Maintenance Tip of the Week: Vessel Use 12/21/2015

Maintenance Tip of the Week – Vessel Use 12/21/2015

So, you have religiously followed the maintenance schedule for your engines as outlined in your manual. Everything should be good, right? Not necessarily. You need to pay attention to how you use your boat. If you only use your vessel 25 hours per year, fuel deteriorates, condensation occurs, and corrosion keeps up its’ never ending march. This is why your maintenance schedule is often broken down into time periods of use, as well as calendar time.

Diesel engines perform best when they are started and used frequently. Always follow the storage procedures as detailed in your manual if the vessel will be sitting idle for long periods of time.

Bad practice: Engine idling




A common misconception in the marine industry is that you must allow diesel engines to idle before putting them under load. With modern diesel engines, this belief is 100%, completely incorrect.

In fact, allowing an engine to sit at idle for long periods of time has the opposite effect: It increases wear on the engine, increases emissions, and wastes fuel.

How did this belief get started? Quite simply, people observed truckers at truck stops allowing their engines to idle and thought it was “Best Practice.” On older diesel engines, this may have been the case with fuel efficiency, and it is certainly the case with gasoline engines. Yet, a glance at a fuel consumption curve will show that a diesel consumes more fuel at idle, over a greater time period, than at startup. Additionally, in colder climates, it is believed that idling maintains the temperature. However, all modern diesel engines that are used in cold climates have sufficient heating to allow an easy start.

Unlike gasoline engines, modern diesel engines are designed to heat up under load. The fuel is under compression by heat, combusting more efficiently, and idling does not generate that necessary heat. Sitting at idle does not provide this load, and merely increases the friction in the cylinders. The load is generated on a boat under throttle. Idling for a period of time any more than an initial 30 seconds or so after the engine is started does nothing. No extra lubrication. No benefits. All marine engines manufactured by MarineDiesel are sufficiently lubed in this time period.

Finally, add in the fact that many jurisdictions in the world restrict unnecessary idling, due to emissions, this practice is one that should be eliminated. It just creates waste.