Johnson Service Bulletin SB-813 - Alternator Equipped Engines

November 30, 1960

Bulletin No. SB-813 Electrical System

SUBJECT: ALTERNATOR EQUIPPED ENGINES.

Introduction of the alternator equipped 75 H.P. engine brings with it some new factors to be considered during installation, demonstration and servicing of Johnson outboard engines.

The alternator in itself has proven to be quite trouble free and very versatile. However, as with most of the new developments of today, although it is rugged, it is also quite sensitive. It will not function properly, and may even fail, if carelessly installed. Here is a brief outline of what you can expect from these new alternator equipped engines and how to handle them for maximum trouble free operation.

1. IGNITION: a. BATTERY: The ignition on these engines is battery operated, similar to an automobile. Adhere to the battery recommendations which remain the same as for our other electric starting engines. b. IGNITION "ON" LIGHT: An ignition indicator light goes on when the ignition switch is turned on. Mount this light in the dashboard so it can be easily seen, even in sunlight. c. COIL: There is a resistance wire (tagged) attached to the ignition coil. This wire becomes very hot during engine operation. This is normal. DO NOT SHORTEN, LENGTHEN, OR SUBSTITUTE THIS WIRE. Use only a regular, service replacement resistance wire if required!

2. ALTERNATOR (a.c. generator) a. OUTPUT: The alternator is an AC generator electronically controlled by a transistorized regulator. It will provide approximately 5 amps charging current at 500-600 r.p.m. It will provide a maximum of 20 amps at engine speeds over 2500 r.p.m. This output is over and above the requirements for engine operation. b. The alternator has the capacity to operate several electrical accessories. (More sales for you of these electrical units.) c. CURRENT DRAW (discharge): The current draw (discharge) of the alternator with the ignition switch on and the engine not running is 4 to 5 amps (registered on the ammeter). Under the same condition the ignition coil will draw the same current. Therefore, with the breaker points open, the current draw will be 5 amps; with the points closed it can go up to 10 amps. This, of course, is with no other accessories on. You can see that if the ignition switch is left on for a long period with the engine not running, the battery can be run down. When the engine is running, the alternator still requires about 5 amps while the coil requires only 1 amp or less. d. SERVICING: When ever servicing an alternator unit, be sure to have the complete electrical system available, if possible. This may mean either service calls on the boat, or having the boat brought to your shop. Testing procedures are being developed now. With proper equipment they can be performed on the boat or in the shop.

WAUKEGAN, ILLINOIS

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3. ELECTRICAL CONNECTIONS: (very important) a. The importance of good electrical connections cannot be overemphasized. Anything that will create high resistance, such as loose screws and/or corroded terminals, can cause trouble! This should be stressed in your service shop and to the customer as preventive maintenance. b. BATTERY CABLE CONNECTIONS: Reversed polarity (battery cable connections) can cause immediate damage to the rectifier diodes. There are four diodes and it is possible to burn all four if the polarity is reversed. These diodes have a list price of $6.00 each. Damage due to reversed polarity is readily recognizable by experienced personnel and is not considered a failure due to defective parts or workmanship. Be very careful when connecting the battery leads from the junction box to the battery. The leads are tagged and the two terminals are of different sizes to assist in preventing any error.

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4. JUNCTION BOX: a. VENTILATION & INSTALLATION: When operating at full output, the junction box assembly gets very hot. It is important that the box be properly mounted and adequately ventilated. The box must always be mounted upright and within 15° from vertical. This provides the proper "chimney" effect thru the box for adequate cooling. This is very important for extending the life of the transistor in the regulator! b. ACCESSORY CONNECTIONS: The ammeter and switch are calibrated into the regulating circuit; therefore, all accessories have to be connected to the accessory terminals on the junction box. c. SERVICING: Always remove the battery leads before removing the junction box cover. Do not make or break connections while engine is running. Test procedures are being developed which may require operation of the engine with the junction box cover off. This is the only time the battery should be connected after the junction box cover is removed for inspection or maintenance. d. FUSE REPLACEMENTS: Be very careful when replacing fuses. Use only exact replacements. When working with the 60 amp. fuse or any components attached to it, be sure to replace everything in the correct sequence (see Parts Book) to insure proper operation of the filter condenser. If the parts are in- correctly replaced and the 60 amp. fuse blows, it is possible to damage the rectifier diodes.

5. TACHOMETERS: Tachometer leads are provided for operating a battery ignition type tachometer. A magneto type tachometer will not work with this engine.

6. EMERGENCY STARTING: a. DISCHARGED BATTERY: The engine has provisions for manual starting, using an emergency rope starter. The voltage requirements for ignition is so low that the engine can be easily started by hand even though the electric starter motor will not even engage. If the switch has been left on for a period of time and the starter will not operate, very often by turning the ignition OFF and letting the battery recuperate for 15 or 30 minutes, hand starting can be accomplished. CAUTION: There is no safety interlock when hand starting. Be sure engine is in neutral!

7. TANK TESTING AND DEMONSTRATIONS: Since the operation of these engines is dependent on the complete electrical system, it is necessary to have a junction box assembly for tank testing and boat demonstrations. You may find it most convenient to mount one unit on a board so that it can be moved from tank to boat for testing or demonstration.

To summarize, the main source of trouble is slipshod, haphazard workmanship in the initial installation. The alternator is rugged and efficient, has few moving parts subject to wear, provides high output at low engine speeds, and allows the owner to operate many more electrical accessories. Impress your customers with its few peculiarities and the need for proper maintenance and you will find the alternator a basically trouble free unit.

JOHNSON MOTORS

W. W. DeWees Service Department

WWD:eb NOTE: Post on your V4 index - 75 H.P.