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Tohatsu M9.8B 2-Stroke Specifications
The Tohatsu M9.8B is a 2-stroke 2-cylinder forced water-cooled shallow-water drive gasoline outboard engine with a rated power of 9.8 hp (7.2 kW) at 5000-6000 rpm. The engine cylinder bore is 1.97" (50 mm) and piston stroke is 1.69" (43 mm). A 10.3 cubic inches (169 cc) outboard motor has a carburetor fuel system, starting system with manual starter, flywheel magneto capacitor discharge ignition system, dog clutch shift system, manual tilt, and handle tiller or remote control steering. The fuel tank capacity is 3.2 gal (12 liters). The propeller is made of aluminum and it has three blades.
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| General Technical Data |
Engine Model ................ Tohatsu M9.8B MF, M9.8B EF
Engine Type ................ 2-stroke two-cylinder gasoline outboard engine
Number of Cylinders ................ 2
Displacement, cu.in (cc) ................ 10.3 (169)
Cylinder Bore, in (mm) ................ 1.97 (50.0)
Piston Stroke, in (mm) ................ 1.69 (43.0)
Maximum Engine Power, hp (kW) ................ 9.8 (7.2)
Maximum Engine Speed, rpm ................ 5000-6000
Idle Speed, rpm ................ 950
Trolling Speed, rpm ................ 750
Lubrication System ................ Engine oil mixed gasoline
Exhaust System ................ Through hub exhaust
Cooling System ................ Forced water cooling
Ignition System ................ Flywheel magneto CDI
Starting System ................ Manual or electric
| Dimensions and Weight |
Overall Length, in (mm) ................ 31.2 (790)
Overall Width, in (mm) ................ 12.6 (320)
Overall Height (Short Shaft), in (mm) ................ 39.2 (995)
Overall Height (Long Shaft), in (mm) ................ 44.2 (1120)
Overall Height (Extra Long Shaft), in (mm) ................ 49.2 (1250)
Transom Height (Short Shaft), in (mm) ................ 17 (435)
Transom Height (Long Shaft), in (mm) ................ 22 (560)
Transom Height (Extra Long Shaft), in (mm) ................ 27 (690)
Outboard Weight (M9.8B MF, Short Shaft), lbs (kg) ................ 57.0 (26.0)
Outboard Weight (M9.8B EF, Short Shaft), lbs (kg) ................ 64.0 (29.0)
Outboard Weight (M9.8B MF, Long Shaft), lbs (kg) ................ 60.0 (27.0)
Outboard Weight (M9.8B EF, Long Shaft), lbs (kg) ................ 66.0 (30.0)
Outboard Weight (M9.8B MF, Extra Long Shaft), lbs (kg) ................ 62.0 (28.0)
| Fuel System |
Fuel System Type ................ Carburetor
Carburetor Model ................ Keihin Kikaki
Fuel Type ................ Unleaded gasoline (87 or 91 octane minimum)
Fuel Consumption, L/hr ................ 4.3
Fuel Tank Capacity, gal (L) ................ 3.2 (12.0)
| Gear Housing |
Shift System ................ Dog clutch
Gear Shift ................ F-N-R
Gear Ratio ................ 2.08:1
Gear Oil Capacity, qts (L) ................ 0.34 (0.32)
| Mid Section |
Trim System ................ Manual Trim and Tilt
Trim Position ................ 6
Transom Height (Short Shaft), in (mm) ................ 17 (435)
Transom Height (Long Shaft), in (mm) ................ 22 (560)
Transom Height (Extra Long Shaft), in (mm) ................ 27 (690)
Steering System (Std) ................ Tiller handle
Steering System (Opt) ................ Remote control
Tilt Angle (Max), deg ................ 75
| Propeller Information |
Diameter, in (mm) ................ 8.5 (216), 8.9 (226)
Pitch, in (mm) ................ 6.5 (165), 7 (178), 7.5 (190), 8.3 (211), 10 (254)
Number Of Blade ................ 3
Material ................ Aluminum
| Maintenance Data |
Engine Fuel Type ................ Unleaded 87 or 91 octane minimum
Engine Oil Type ................ Genuine motor oil or recommended one (TCW-III)
Engine Oil and Fuel Ratio ................ Unleaded Gasoline 50. Genuine 2-stroke Engine Oil 1
Gear Lubricant Type ................ Genuine Gear Oil or API GL5, SAE 80, SAE 90
Gearcase Capacity, qts (L) ................ 0.34 (0.32)
Ignition Timing, degrees ................ 24 BTDC
Spark Plug Type ................ NGK BPR7HS-10
Spark Plug Gap, in (mm) ................ 0.035-0.039 (0.9-1.0)
| Service Data |
Cylinder Bore Inside Diameter, in (mm) ................ 1.968-1.969 (50.00-50.01)
Piston to Cylinder Clearance, in (mm) ................ 0.0008-0.0020 (0.02-0.05)
Top Ring End Gap, in (mm) ................ 0.007-0.013 (0.18-0.33)
Second Ring End Gap, in (mm) ................ 0.007-0.013 (0.18-0.33)
Top Ring Side Clearance, in (mm) ................ 0.0004-0.0020 (0.01-0.05)
Second Ring Side Clearance, in (mm) ................ 0.0004-0.0020 (0.01-0.05)
Piston to Piston Pin Clearance, in (mm) ................ 0.0002-0.0031 (0.01-0.08)
Connecting Rod Big End Side Clearance, in (mm) ................ 0.008-0.016 (0.20-0.40)
| Service Intervals |
Check Spark Plug ................ Every 50 hours
Check Fuel Line ................ Every 50 hours
Clean Fuel Tank ................ Every 50 hours
Check Anodes ................ Every 50 hours
Check Gear Oil ................ Every 50 hours
Check Propeller ................ Every 50 hours
Check Starter Rope ................ Every 50 hours
Check Cooling System ................ Every 100 hours
Check Water Pump ................ Every 100 hours
Check Carburetor ................ Every 100 hours
Ajust Ignition Timing ................ Every 100 hours
Change Gear Oil ................ Every 200 hours
Replace Spark Plug ................ Every 200 hours
Replace Water Pump Impeller ................ Every 200 hours
| Tightening Torques |
Cylinder head bolt, Nm (lb-ft) ................ 10 (7.2)
Magneto nut, Nm (lb-ft) ................ 60 (43.3)
Crankcase bolt, Nm (lb-ft) ................ 13.5 (10.1)
Intake manifold bolt, Nm (lb-ft) ................ 13.5 (10.1)
Exhaust cover bolt, Nm (lb-ft) ................ 10 (7.2)
Bracket nut, Nm (lb-ft) ................ 15 (11.0)
Gearcase bolt, Nm (lb-ft) ................ 10 (7.2)
Propeller shaft housing, Nm (lb-ft) ................ 10 (7.2)
Drive shaft housing bolt, Nm (lb-ft) ................ 10 (7.2)
Spark plug, Nm (lb-ft) ................ 27 (20.0)
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| Engines Technical Specifications |