CDI Electronics Outboard Ignition Troubleshooting Guide

90 TROUBLESHOOTING GUIDE - Mercury Troubleshooting Mercury Troubleshooting Mercury One and Two Cylinder Engines 1966-1985 (With 174-3996/ 3 36-3996/336-3962 Stator/Switch Box) WARNING!! DO NOT START AND RUN THIS ENGINE ON A FLUSHING ATTACHMENT OR EAR MUFFS AND ACTIVATE THE STOP CIRCUIT. This system operates with the Orange stop wire normally shorted to ground. When you activate the stop circuit, you open the Orange’s connection to ground. The resulting backlash into the stator may damage the electronics. You must use the choke to stop the engine. In the water, the back pressure from the exhaust will slow the engine quickly enough to prevent damage to the stator. (Note) The insulator blocks used with this stator are very important. You are strongly advised to closely inspect the Brown and White points wires and insulator blocks for cracking or arcing. This system operates at a much higher voltage than the normal systems and what would be acceptable on other systems will cause arcing problems. SERVICE NOTE: These engines require the Orange, Red or Green Ignition coils. The Black or Blue ignition coils use a common ground connection internally for the primary and the secondary side of the coils. This system requires that the primary and the secondary side of the coils be separate as the points drive the negative side of the coil to ground, causing the coil to generate spark on the secondary side. N O SPARK ON ANY CYLINDER: 1. Disconnect the Orange stop wire and connect it to engine ground. Retest. If the ignition system now has spark, the stop circuit has a problem. 2. Disconnect the Brown and White points wires from the ignition coils and connect a jumper wire to the negative side of the coils. Crank the engine and carefully tap the jumper to engine ground, if the coil sparks – check the points and points wires. If it fails to spark, inspect the ignition coil. You should have either a Red, Orange or Green coil with a bare braided ground wire from the backside of the coil. This bare braided ground wire MUST be connected to a clean engine ground. You cannot use a Black or Blue ignition coil. NO SPARK ON ONE CYLINDER: 1. Disconnect the Brown and White points wires from the ignition coils and swap them for a cranking test. Crank the engine over and see if the spark moves to a different coil. If it does, you have a problem in the points, points wire or insulator block for the cylinder not sparking. 2. If the spark remains on the same coil when you swap the points wires and it is the coil where the Green wire is coming from the stator, remove the Green jumper wire. Swap the Green wire coming from the stator from one coil to the other coil. If the spark moves to the other coil, replace the Green jumper wire connecting the two coils. 3. Check the ignition coil. You should have approximately 1,000 (1 K ohm) of resistance from the spark plug wire to engine ground using the Orange coil and 600 ohms for the Green coil. 4. Inspect the ignition coils. You should have either a Red, Orange or Green coil with a bare braided ground wire from the backside of the coil. This bare braided ground wire MUST be connected to a clean engine ground. You cannot use a Black or Blue ignition coil.