronics. Essential safety features like a safety
lanyard and start-in-gear protection are standard across all models.
Engine Model: Tohatsu M25H MF, M25H EP
Engine Type: 2-Stroke.
Number of Cylinders: 2.
Bore x Stroke: 68 mm x 59 mm (2.68 in x 2.32 in).
Piston Displacement: 429 cc (26.16 cu in).
Power Output: 18.4 kW (25 HP).
Full Throttle Operating Range: 5000-6000 r/min.
Idle Speed in Neutral Gear: 950 r/min.
Minimum Trolling Speed in Forward Gear: 800 r/min.
Exhaust System: Through-hub exhaust.
Cooling System: Water cooling with thermostat control.
Lubrication System: Gasoline oil mixed type (Pre-mixed fuel).
Starting System: Manual (MF model) / Electric starter motor (EP model).
Ignition System: Flywheel Magneto CDI (Capacitor Discharge Ignition).
Spark Plugs: NGK B7HS-10 or BR7HS-10.
Spark Plug Gap: 0.9-1.0 mm (0.035-0.039 in).
Alternator: 12V, 80W, 6.7A (Standard on Electric Start Models).
Steering (MF): Tiller Handle.
Steering (EP): Remote Control.
Steering Angle: 80 degrees.
Trim System: Manual trim and tilt.
Trim Angle: -9.5 to 15.5 degrees.
Trim Position: 6.
Tilt Up Angle: 58 degrees.
Gear Shift: Dog clutch (F-N-R).
Gear Reduction Ratio: 1.92 (12:23).
Fuel: Unleaded Regular Gasoline with an anti-knock index (R+M/2) of 87
or higher, or a Research Octane Number (RON) of 91 or higher.
Fuel Tank Capacity: 25 L (6.6 US gal) Separate fuel tank.
Engine Oil: Genuine motor oil or recommended one (TCW-III).
Fuel-to-Engine Oil Mixing Ratio: 50:1.
Gear Oil: API GL-5, SAE 80-90.
Gear Oil Capacity: 0.36 L (0.38 qt).
| Powerhead |
The M25H features a loop-charged, two-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 CD 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.
| Fuel System |
The fuel system is carbureted and designed to run on standard 87-octane unleaded gasoline. A separate 25-liter fuel tank is provided with the outboard. A fuel filter is located within the engine and inside the fuel tank, requiring periodic inspection and cleaning.
| Lubrication System |
The lubrication system requires fuel pre-mixed at a 50:1 ratio with TCW-III certified two-stroke outboard oil. The engine does not feature an automixing oil injection system.
| Cooling System |
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. A cooling water check port on the front of the drive shaft housing allows the operator to verify proper water flow.
| Mid Section and Lower Unit |
The M25H is fitted with a durable mid section and lower unit housing a forward-neutral-reverse dog clutch. The gear reduction ratio is 1.92:1 (12:23). The recommended gear oil is an API GL-5, SAE 80-90 grade, with a total capacity of 0.36 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.
| Trim and Tilt System |
The M25H features a manual trim and tilt system. This system allows the operator to adjust the motor's angle through six trim positions, ranging from -9.5 to 15.5 degrees, for optimal boat performance.
The motor can be tilted up to 58 degrees for beaching, launching, or trailering. A shallow water drive feature (thrust rod) is also standard, allowing the engine to be operated at a shallower angle for navigating in shallow water.
| Propeller Information |
The recommended propeller selection range for the M25H is from 8 to 14 inches of pitch. The correct propeller must be selected so that the engine operates within its wide-open throttle (WOT) range of 5000-6000 r/min under a normal load for optimal performance and engine longevity.
The standard propeller is made of aluminum. When installing or removing the propeller, a block of wood should be placed between the propeller blade and the anti-ventilation plate to hold it, and a new split pin must always be used.
| Dimensions and Weight |
Overall Length (MF): 884 mm (34.8 in)
Overall Length (EP): 600 mm (23.6 in)
Overall Width (MF): 430 mm (16.9 in)
Overall Width (EP): 373 mm (14.7 in)
Overall Height (Short Shaft): 1124 mm (44.3 in)
Overall Height (Long Shaft): 1251 mm (49.3 in)
Overall Height (Ultra Long Shaft): 1378 mm (54.3 in)
Transom Height (Short Shaft): 435 mm (17.1 in)
Transom Height (Long Shaft): 562 mm (22.1 in)
Transom Height (Ultra Long Shaft): 689 mm (27.1 in)
Weight (MF Short Shaft): 51 kg (112 lb)
Weight (EP Short Shaft): 54 kg (119 lb)
Weight (MF Long Shaft): 51.5 kg (116 lb)
Weight (EP Long Shaft): 55.5 kg (122 lb)
Weight (MF Ultra Long Shaft): 54 kg (119 lb)
| Maintenance Data |
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 0.9-1.0 mm (0.035-0.039 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 12
Months: 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. Off-season storage and
pre-season checks should be performed as outlined in the owner's manual.
| Tightening Torques |
Gear Oil Plug: 4 Nm (3 lb-ft)
Propeller Nut: 25 Nm (18 lb-ft)
Spark Plug: 27 Nm (20 lb-ft)
| Boat Applications |
Fishing Boats: A top choice for small aluminum tiller-steered boats, jon boats, and lightweight center consoles, favored by commercial fishermen worldwide. 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. A specialized jet drive version (M25H JET) is also available for operation in extremely shallow water and weed-choked areas.
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