Maintaining Marine Ignition Systems
Testing Your Stop Switch Your engine, depending its size and the way it’s installed, might have a remote key switch to turn the ignition on and off, or it might have a simple stop button mounted on the engine or steering tiller. In either case, the tool of choice for testing the stop-switch circuit is your multimeter, set to read resistance. You also need the wiring diagram for your engine. If you don’t have a remote-control starter switch, look under the engine cowl where the wiring and cable controls come out of the steering tiller. You should find two wires, one going to ground and the other going to the CDI unit. Verify you have the correct wires by checking your engine-wiring diagram. Next, find a good ground on your engine. Install the emergency-stop clip if your engine has one, and make sure your engine is ready to run. Connect your multimeter’s black probe to ground and the red probe to the plug or to the wire coming from the stop button. If all is well, you’ll get a high (infinity) reading, indicating an open circuit. Any reading showing continuity indicates a defective switch or a short to ground in the wire coming from the switch somewhere inside the tiller handle. In either case you’ll have to replace the assembly. If all appears to be OK to this point, push in the stop button and check your meter. It should indicate continuity with a low reading. Finally, if you have a stop clip, pull it out and observe your meter reading. It should again show a low reading. If pushing the stop button or pulling the emergency clip does not give the desired low ohmmeter reading, the assembly must be replaced. Figure 7-19 shows a typical meter hooked up for these tests. On larger engines with a remote-starter switch, you still check the switch for short circuits to ground; you’ll just have to cover the distance between your engine power head and the key switch. Use your ohmmeter and your engine’s wiring diagram just as before. Identify all the terminals and connections on your key switch by removing the back cover of the control unit to get at the back of the switch. Some manuals show a detailed picture of the plug assembly coming from the back of the switch and identify all
Fig. 7-19. Multimeter tests of an outboard-engine stop circuit.
the terminals and connections. If you can get at the plug in this case, you won’t have to remove the remote-control assembly. If removal and partial disassembly of the remotecontrol assembly are necessary, carefully follow the instructions for opening the control unit. In some cases removal of the central pivoting screw can create quite a mess, and it can be difficult to reassemble. If the remote-control assembly has a key switch separate from the shift control, this central-pivot screw will not be a problem. You can usually access the back of the switch without removing the switch from the panel. Now use your wiring diagram to identify the wire coming from the back of the ignition switch to the ground shut-off at the power pack. As with the smaller engines, this wire will usually terminate at a gang plug under the engine cowl in the harness going to the power pack. Once you find it, disconnect the plug or connection to the remote-control assembly. Now you’re ready for your ohmmeter tests. Check at the engine end first, and, for your multimeter’s safety, be sure your battery is disconnected before doing this test. First, connect the red probe on your ohmmeter to the wire that runs from the ignition switch to the remote-control assembly. Connect the black probe to a good ground. With the ignition key on, you should get a high reading or infinity. If your meter indicates a complete circuit with a resistance reading near zero, 119
