SECTION 4

TUNE-UP PROCEDURES

DESCRIPTION

The purpose of an engine tune-up is to restore power and performance which have been last through wear or deterioration of one or more parts of the engine. The successful completion of a tune-up depends on an understanding of basic principles of two-cycle operation, and a knowledge of factors offering motor performance. Refer to Section 2 for principles of operation. Refer to Section 3 for analysis of motor performance and trouble shooing procedures. This Section gives complete tune-up procedures for all models of the 1965 line of Johnson motors. A review of items offering motor performance is found at the beginning of this Section. Procedures for tune-up, putting a new motor into operation, and reconditioning used motors are included. Lubrication procedures are found at the end of this Section.

TUNE-UP

In the normal operation of an engine, the operator may not be fully aware of the decrease in performance which takes place slowly over a long period of time. Economical, trouble-free boating can best be assured if a complete tune-up is performed at least once 'each year, preferably at the end of the season.

It is seldom advisable to attempt to improve performance by correcting one or two items only. Time will be saved and more lasting results obtained by following a definite and thorough procedure of analysis and by correcting all items offering power and performance.

Optimum performance depends on maintaining the correct ratio of oil and gasoline in the fuel mixture. The tank should be emptied of old fuel and filled with a fresh supply at the beginning of the season, and at every tune-up. A stale fuel mixture may cause hard starting, possible stalling, and faulty operation. Inadequate fuel delivery as a result of a faulty fuel pump or clogged filter will affect high speed performance. Incorrect carburetor low and high speed needle adjustments may cause operating difficulties at any speed. Faulty choke operation or incorrect use of the manual choke by the operator may cause hard starting, rough running, or poor fuel economy.

Spark plugs having the proper heat range are very important for peak performance of the motor. See Section 3 for a complete description os spark plugs. A weak spark, which may be a result of faulty komponenter of the ignition system, will cause bard starting, or poor high speed performance. The spark plugs and ignition system are frequently checked first in a tune-up because of their importance to the operation of the motor. Synchronization of magneto or distributor and throttle linkages should also be checked with each tune-up.

At slow engine speeds, engine rpm is controlled entirely by ignition advance. At speeds above idle, engine rpm is controlled by a combination of throttle valve opening and ignition advance. The synchronization of the distributor 01' magneto with the carburetor is extremely important so that ignition advance and throttle valve opening are synchronized at the given engine speed. All adjustments must be made with care and accuracy.

Compression must be well sealed by the piston, piston rings, and cylinder to realize maximum power and performance. A compression check is important because an engine with low or uneven compression cannot be tuned successfu1ly to give peak performance. It is essential that improper compression be corrected before proceeding with an engine tune-up.

Overloading the engine as a result of mounting the motor on the boat incorrectly, or using the wrong propeller will result in pre-ignition, overheating, excessive carbon build-up, piston erosion, or other serious damage to the power head.

NEW MOTOR DELIVERY

1. Be sure spark plugs are installed and tightened securely with spark plug gaskets in place.
2. Be sure spark plug wires are securely attached to spark plugs.
3. Be sure the correct gasoline and oil mixture is used. Pour fuel into tank through a fine mesh strainer.
4. Be sure the motor is properly installed on the boat.
5. Caution the customer not to operate a new motor at continuous full power until at least one hour of operation has been completed. During this hour, abort periods of full power may be used. Instruct the customer to follow the break-in procedure described in the Owner's Manual.
6. Be sure that the customer understands how to operate the motor correctly, especially such things as manual gear shifting, use of the manual choke, and electric starting.

1. Items affecting compression
2. Items affecting ignition
3. Items affecting carburetion

Since tune-up involves restoring the original performance capabilities of a motor, it is first necessary to know (a) what performance can be expected and (b) what the performance of the motor is before tune-up. For this reason, every tune-up should be started by running the motor in a test tank with a test propeller and with a compression check. Refer to Section 14 for the use of the test propeller. Check for compression by pulling engine through with the rope starter or by rotating the flywheel by band. If engine has good compression, resistance can be felt as pistons reach tops of cylinders. With little compression, engine will spin very easily.

