Boat Diesel – Good engine practice

To start a diesel engine after a long lay-up or a change of lubricating oil filter you will need to follow a few simple steps.

First put the gearbox into neutral. Open the raw water and fuel valves, lift the exhaust valve decompression levers if fitted and hand crank the engine about 20 revs. Alternatively, activate the stop solenoid/stop cable, then turn the engine over 20 or so times on the starter motor. Either way, you are circulating lubricating oil around the engine.

Now start the engine, setting the speed control at 1200-1500rpm, unless the manufacturer’s instructions are different. Some engines need full speed, ie maximum fuel.

Initially, use the engine’s cold start aids, such as glow plugs, inlet heaters or extra fuel.

After the engine starts, run it at 1200-1500rpm without load for a few minutes to warm up and check that:
1. Water is coming from the exhaust outlet.
2. The green oil pressure light is off.
3. The amber light on the charging circuit is off.

Starting normally
In warm weather most engines will not need any cold start procedure and will fire immediately. But slow running engines may need their cold starting aid, especially if it is the type that delivers extra fuel.

The fuel cut-off valve should be pointed out to all crew members. Handle in-line is on. It should be sited close to the tank but outside the engine compartment in case of fire.

With the gearbox in neutral, engine water and fuel valves on, start the engine using the starter motor, by pushing the button or turning the key. If the engine is reluctant to start, go back to the cold starting procedure. Reluctance to start can be due to sticky injectors. They will need servicing.

The water inlet strainer is the first line of defence against large debris entering the cooling system. It can easily become clogged with weed or marine growth and crustaceans, restricting water flow, causing overheating.

This two-cylinder engine is fitted with exhaust valve lifters (decompression levers) which make hand-starting feasible. Raise the levers, or in this case push them over to the open position. Crank a few times to prime fuel and get the flywheel moving.

When the engine is turning over as fast as you can crank it, drop the levers. This will close the exhaust valves and give the engine the compression it needs to fire.

Older engines fitted with combined starter/generators, or a hand crank, will need to have their exhaust valve decompression levers lifted before the engine will turn. Once the flywheel is turning at speed, the levers are dropped, the exhaust valves close and the engine should start.

If the engine doesn’t start within 20 seconds or so, switch off the key, wait for all moving parts to stop and try again after a pause to let the starter motor cool. If it still won’t start, turn off the raw cooling water at the inlet valve to prevent the exhaust filling with water which could then flow back through the exhaust valves into the engine.

This solenoid-operated stop switch will give little trouble, but malfunction is unlikely to be easy to fix. A good troubleshooter will be able to pinpoint the problem and rig a manual stop cable.

When it does start, remember to turn the water back on and check that:
1. Water is coming from the exhaust.
2. The green oil pressure light is off or the gauge is registering.
3. The amber light in the charging circuit is off or the voltmeter is registering 13+ volts.

Turbocharged engines should be run for a few minutes at low speed to warm up before any load is applied, or according to the manufacturer’s instructions.

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