Fix your engine at sea
Rupert Holmes offers tips on avoiding engine failure Ð and what to do if it does happen...
Tips on avoiding engine failure and what to do if it happens
Today’s marine engines are generally much more reliable than those of a generation ago, but they are still far from being immune to breakdown. It’s no surprise then that they can be a frequent source of worry, stress and, at times, unscheduled expense when cruising.
Fortunately, boat owners with the right background knowledge, tools and spares stand a good chance of fixing common problems themselves. Even better, there’s
a lot that can be done to stack the odds of preventing engine failure in your favour.
So what are the most common problems? Sea Start compiles statistics from the 2,300 breakdowns they attend each year. Of these roughly 60% are in marina berths or on moorings, with the rest at sea or in anchorages.
Single or twin engine motor boats account for 62% of callouts, with sailing yachts making up 36%. Sea Start fixes almost 90% of problems on site to a level at which “we get people on their way...” according to the company’s founder Nick Eales.
Luckily only 5% of problems are classed as major mechanical failures. This underscores the philosophy that underpins the one day RYA Diesel Engine Maintenance course – that most problems encountered at sea can be sorted relatively easily and without specialist, in-depth mechanical knowledge.
The largest single category of problems, at just over 30% of total callouts, is electrics, including starter motors, alternators and wiring. Fuel system problems are next (21%), followed by overheating (12%). Fouled propellers account for a further 10% of issues and broken drive belts 6%.
I used to think of engine failure as a matter of probability; that sooner or later you would encounter problems if you spend enough time on the water. However, that’s a somewhat passive approach and in reality, assuming the engine is basically in good condition, properly maintained and your fuel management follows good practice, there’s a lot that can be done to improve the intrinsic reliability of systems. What’s appropriate for your own circumstances will depend on your boat, crew and sailing area.
1 High capacity fuel filters
The standard CAV296 filters fitted to most small yachts have a relatively small capacity. Upgrading to a filter with a larger capacity, such one from Racor’s range, can therefore reduce the incidence of fuel problems. In addition, they are easier and less messy to change. This is a policy routinely taken by charter companies, who may operate in far-flung destinations, yet need their boats to be as reliable as possible.
2 Twin parallel filter systems
Changing fuel filters and bleeding the system inevitably takes time, especially if it’s not the type of messy work you do in your day job. However, time can be in short supply if the engine stops at a critical moment, particularly if you’re short-handed.
For this reason many single engine motor boats have two filters fitted in parallel that can be switched in and out of the system. If the engine revs drop, or the motor stops completely, the clean spare filter can be switched into use in a few moments.
3 Vacuum gauges
When filters become clogged to the extent that the rate of fuel delivered reduces, the lift pump creates a partial vacuum in the pipework between it and the pre-filter. A vacuum gauge fitted here will give early warning of an impending problem – an increase of vacuum indicates a problem with the filter.
This is also why simply bleeding the air out of a fuel system that has a (mostly) clogged filter may get you going again. The increased vacuum pulls air into the system from joints in the pipework, or around the seals of the filter. In this situation bleeding the system won’t make the engine run for ever, but it may get you a few hundred metres past a critical point, especially if the motor is run at slightly lower revs than usual.
4 Check your fuel tank
Dirty water tends to settle in the bottom of fuel tanks, where it is only disturbed on a rough day at sea – often this is a precursor to clogged filters.
A further problem is the well documented one of microbes (diesel bug) that live in water in the tank, feed on the fuel and have potential to breed rapidly.
Any water will form a layer at the bottom of the tank, along with any dirt and microbes. Many tanks have a drain pipe at their lowest point, or an access point above this for a small pump. Both options enable a sample of liquid to be taken from the tank – if this turns out to be neat diesel then you know the fuel is in good shape.
If there’s crud or water present it’s worth draining off more fluid – in many cases you may need to run a further two or three litres through before you see clean fuel. If that’s the case you’re likely then to have cleared most of the problem. However, if you still don’t get clean diesel at this stage perhaps emptying and cleaning the tank would be a sensible precaution.