Tips For Marine Diesel Engine Maintenance Tips For Marine Diesel Engine Maintenance

Marine Diesel Engines

Marine diesel engines are deceptively simple pieces of machinery. They’re much simpler than the petrol engine in your car but you still need to take the time for regular maintenance to avoid the nightmare of being stuck in a watery no-man’s-land.

The simplest thing you can do, apart from visual inspections, is to change the oil regularly. But there is more, so take note and if it seems a bit too much, schedule in an expert service from the guys at THT.


Raw water assists with cooling your engine but it can be blocked from doing just that. You must regularly check your sea water strainer to make sure it’s not blocked by seaweed, sea grass and plastic debris that can cause engine overheating.

Also critical to effective cooling is to regularly replace the sacrificial zinc anodes within the engine. Salt water is a corrosive. The zinc anodes are there to stop the salt water before it destroys other internal engine components. If the zinc anodes are not there or have been eaten away, your engine components will go and you’ll be calling in a diesel engine rebuilder.

Lubricating and Oiling Your Marine Diesel Engine

Oil Changes

Marine diesel engines run super-hot, under extreme pressure, so a good oil supply, changed regularly, is very important. 250 hours is our recommendation with either mineral or semi-synthetic oils. Using fully synthetic oils, you can extend service intervals to 600 hours with some engines, but sometimes the cost can outweigh the interval so 250 hour servicing is better.

Engine warm-up

Avoid running engines without load, for example: sitting in the pen warming up the engine. This can cause premature bore glazing. It’s much better to start the engine, throw the ropes and your engine will warm up as you idle out of the marina. Once your engine hits over 50 degrees, then increase your rpm to cruise speed.

Clean Fuel

Water in fuel is one of the biggest issues with diesel marine engines. Remember: fuel which is purchased from pumps near rivers and oceans is more likely to have a higher content of water and algae.

Just about every boat has a primary and secondary filter. The primary (or pre-fuel) filter is your first line of defence against water and larger impurities. The second is the engine filter. Install a primary fuel filter with a clear visible bowl at the base (like the Racor MA1000) and regularly check it before each trip. If you can see the fuel is “dirty” or there is algae, or you can see clear water at the bottom of the bowl (water is heavier than diesel), drain the water before it enters the engine and causes yet another reason to see a diesel engine rebuilder.

You should also diarise the replacement of your filters every 12 months but some boaties do it more regularly.

Marine Diesel Engine Rebuilders

It’s a pretty simple piece of machinery but sadly, it can’t run itself just yet!

Many boat owners choose to service their marine diesel engine themselves but if you want real peace of mind, it’s best you book it in with THT, Perth’s undisputed boat experts.

If you’ve already had an engine mishap, you could need our diesel engine rebuilder today. Whatever your need, contact THT and we’ll get you on the water in quick time and ship shape.