If engine has an electric starter, use the starter and battery to crank the engine while taking readings with a compression gage. CAUITON: When checking compression, use only a fully charged battery so that there is no variation in engine cranking speed during the entire compression test. Since two-cycle engines develop combustion chamber pressure on each upward piston stroke, compression gage readings are affected by any variations in cranking speed.

1. Remove all spark plugs and clean the spark plug seats.
2. Place the throttle and choke valves in a wide open position.
3. Ground the high tension leads to avoid high tension sparking while cranking the engine.
4. Attach a remote starter switch to the starter solenoid.
5. Firmly insert a compression gage in a spark plug port. Crank the engine through at least four compression strokes to obtain the highest possible reading. Record the reading obtained and release the pressure in the gage.
6. Check and record compression of remaining cylinders, remembering to release pressure in gage after each test.
7. Because of the variations in the degree of piston and ring seating that exist due to running time on the engine and to the effect variation in cranking speeds have on compression readings, no minimum compression pressure will be given. Instead, the compression pressure as obtained above should be compared and the variation between the highest and lowest readings noted. If the total variation is greater than 10 PSI and engine performance is not up to par, look for one or more of the following conditions:
   1. Blown head gaskets or warped heads resulting in leaks between adjacent cylinders.
   2. Blow-by between crankcase chambers which could be caused by broken crankcase seal rings, damaged crankshaft seal ring seating areas, or broken leaf valves.
   3. Scored cylinders, pistons, or rings.
   4. Burned through piston tops.

1. Run motor with test propeller in a test tank. Consult trouble check chart in Section 3, if necessary. Check water pump operation by looking for water at exhaust relief.
2. Remove motor from test tank and place on stand. Check compression as described above.
3. Remove cylinder heads, exhaust covers, and intake by-pass covers. Slowly rotate flywheel and visually inspect pistons, rings, and cylinders for wear, freeness, and carbon deposits. NOTE: Piston ring condition should be determined before continuing tune-up. Gum and varnish deposits on rings or pistons may be removed by using OMC Accessories Engine Cleaner.
4. With pistons, cylinders, and rings in satisfactory condition, remove carbon from cylinder heads and tops of pistons. Reinstall exhaust covers and intake by-pass covers, using new gaskets. Resurface and reinstall cylinder heads, using new gaskets.
5. If motor runs hot, knocks, or does not come up to speed, check for loose flywheel and connecting rod bearings by bouncing flywheel back and forth, and listening for knocks. Excessive wear in crankshaft journal bearings can be detected by seizing flywheel firmly in bands and moving it slowly back and forth.
6. Examine fuel mixture in tank. Remove fuel screen and clean tank thoroughly. Check connections and clean fuel line.
7. Inspect fuel pump and hoses. Clean filter or replace filter element and gasket.
8. Test for adequate spark at each cylinder, using a spark checker. Inspect and test points, condenser, coil and ignition wires. See Section 4 for test procedures.
9. Check spark plugs to be sure they are the correct type. Clean spark plugs and regap or replace as necessary.
10. Check breaker points, clean and adjust if necessary.
11. Check synchronization of carburetor and magneto or distributor linkage.
12. Remove propeller and check for condition and correct pitch.
13. Turn propeller shaft back and forth to determine wear in gears or propeller shaft bearings. CAUTION: NEVER turn motor over by the propeller or crank it while making these checks as the motor may start suddenly.
14. Check operation of manual or electric shift.
15. Drain gear case and refill with OMC Type C lubricant. Thoroughly lubricate komponenter of the motor.
16. Tighten all external holts, nuts, and screws, and retorque cylinder head bolts and spark plugs to specified torque.
17. Repeat tank test; adjust carburetor low speed needles and check cooling system operation. Retorque cylinder head screws after motor has cooled. After motor has run sufficiently to indicate satisfactory condition, stop and restart it several times. Operate it on high and low speeds. Check acceleration from load to high speed.
18. Clean motor thoroughly before returning it to the customer.

