POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS
Fig. 7-11a. Surface gap and traditional spark plugs.
Fig. 7-11b. A spark-plug gapping tool.
duces electrical current. The more windings, the more current is produced. As the secondary voltage leaves the center tower of the ignition coil, it travels through the spark-plug wire (the high-tension lead), which is heavily insulated and designed to carry high voltage. If all is well, the high voltage will jump the gap between the center electrode of the spark plug and the ground electrode, completing a circuit to ground. On larger engines with surface-gap plugs, the side of the spark plug is the ground electrode. Figure 7-11a shows both plug types. Figure 7-11b shows a spark-gapping tool being used to adjust the electrode gap.
them will follow a little later in this chapter.
Engine Stop Control Last, but certainly not least, is the stop control—the device you use to shut off your engine by disabling your ignition system. Depending on the engine, the stop control might be activated by a simple stop button or, on larger engines, by a key switch. On newer engines, you’ll find an emergency-stop button with an overboard clip and lanyard wired directly to your system’s CDI unit. When the lanyard is pulled, the clip is yanked out of the stop button. This creates a momentary short circuit inside the CDI unit that diverts the voltage intended for the high-tension coils directly to ground and shuts off the ignition long enough to stop the engine. These stop circuits can cause a lot of problems, and procedures for testing 112
Outboard and PWC Ignition Tests The first step with all electrical-circuit testing is to carefully use your eyes. Look for the obvious! Whenever a problem develops with any engine or system that has been regularly maintained, troubles are almost always due to some minor oversight and are easily solved. Check all the wiring for any loose connections on your engine. Look for signs of corrosion on terminals and connectors. Check for any broken or frayed wires. Make certain the problem is not something as silly as a blown fuse. Any of these things can be the cause of ignition problems, and they can be quickly fixed with basic tools.
Testing for Spark As with the inboard systems, the first step in troubleshooting your ignition system is to verify that you’re getting spark. However, with outboard and PWC systems you need to check each cylinder because each cylinder has its own high-tension coil, and partial system failures of one cylinder are not uncommon. When checking the coils, it’s extremely important that you check for any fuel leaks and make certain that all fuel line fittings and connections are secure. It is a good idea to create some shade near the
