Diesel engine fluids

The key to a smooth-running diesel engine is making sure you look the fluids, as John Panye explains

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The subject of diesel engines, maintenance and breakdowns is seemingly never-ending. Many of the issues with yacht diesel engines are entirely preventable. They require simple and basic maintenance and inspection by boat owners, without the need for costly marine mechanics.

I started my marine career as a junior engineer on old British tramp cargo ships, a reset from my then-not-long-completed electrical fitter/mechanic apprenticeship.

Several years of sea time on the engine room plates with some very skilled and competent engineers eventually rubbed off. One mentor had his own mantra: "It's all about the fluids, laddie, look after the fluids, and your engine will look after you", which he used to frequently intone along with several other expletives, while also encouraging me to better watchkeeping diligence.

As everyone knows, the primary engine fluids are the seawater cooling system; the engine freshwater cooling system; the engine lubrication oil systems; the diesel fuel system and the transmission oil.

RNLI statistics reveal that the main emergency callout reasons are attributable to machinery failure. The primary causes include overheated engines, diesel fuel contamination, filter blockages, rubber belt failures and pump impeller failures.

The seawater system

The seawater cooling system is reasonably simple, but I'm surprised at how many people rarely monitor it until an overheating event occurs. Unlike commercial vessels there are no pressure or temperature gauges, and rarely any alarms on seawater systems, although it would be good if there were.

When you get a sudden rise in engine temperature and lowered oil pressure, the usual go-to source is the seawater pump impeller after a quick look over the stern to check the exhaust outlet.