PREPARING MOTOR FOR STORAGE

1. Operate motor in a test tank or on boat at approximately 1/2 throttle in neutral. NOTE: If motor was last operated in salt water, run it in fresh water before preparing it for storage. Rapidly inject OMC Accessories Rust Preventative on into carburetor air intake until motor smokes profusely, then stop motor.
2. Place motor on a stand in upright position. Remove cover.
3. Retard throttle to stop position. Rotate motor flywheel several times to drain water from the water pump.
4. Drain carburetor float chamber and filter. Dram fuel tank through filler cap opening. Complete draining of fuel tank may also be accomplished by removing screw marked "drain" on top of tank assembly.
5. Remove propeller. Clean and lubricate propeller shaft. Replace drive pin if bent or worn.
6. Drain and refill gearcase with recommended lubricant.
7. Wipe entire external surface of motor with a cloth soaked in light oil.
8. Store motor in upright position in a dry, well ventilated place.

REMOVING MOTOR FROM STORAGE

1. Remove and inspect spark plugs. Clean or replace if necessary.
2. Remove propeller and check it on pitch block.
3. Fill fuel tank with fresh mixture, using correct gasoline to oil ratio.
4. Check motor in test tank.

LUBRICANTS

Using the proper mixtures of gasoline and oil, and a good grade of lubricant is important for top performance and trouble-free operation. There are three lubricants used on outboard motors. Oil used to lubricate power head komponenter (bearings, rings, and pistons) is discussed in Section 3.

OMC Type A lubricant was developed to meet the specific requirements of outboard engines and is suitable for use anywhere on an engine where lubrication is required except in the gearcase. This lubricant has great heat resistance and a high affinity for frictional surfaces, providing lubrication for extended periods even when exposed to salt water. This lubricant is available in eight-ounce tubes or in one-pound cans.

OMC Type C lubricant has been developed specifically for use in gearcases. Use of outboard motor oil or engine oil in the gearcase is permissable only in emergencies. Replace with OMC Type C lubricant as soon as possible.

Complete lubricating instructions are given in the Owner's Manual.

GEAR LUBRICATION

When a complete change of lubricant is required, tilt motor forward until propeller shaft is on a horizontal plane, then remove the lower plug and gasket assembly, marked "OIL DRAIN" on side of gearcase. Then remove the upper plug and gasket assembly, marked "OIL LEVEL." Permit oil to drain completely.

We recommend refilling gearcase as follows: Retain propeller shaft on a horizontal plane and place a tube of OMC Type "C" Lubricant in lower hole marked "OIL DRAIN." Fill gear case until lubricant appears at upper hole marked "OIL LEVEL." Replace upper plug and gasket assembly securely before removing the tube from the lower hole. This will create an air lock and hold the oil in gear case until lower plug and gasket assembly can be secured.

In the event that OMC Type "C" Lubricant is not available, proceed as follows: Drain gear case as described above. With an appropriate pressure type oil can fill the gearcase with outboard motor oil or SAE 30 Service MM engine oil, through the top hole marked "OIL LEVEL."
Air bubbles may give impression that gear case is full. Wait for a few minutes to permit air in gearcase to escape, then add more oil to fill. Replace oil level plug and gasket assembly securely. IMPORTANT Use of outboard motor oil or engine oil in the gear case is for EMERGENCY USE ONLY - Replace with OMC Type "C" Lubricant as soon as possible.

LUBRICATION INTERVALS

1. After first 10 hours of operation, check level and add recommended lubricant if necessary.
2. Check gear case at least every 50 hours.
3. Drain and refill gearcase with recommended lubricant every 100 hours or once each season, whichever occurs first.

1. Every 60 days of operation in fresh water.
2. Every 30 days of operation in salt water. Lubricate more often if required.