Part 2 – Solving the problem
Electrics, including starter motors, alternators and wiring
Avoiding problems with these items is often a maintenance issue, although wiring should be visually inspected as part of the daily checks for obvious problems. Looking at the tension and condition of the alternator and water pump drive belts will also identify any problem with these well before there’s a risk of failure.
If you have an older engine and are cruising longer distances, a spare set of brushes for starter motor and alternator may be a good precaution. Beyond that, having ample power to start the engine is an important factor, which largely boils down to good battery management.
If faced with a lack of power there are a number of actions that may get the engine running again. If your engine is fitted with decompression levers for use with hand starting, then lifting these as you spin the engine on the starter motor will hugely reduce the electrical power needed.
If not, the first stage is to give the batteries their maximum chance of recovering some charge. If possible turn off all electrics for 10-15 minutes – the voltage will rise a little during this time. If power is not being drawn off elsewhere the next time you try to start you might just be lucky.
Another issue could be a loose connection in the high load wiring to the starter motor. A quick check for excessively hot contacts will give an indication to this problem. To fix it, dismantle the terminal, clean contacts thoroughly, reassemble and try again.
Fuel system
Most small marine diesels are so simple that, other than a cooling system, they require only a supply of air and clean diesel to operate. The most common problems are with dirt in the fuel, which slowly blocks filters until the point is reached that insufficient fuel can get past, or air is sucked into the system instead.
It’s therefore always worth carrying spare filters – normally two types are required, for the pre-filter closest to the fuel tank, plus the second unit that’s mounted on the engine itself.
Changing these filters – and then bleeding the air out of the fuel system – is a relatively simple operation.
But trying to figure out how to do so for the first time at sea is not a good move. It makes sense on the first occasion to do this it as part of basic engine servicing. It’s a great confidence boost the first time you successfully manage it on your own boat.
Overheating
Most problems stem from the raw (sea) water side of the system. At the very simplest a plastic bag or sheeting may be sucked across the inlet through-hull fitting, blocking the water flow. This can be hard to diagnose, as the plastic may float away when the engine is turned off.
Alternatively, debris can be drawn into the filter. If so, cleaning the filter is usually all that’s needed to get the engine working again. But… the flexible rubber impeller that pumps the sea water around that side of the system relies on a supply of water for lubrication. If the engine is run without cooling water circulating for more than a minute or two the impeller may overheat, or blades may break off. If this has happened the impeller needs to be replaced – and any broken pieces retrieved so they don’t block waterways.
Impellers have a limited service life, even on engines that only clock up a handful of hours each year. If you flex the blades of an impeller that’s at the end of its useful life tell-tale cracks can often be seen at the base of the vanes.
Fouled propellers
I’m often astonished by the number of boats where the engine is started and forward power engaged while the headsail sheets are flailing around. It’s a quick job to tidy the sheet tails such that they can’t create embarrassing problems later. This of course also applies to spinnaker gear and halyards that are handled at the mast.
Even if your boat’s own lines are kept impeccably tidy, there’s still plenty of scope to encounter floating lines, plastic sheeting and nets in the water, especially in the dark. Prop shaft rope cutters will deal with all but the most stubborn of these and prevent consequential damage caused by the engine and gearbox attempting to continue to rotate while the propeller is jammed in one position.