CHAPTER 4
Terminals cost literally pennies. Yet a supply of them can save the vessel and all aboard.
A less likely scenario is that the relay which sends power to the starter motor or solenoid has given up the ghost. You can’t repair these and they aren’t easy for an amateur to diagnose, but if you carry a spare and all else fails, they are simple enough to replace.
• Flat battery
When power is switched in to the starter motor, it comes first to an integral solenoid. This is an electrical switch that opens the floodgates to the massive current needed to turn the engine. When the solenoid ‘throws’, the big power is released to the starter motor itself. The sad, dying grunt of one of these trying to start an engine on a flat battery is unmistakable. So is the final expiring click of a solenoid that isn’t powered up enough to activate itself, let alone the main unit. Either of these noises confirms that power is getting to where it’s needed, but that there isn’t enough of it.
The question as to why the battery is flat is important, but it can wait for now. If you can hand-start the engine, do it. If not, the next thing is to find some volts from somewhere else.
Single-battery boats – Where the boat has only one battery and the multimeter shows the voltage has gone down the plughole, you’re a dead duck. You’ll have to find either a jump start from another boat, or a source of mains power to plug in your handy battery charger. Even if you have more than one battery, every boat should still carry a set of heavy duty jump leads. You may only use them once in a decade, but when the day finally comes, nothing else will do. Here’s the process for jump-starting safely: • Turn off all electrics, including anything that might be plugged into a charger. Visually check that your battery casing is not cracked. If it is, DO NOT attempt to jump-
start it. It may burst, with consequences too awful to contemplate.
• Check the voltage on the donor battery. It should be well above the 12.0-volt margin.
• Connect the positive terminal of the flat battery to the positive terminal on the donor battery using the red jump lead (1).
• Connect one end of the black jump lead to the negative terminal on the donor battery (2). The other end should be clipped onto a hefty bright metal fitting on the block of the engine suffering the flat battery (3). Don’t use a painted or oily fitting. A big nut is good. Hooking up the two negative battery terminals works well but it may spark, which in extreme circumstances can be an explosion hazard. Do it only if you can’t get a good earth the other way.
• Activate your starter motor. Assuming the engine is healthy and the donor battery is good, it should fire up promptly.
• If it doesn’t, check connections (there may be a few small sparks as you do this – no problem) and try again.
• With the engine now running, disconnect as follows: Remove the black lead from your engine block, then the other end from the donor battery. Take the red cable off the donor battery then from your own.
• Keep your engine running for at least half an hour to charge your battery. The longer the better.
Jump-starting
(3)
(2)
Donor battery Flat battery (1)
MANUAL OF SEAMANSHIP | 37
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