MAN Marine Diesel Engine Maintenance Plan- updated June 2025

MAN Marine Diesel Engine Maintenance Plan- there is a lot of confusion out there on these motors and I wanted to set the record straight.

The MAN common rail engine started appearing in recreational marine applications in 2005 and is widely used today in horsepower applications from 600hp to 2000hp.  It comes in inline 6, V8, V10 and V12 configurations.  They were regarded as a huge leap in technology  due to its increases in fuel efficiency and performance and its decreases in vibration, smoke and noise.  Since its introduction it has received regular updates over the years and only gotten better.

MAN common rail engines are known for having a great power to weight ratio, minimal vibration, minimal noise and little to no smoke.  Think German engineering- they are finely tuned and technologically advanced engines.

A large point of confusion here is people believe the MAN engines require more intensive service intervals and are more costly to maintain than other engines. This is really no longer true especially with the latest iteration of the MAN V8 and V12.  The service intervals are actually less than CAT, specifically when it comes to the cooling systems.

in 2018 MAN changed from a tank and bundle engine cooling system to a more simple plate cooling system.  This changed the requirement for servicing the cooling system from every 2 years to every 4 years.  The newer plate cooling system is more durable and does not require repairs/replacement as much as the older tank and bundle system.

For most basic services like an oil change or simple part swap out any competent diesel mechanic can get that done, however if it is a warranty or more detailed engine issue you really need a certified MAN engine tech.  90% of the places where most people boat there is a MAN dealer not far away, but in some cases where you have a more complex issue you may find yourself flying someone in.  These instances though are pretty rare as MAN makes a great engine, and as long as you keep up with the recommended maintenance you will not have an issue.

The following is a basic guideline of the MAN Marine Diesel Engine maintenance plan. NOTE THE DIFFERENCE IN THE 2 and 4 YEAR INTERVALS between the TANK AND BUNDLE and PLATE HEAT EXCHANGERS.  See the link at the bottom to download the PDF of the plan directly from MAN for both types.

Every 200 Hours or Once a Year (same with all common rail MAN engines)

• Change fuel filter cartridges
• Clean fuel pre-filter
• Drain water for aux. fuel filter
• Check shaft alignment
• Check condition of raw water impellers
• Check all hose clamps, pipe connections and bolts
• Check belt for proper tension adjust/replace as necessary
• Check all hoses for leaks
• Check all engine alarms and instruments
• Check oil and coolant levels

Every 400 Hours or Once a Year (same with all common rail MAN engines)

• Change engine oil
• Change engine oil filters
• Change filter element of crankcase breather
• Change air filter

At 400 Hours, 800 hours and every 800 hours after that (same with all common rail MAN engines)

• Check and Adjust Valve clearance as needed

Every 2 Years (FOR 2005-2018 tank and bundle cooler type MAN engines only)

• Change both valve caps on expansion tank
• Remove and clean, flush intercooler and charge-air pipes
• Clean turbochargers
• Remove and clean, heat exchanger pipe cluster

Every 4 Years (FOR 2018-current plate cooler type MAN engines only)

• Remove and clean heat exchanger plates
• Remove and clean charge air cooler

Every 4 Years (same with all common rail MAN engines)

• Change engine coolant
• Change all hoses

Click Below to Download the Maintenance Plan Directly from MAN

2005-2018 tank and bundle MAN Common Rail Engine Maintenance Plan

2018-current plate MAN Common Rail Engine Maintenance Plan

Credit to www.MarineDieselSpecialists.com for assistance with the above information!