Yanmar diesel engine with Primary Filter on the left and Raw Water Intake and Impeller Housing on the Right
Yanmar diesel engine with Primary Filter on the left and Raw Water Intake and Impeller Housing on the Right

Tips for Bareboaters, Snowbirds & Casual Cruisers Part 2: Engine Troubleshooting

There are four common problems that will stop your engine. The most common is contaminated fuel or the fuel supply being compromised by a leak in the line. Simply running out of fuel, perhaps caused by a faulty gauge, is also a possibility.

Fuel lines, including the return line, should be checked for drips. Then check the primary filter, which should have a site glass making inspection easy. If sludge or dirty fuel is seen then the contaminant can be drained from the bowl by a tap on the bottom of the site glass. It is recommended to have access to some fuel (a gallon jug stored with other necessary engine fluids) for filling up the receptacle after it has been drained. This will help eliminate tedious priming of the system. Contaminated fuel may mean that the fuel tank needs cleaning, so keep an eye on it.

If a marine diesel engine overheats it will eventually stop, often with dire consequences. There are two cooling systems on most marine engines: a coolant (in a small tank) and a raw water (sea) heat exchanger. The coolant (a green liquid), which has a corrosion inhibitor, circulates around the motor, usually by a belt driven pump that also drives the alternator. Since the alternator provides the RPM gauge with its information, if it suddenly stops reading and the engine is overheating then the belt is likely loose or broken. The raw water circulates around the coolant by use of a rubber impeller. It enters the boat through a hull fitting with a valve and exits through the exhaust. If your boat overheats underway immediately look over the side where the raw water exits and check to see if it’s still flowing. This will affirm or eliminate one side of the problem. If the salt water is still flowing then there will be a problem with the coolant.

Whatever the cause of the problem it’s important to shut off the engine as soon as possible. Make sure you are not close to a lee shore, get a sail up and then shut down the engine. Do not open the coolant reservoir if it’s still hot and under pressure. When it’s finally cool enough to open, top it up and keep an eye on it.

If the raw water has stopped flowing it could be a number of different problems. First check the intake (turn off the valve before disconnecting the hose); sometimes a plastic bag gets sucked in and causes a blockage. Second, check the strainer for seaweed, and third, check the impeller for wear.  It is also prudent to check the engine oil; if the engine has seriously overheated the head gasket may have perforated allowing water to become mixed with the oil turning it the color of caffè latte— a serious problem.

A diesel engine needs air to operate (air, fuel and compression). If the air filter is blocked the engine will stop. For temporary relief of this problem remove the air filter assembly and the engine will start.

The engine will come to an abrupt stop if you get a line around the propeller. This is not an uncommon problem when motor sailing; a sheet or other line can easily fall over the side if not properly secured. There is also the possibility of a line from a fish trap or discarded net finding its way to your propeller. Usually the only way to solve this problem is to don mask and snorkel and cut it free. Some sailors may prefer to sail to an anchorage, while others may opt to cure the problem immediately. This will probably depend on wind and sea conditions at the time. The problem can have dire consequences and it behooves every sailor to tie stopper knots on all lines and to throw them down the companionway out of harm’s way (if not immediately in use). If this is not possible then secure them to the rail.

 

Useful Info:
Your engine’s raw water intake can be used as an emergency bilge pump by closing the valve, disconnecting the intake pipe and placing it in the bilge.

If you discover a serious ingress of water, check the thru-hull gland where the prop shaft exits the boat.

If your key switch or start button won’t start the engine jump start it by crossing the main battery lead on the
solenoid to the small positive wire originating at the
helm station.

Remember Murphy’s Law: If it might happen then it will happen. So be prepared.

Happy Sailing!

Editor’s note: Take care when working with motor oil and diesel fuel. Do not allow oil or fuel to enter the bilge. If it does, under no circumstances should you pump it overboard. This could result in prosecution and a hefty fine.

 

Julian Putley is the author of ‘The Drinking Man’s Guide to the BVI’, ‘Sunfun Calypso’, and ‘Sunfun Gospel’

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