This repair manual covers all 1977-1989 Mariner outboard motors 45-220 HP. 3-, 4-, and 6-cylinder in-line motors, plus V6 and V6 with electronic fuel injection (EFI), 2-stroke engines.
Book Excerpt: 1977-1989 Mariner Outboard Repair Manual 45-220 HP, 3, 4, and 6-Cylinder 2-Stroke Models ENGINE TUNING

TUNE-UP SEQUENCE During a major tune-up, a definite sequence of service work should be followed to return the engine to the maximum performance desired. This type of work should not be confused with attempting to locate problem areas of "why" the engine is not performing satisfactorily. This work is classified as "trouble shooting". In many cases, these two areas will overlap, because many times a minor or major tune-up will correct the malfunction and return the system to normal operation. The following list is a suggested sequence of tasks to perform during the tune-up service work. The tasks are merely listed here. Generally procedures are given in subsequent sections of this chapter. For more detailed instructions, see the referenced chapter.

1. Perform a compression check of each cylinder. See Chapter 6.
2. Inspect the spark plugs to determine their condition. Test for adequate spark at the plug. See Chapter 6.
3. Start the engine in a body of water and check the water flow through the powerhead. See Chapter 11.
4. Check the gear oil in the lower unit. See Chapter 11.
5. Check the carburetor adjustments and the need for an overhaul. See Chapter 4.
6. Check the fuel pump for adequate performance and delivery. See Chapter 4.
7. Make a general inspection of the ignition system. See Chapter 6.
8. Test the cranking motor and the solenoid. See Chapter 9.
9. Check the internal wiring.
10. Check the timing and synchronization. See Chapter 7.

POWERHEAD

TIMING The exact time of spark plug firing depends on the engine speed. At low speed the spark is retarded, fires later than when the piston is at or beyond top dead center. Engine timing is built into the unit at the factory. At high speed, the spark is advanced, fires earlier than when the piston is at top dead center. On some late models and larger engines, the timing can be changed in the field to meet advance and retard factory specification.
SUMMARY More than one phase of the cycle occurs simultaneously during operation of a two-cycle engine. On the downward stroke, power occurs above the piston while the ports are closed. When the parts open, exhaust begins and intake follows. Below the piston, fresh air-fuel mixture is compressed in the crankcase. On the upward stroke, exhaust and intake continue as long as the ports are open. Compression begins when the ports are closed and continues until the spark plug ignites the air-fuel mixture. Below the piston, a fresh air-fuel mixture is drawn into the crankcase ready to be compressed during the next cycle.

COOLING LECTURE

The water circulating in the cooling jacket surrounding the powerhead is controlled by the powerhead operating temperature and subsequently by the water pressure. At powerhead start-up and at low idle speeds, the thermostat is closed. There is no movement of water until the temperature in the cooling jacket reaches 145 degrees F. At approximately this temperature the thermostat begins to open allowing fresh cold water from the water pump to circulate through the water jacket. If the cool water reduces the operating temperature of the powerhead below 145 degrees F, the thermostat starts to close and restrict the flow of water. The water remains in the cooling jacket until it reaches the required temperature once more and the cycle repeats itself.

Subject: 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989 Mariner Outboard 45-220 HP, 3, 4, and 6-Cylinder 2-Stroke Models service, maintenance, repair. ISBN-10: 0893300160 | ISBN-13: 9780893300166 | Seloc 1402