Evinrude Johnson Outboard Repair Manual 2-40 HP 1973-1990

• 2 HP, 2.5 HP
• 3 HP
• 4 HP, Excel 4, Ultra 4, 4 HP Deluxe, 4.5 HP
• 5 HP
• 6 HP
• 7.5 HP
• 8 HP
• 9.5 HP, 9.9 HP
• 15 HP, 18 HP
• 20 HP, 25 HP, 28 HP
• 30 HP, 35 HP
• 40 HP
• Electrics

This chapter contains removal, overhaul, installation and adjustment procedures for fuel pumps, carburetors, fuel tanks and connecting lines used with the Johnson and Evinrude outboards covered in this book. Table 1 is at the end of the chapter.

Johnson and Evinrude outboards equipped with an integral fuel tank use a gravity flow fuel system and require no fuel pump.

The diaphragm-type fuel pump used on models with a remote fuel tank operates by crankcase pressure.

Since this type of fuel pump cannot create sufficient pressure to draw fuel from the tank during cranking, fuel is transferred to the carburetor for starting by operating the primer bulb installed in the fuel line.

Pressure pulsations created by movement of the pistons reach the fuel pump through a passageway between the crankcase and pump.

Upward piston motion creates a low pressure on the pump diaphragm. This low pressure opens the inlet check valve in the pump, drawing fuel from the line into the pump. At the same time, the low pressure draws the air-fuel mixture from the carburetor into the crankcase.

Downward piston motion creates a high pressure on the pump diaphragm. This pressure closes the inlet check valve and opens the outlet check valve, forcing the fuel into the carburetor and drawing the air-fuel mixture from the crankcase into the cylinder for combustion.

Figure 1 shows the operational sequence of a typical Johnson and Evinrude outboard fuel pump.

Johnson and Evinrude fuel pumps are self-contained, remote assemblies. Fuel pump shape and size differs according to engine size.

The square pump shown in Figure 2 is used on 4-15 hp engines. Figure 3 shows the one used on 18 hp and larger models.

The design of both pump styles is extremely simple and reliable in operation. Diaphragm failures are the most common problem, although the use of dirty or improper fuel-oil mixtures can cause check valve problems.

The fuel pump is serviced as an assembly: if defective, replace the entire unit.

• General information
• Tools and techniques
• Troubleshooting
• Lubrication, maintenance and tune-up
• Engine synchronization and linkage adjustments
• Fuel system
• Electrical systems
• Power head
• Gearcase
• Automatic rewind starters
• Electric motors
• Wiring diagrams