The Starter System Part Il Editor’s Note: The following information is an excerpt from the ARCO Electrical Technical Manual. Many thanks to this Pensacola, FL- based marine specialist for sharing this valuable resource. Testing the Starter Once the battery is determined to be in good working condition, always test the voltage at the starter regardless of how well the engine turns over. A starter must have at least 9.5 volts terminal voltage under load to operate properly. Other than water damage, low voltage is the number one culprit to a starter’s life expectancy. Low voltage causes excessive heat to build up in the starter. It can also cause the contacts in the solenoid switch to weld together, in which case the end result will be a blown apart starter. Low voltage will also cause a heavy load on the battery and charging system. Connect the positive voltmeter lead to the starter terminal where the battery cable is attached. (See Figure 1.) Connect the negative voltmeter lead to the starter case making sure you have good contact with the metal. This will ensure that the positive and negative circuits will be tested. TO 5S I = Figure 2 the negative voltmeter lead to the nega- tive post of the battery, not to the battery cable end. Connect the positive voltmeter lead to the starter case, being sure to make metal contact. Perform this test in the same manner as with the positive bat- tery cable. Testing the Solenoid Switch Voltage Many times the voltage supply to the starter solenoid is overlooked. Due to the long lengths of wiring from the key switch to the solenoid on marine appli- cations, severe voltage drops will occur in this circuit after a period of time. Even though the starter may seem to be working OK, low voltage to the switch circuit can cause intermittent operation of the solenoid contacts and shorten the life of the solenoid and starter motor. Connect the voltmeter as shown in Figure 1 Crank the engine for about 10 seconds while observing the voltage reading. A reading of 9.5 volts or more would indicate there is sufficient voltage being supplied to the starter to operate properly. If the starter does not function like it should, chances are the starter is defective or the engine has a problem, causing it to be difficult to turn. Try turning the engine over by hand. A voltage reading below 9.5 volts would indicate a voltage loss between the battery and the starter. Let’s say, for example, we had a reading of 10 volts at the battery, while cranking the engine, and we had a reading of 8.0 volts at the starter terminal. This would indicate there is a 2 volt drop in the circuit. The maximum drop allowed in the starting circuit is .5 volts. Corroded battery cables, dirty connections, or insufficient wire size would be the problem here. This could be any connection in the positive or negative circuit. The Voltage Drop Locating the voltage drop is done by a very simple test. This test should be done anywhere a voltage drop is indi- cated. To test the positive battery cable, connect the positive voltmeter lead to the positive post of the battery, not to the battery cable end. Connect the negative lead to the starter terminal where the battery cable is attached. (See Figure 2.) Crank the engine while observing the voltmeter. The reading should not exceed .25 volts. Make sure you remove at least one voltmeter lead before the starter motor is turned off. The starter motor can sometimes generate a spike voltage and damage the voltmeter. If the reading is over .25 volts, excessive resistance is occurring in that cable. To test the negative battery cable, connect Figure 3, page 7 and crank the engine while observing the meter. The voltage reading at this terminal should read at least 9.5 volts. If the voltage is below 9.5 a simple cure is to install a slave solenoid. AFTER SLAVE SOLENOID INSTALLED 12 GAMINIMUM WIRE SIZE BATTERY 1. Mount the slave solenoid as close to the starter as possible. Do not mount the solenoid on the engine. 2. Remove the original wire that is attached to the switch terminal on the starter solenoid. 3. Attach this wire to one of the small terminals of the slave solenoid. 4. Install a ground wire to the remain- ing small terminal of the slave solenoid. 5. Install a 12 gauge wire from the switch terminal of the starter sole- noid to one of the large posts on the slave solenoid. 6. Install a 12 gauge wire from the battery post of the starter solenoid to the remaining large post on the slave solenoid. Noisy Starters and Broken Housings A very common misunderstanding among mechanics is that broken starter housings are due to a defective or TO ACCESSORIES ring gear can wear after a period of time or if the starter is engaged into the ring gear with the engine running. Points to Remember * Starters must have a minimum of 9.5 volts to operate properly. * Always start troubleshooting at the battery first. * Low voltage will destroy a starter. * Never strike a permanent magnet motor with a _ ha