Outboard starting problems are unfortunately very common, in particular after winter, and many boats are not properly stored. When the key switch is turned on, a control voltage is supplied from the battery to the starter motor solenoid, and the ignition control (CDI unit or Power pack) system. This may be interlocked with a neutral safety switch and the stop circuit. When the solenoid closes, current is supplied to the starter motor which then rotates and engages. The engine rotates and the charging coil or magneto generates a voltage and supplies this to the ignition module. This is rectified to DC and stored in a capacitor (also called a condenser). A second trigger or pulsar coil generates a smaller voltage and feeds this to the ignition module to time or synchronize the spark. This triggers an electronic switch which then releases the stored charge within the capacitor. The output feeds the primary side of the ignition coil. The secondary side of the coil transforms the voltage to a high voltage up to 50,000 volts. This high voltage goes to the spark plugs. The plugs spark to ignite the fuel and the expanding gases force the piston downwards.
For all outboard starting problems the first question is whether your battery is fully charged. If your battery has sat for weeks and months without being charged then there is a high probability the battery is partially or fully discharged. If this has been a frequent situation over a couple of seasons then the battery has probably got plate sulfation and a permanent loss of capacity. In other words your Cold Cranking Amps (CCA) is much lower and is incapable of turning the engine over. How much battery capacity is required to start outboards? The answer is to install the outboard manufacturers’ minimum recommendation, and a good baseline is up to 50 HP – 450 CCA; up to 120 HP – 500 CCA and up to 350 HP – 600 CCA. If you use the battery for other equipment then you will have to factor that in to the capacity calculations.
If your battery is new, well charged, has full capacity availability and you still can’t get the outboard motor to turn over, then you should check and clean the battery terminals. They should be bright, clean and tight. The starter motor develops the high torque that is required to turn over the engine against the high cylinder compression. The most common causes of starter motor problems are bad connections causing voltage drop. If the starter motor grinds over slowly or the solenoid clicks away without any starter rotation, check the main positive and the negative circuit connections. The main connections are those heavy cables that come from the battery and terminate on the outboard engine. Check that all wiring and plugs are properly installed and are not full of water or loose connections. Check that the electronic control module ground wires are attached and secure. Faults are often typified by reduced engine speeds and a failure to start.
Now the most simple things can cause you outboard starting problems. Absolutely the first things you should check are that the neutral safety switch is closed because the motor is set in Neutral. Also check that the safety stop circuit lanyard if fitted is also closed and in correct position. About stop and neutral position circuits. The stop circuit within multi-position ignition switches or in lanyard type emergency stop switches places a short circuit in the ignition system to stop the engine. They are a constant cause of problems and start failures. In normal operation the contacts are open, and close to shutdown. Some engines may have a tilt-stop switch that activates when the engine is tilted too far up, a common scenario when fishing in shallows. If the engine control is not in neutral position the engine will not start. In many cases a faulty switch or a failure to activate will be the cause of non-starting. The neutral position switches within throttle controls can work loose or be out of adjustment or just mechanically fail. Move the throttle forward and reverse in and out of the detent center position. More great information at fishing and boats.