POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS Finally, connect the meter as shown in figure 8-7d on page 131 with one probe connected to the body of the starter motor (scrape away a little paint to be sure of a good contact) and the other probe connected to the negative terminal on the battery. Turn the key to start. Your voltage reading should be less than 0.3 volt. If the reading is higher, either a connection is bad at the engine or at the negative battery post, or the cable is undersized. (It should also be the same size as the main battery cables.) This test will work with any starter circuit, inboard or outboard, and the values for allowable voltage drop given here apply to all systems using a 12-volt power, regardless of engine size. Also, you may notice that the total voltage drop may exceed the 3 percent mentioned earlier in this book. Oddly enough, the total individual voltage drops may fall somewhere between the 3 and 10 percent limits discussed. I have always felt that the 3 percent maximum is most important for a starter-motor circuit, meaning that the total voltage drop would be no more than 0.36 volt for the entire circuit. Having said that, I can tell you that engine-service manuals consistently use a 0.2-volt maximum drop for all the connections and parts up to the starter motor, and 0.3 volt back to the battery as the acceptable limit; this gives a maximum of 0.5 volt. The truth is, a well-done factory circuit will give voltage readings well below the 3 percent tolerance, and I prefer to use that figure for my own criterion. I mention the 0.2- and 0.3-volt specifications here only because I know you’ll run into them if you follow your service manual as you should, when doing these tests.
Testing the Neutral-Safety Switch If your boat has remote engine controls, with the shift lever and ignition switch at the helm, the neutral-safety switch is located inside the control unit. Therefore, you should never attempt to diagnose problems with this switch without the aid of the workshop manual for your engine and control unit. There are just too many variables in wire colorcoding and control-unit disassembly procedures 132
to cover them all here. In fact, unless you’re fairly confident as a mechanic, you should never remove or attempt to disassemble the remote-control unit. It’s full of spring-loaded levers, shims, and cable attachments that are critical in their placement and function. So beware! However, it’s quite easy to check all wiring and parts affected by the neutral-safety switch, enabling you to consult intelligently about the problem with your mechanic. Your neutral-safety switch is electrically connected to both your ignition switch and the starter solenoid. When you shift into neutral, the switch should close, completing the circuit between the ignition switch and the terminal marked connection A, shown in figure 8-7a on page 130. The wire on this terminal connects the solenoid to the ignition switch and should be identified in your wiring diagram. The quick check to see if the switch is functioning is to look for a 12-volt reading at this terminal with the key on start. Simply connect your meter with the black probe to ground and the red probe to this terminal, and have someone shift into neutral and turn the key to start. If you get no reading when the key is turned to start, the problem is probably within the control unit, but not necessarily. There could be corrosion at the remote-control master plug, or there could be a break in the wire connecting the plug assembly to the back of the boat. Using your wiring diagram as a guide, identify this solenoid feed wire. Next, disconnect the wire from the solenoid and identify which terminal it goes to in the plug assembly. With your multimeter set to the low-ohms scale, check for continuity between these two points. (Using your alligator clips, you may want to make an extended jumper lead to one of the test leads from your meter, depending on the distance between the plug assembly and the solenoid.) You should get a reading of nearly zero ohms if this wire is intact from the plug to the engine. If you get a high reading or a reading of infinity, there is a break in the wire or a corroded connection between the plug and the engine. In some cases, this will mean replacing the extension harness as a unit. If the wire from the control unit to the solenoid
