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Evinrude 9.9 Hp 4 stroke Specs
| Engine Model: Evinrude 9.9 Hp |
| Engine Type: 4-stroke in-line 2-cylinder OHC gasoline outboard engine |
| Total Displacement: 12.8 cu.in (211 cc) |
| Rated Engine Power: 9.9 Hp (7.4 kW) at 6000 rpm |
| Fuel System: Carburetor or Electronic fuel injection (EFI) |
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| General Technical Data |
The Evinrude 9.9 HP four-stroke outboard is a
reliable and smooth-running engine, highly regarded for propelling small
fishing boats, dinghies, and sailboats. Its OHC design contributes to
efficient operation and reduced noise levels compared to older
two-stroke models. While later models may feature Electronic Fuel
Injection (EFI) for improved starting and fuel economy, many versions
utilize a simple and serviceable carbureted fuel system.
The engine is offered with both manual and electric start options and is
available in different shaft lengths to accommodate various transom
heights. Its lightweight design, with a weight range of approximately 87
to 93 lbs, ensures portability and ease of use for boaters who
frequently trailer or launch their vessels.
The Evinrude 9.9 HP four-stroke is a four-stroke, in-line 2-cylinder
powerhead with a single overhead camshaft (OHC). It delivers 9.9 Hp at
7.4 kW. The engine displacement is 12.87 cubic inches (211 cc). The
cylinder bore measures 2.22 inches (56.6 mm) and the piston stroke is
1.65 inches (42.0 mm). The engine is designed to operate within a full
throttle RPM range of 5000 to 6000 RPM. The gear ratio for this model is
2.08:1. It is available with a standard 15-inch shaft or a long 20-inch
shaft to match the transom height of the boat.
| Cylinder Block |
The cylinder block houses the two cylinders in an in-line configuration. The crankshaft rotates on precision journals, with the top journal diameter specified between 1.2200 and 1.2204 inches (30.99 to 31.00 mm) and the bottom journal diameter within the same range.
The rod crankpin has a diameter between 1.1398 and 1.1401 inches (28.95 to 28.96 mm). Piston ring end gap for the top two rings should measure between 0.006 and 0.014 inches (0.15 to 0.36 mm), and the maximum side clearance for the piston ring groove is 0.004 inches (0.10 mm).
| Cylinder Head |
The cylinder head is a separate component that contains the valves and combustion chambers, sealed to the block with a precision-machined gasket surface. The valvetrain is controlled by an overhead camshaft. Proper valve clearance is critical for engine performance and longevity.
The intake valve clearance is set at 0.003 inches (0.08 mm), while the exhaust valve clearance is set at 0.005 inches (0.12 mm). Camshaft lobe dimensions are precisely controlled, with the intake lobe at 0.954 ± 0.002 inches (24.222 ± 0.05 mm) and the exhaust lobe at 0.955 ± 0.002 inches (24.262 ± 0.05 mm).
| Fuel System |
The fuel system on these four-stroke models is either a carbureted design or, on later iterations, an Electronic Fuel Injection (EFI) system. The carbureted system mixes air and fuel in a precise ratio before it enters the combustion chamber. It includes a fuel pump, fuel filter, and carburetor with idle mixture and speed adjustment screws. The idle RPM, when in gear, is set at 900 ± 50 RPM.
The EFI system, where equipped, uses an electronic control unit to manage fuel delivery via injectors, optimizing fuel atomization for improved combustion efficiency, easier starting, and reduced emissions. The fuel pump diaphragm and check valves are critical components that require inspection and eventual replacement as part of routine maintenance.
| Lubrication System |
As a four-stroke engine, the Evinrude 9.9 HP features a dedicated sump for engine oil, which is circulated by a pump to lubricate the crankshaft, camshaft, valve train, and cylinder walls. This system ensures that clean oil is constantly supplied to critical moving parts.
The total oil capacity is 27 fluid ounces (800 milliliters). The recommended oil is Evinrude/Johnson 5W40 Ultra 4-Stroke oil, specifically formulated for the demands of outboard engines. The oil filter should be replaced at each oil change to maintain optimal filtration and engine protection.
| Cooling System |
The engine employs a water-cooling system, common to all outboard motors, to maintain optimal operating temperatures. A rubber-impeller water pump, located in the lower unit, draws water from the body of water in which the boat is operating. This water is then circulated through water passages within the cylinder block and head to absorb excess heat before being exhausted, often with the exhaust gasses.
A tell-tale stream of water from the back of the engine confirms that the water pump is functioning and the cooling system is operational. The water pump impeller requires replacement approximately every two years regardless of usage, as the rubber components become brittle over time.
| Mid Section and Lower Unit |
The midsection, also known as the driveshaft housing, connects the powerhead to the lower unit and houses the exhaust passage and the vertical driveshaft. The lower unit, or gearcase, contains the forward, neutral, and reverse gears, as well as the water pump assembly. The gearcase is filled with a high-viscosity lubricant to protect the gears and bearings.
The gear ratio for this model is 2.08:1, which provides a good balance of thrust and propeller speed. An anode, often integrated into the trim tab, is located on the lower unit to protect metal components from galvanic corrosion in saltwater environments. The shift rod on four-stroke models extends up to the carburetor area and must be disconnected near the shift lever before lower unit removal can be completed.
| Trim and Tilt System |
The Evinrude 9.9 HP outboard is equipped with a manual tilt system. This allows the operator to tilt the engine out of the water when not in use, for mooring in shallow water, or for trailering. The system uses a manual release lever and tilt pin to secure the engine at the desired angle. Some models may offer an optional power trim and tilt for on-the-fly adjustment of the engine angle to optimize boat performance and draft, though this is less common on smaller Hp engines.
| Propeller Information |
Propeller selection is crucial for achieving optimal engine performance. The Evinrude 9.9 HP outboard uses propellers with a 13-spline count to match the gearcase. Common propeller sizes for this engine include diameters and pitches such as 9.25 inches in diameter with an 8, 9, 10, or 11-inch pitch, often in a 3-blade aluminum configuration.
The correct propeller allows the engine to operate within its recommended full-throttle RPM range of 5000 to 6000 RPM. A lower pitch propeller provides more thrust for heavier loads or planing, while a higher pitch is suited for lighter loads and higher top speeds. Right-hand rotation is standard for these applications.
| Dimensions and Weight |
The Evinrude 9.9 HP four-stroke outboard is designed to be compact and lightweight for its power class. The physical dimensions vary slightly depending on the shaft length and starter type. The overall weight of the engine is approximately 39 kg (87 lbs) for manual start models and up to 42 kg (93 lbs) for models equipped with electric start. This relatively low weight enhances portability, making it a practical choice for small boat owners.
| Maintenance Data |
Regular maintenance is essential for the longevity and reliable operation of the Evinrude 9.9 HP outboard. Key maintenance tasks include changing the engine oil and filter at specified intervals, replacing the gearcase lubricant, and inspecting the water pump impeller for wear or damage. The fuel system, including the fuel filter and fuel lines, should be inspected periodically, especially if the engine is not used regularly.
Spark plugs should be checked, cleaned, and gapped according to specifications. Lubricating all moving parts on the tiller handle, steering pivot, and transom mounting brackets is also recommended to prevent corrosion and ensure smooth operation. Valve adjustment should be performed as part of routine tune-up procedures.
| Tightening Torques |
Cylinder head bolts are secured to a specification of 216 to 240 lb-in.
This moderate torque value ensures the cylinder head gasket is
compressed evenly to create a positive seal against combustion pressures
and coolant passages while preventing damage to the aluminum threads or
distortion of the cylinder head itself.
Connecting rod screws, which secure the rod caps to the crankshaft,
require a torque of 48 to 60 lb-in. This critical fastener must be
tightened precisely to maintain the bearing clearance and withstand the
high dynamic loads of the reciprocating assembly without stretching or
failing.
The fasteners securing the crankcase to the cylinder block have two
distinct torque specifications. The first range is 145 to 170 lb-in for
the main crankcase bolts. A second set of fasteners, likely smaller or
with a different function, is tightened to a lower range of 60 to 96
lb-in. These values ensure the crankcase halves are sealed properly and
the crankshaft main bearings are held securely in their bores.
Spark plugs are torqued to 13 lb-ft. This specification is sufficient to
crush the gasket and provide a good seal against combustion gases while
ensuring efficient heat transfer from the plug to the cylinder head.
Over-tightening can damage the threads in the aluminum head, while
under-tightening can lead to plug overheating or blow-out.
Carburetor mounting bolts, which secure the carburetor to the intake
manifold or cylinder head, are tightened to 7.2 lb-ft. This lower torque
value prevents distortion of the carburetor flange and potential air
leaks, which would disrupt the air-fuel mixture and cause poor engine
performance.
The oil filter should be tightened to 13 lb-ft. While many installations
rely on a hand-tightening method, this specified torque ensures the
filter gasket seals properly against the engine block to prevent oil
leaks under operating pressure. It also ensures the filter is
sufficiently secure without being overtightened, which could make future
removal difficult or damage the filter seal.
| Boat Applications |
The Evinrude 9.9 HP four-stroke outboard is ideally suited for a wide variety of small watercraft. It is a popular choice as a primary power source for aluminum fishing boats, jon boats, and small inflatable boats (dinghies). Its manageable weight and power output also make it a dependable auxiliary or "kicker" motor for larger sailboats and cruisers, providing reliable trolling or emergency power.
It is also well-suited for propelling canoes and other lightweight vessels where portability and ease of use are paramount. Owners of Catalina 22 and similar trailerable sailboats frequently use this engine size for auxiliary power.
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