When we acquired our 43-year-old cruiser Maximus, we asked PBO’s engine expert Stu Davies and wife Laura to show us how to service the  Volvo MD2020 engine.

They drove all the way from North Wales to Chichester to demonstrate everything from checking for diesel bug to replacing fuel filters and tightening the alternator belt.

The full 8pp article appears in the April 22 edition of Practical Boat Owner, which is on-sale now and available from Magazines Direct.

Alternatively, you can read the full article on servicing a marine diesel engine here.

PART 1 – the fuel system, diesel bug and emergency stop

In the first of the 3-part series we meet Stu and Laura Davies onboard Maximus, and they take a look at the 18-year-old marine diesel engine. Even though the Maxi 84 has been laid up in a boatyard for two years, Stu concludes it’s in pretty good nick. He considers what spares should you carry onboard, looks at the fuel system and explains how the fuel gauge works and how fuel is polished. Stu inspects the tank for diesel bug and finds evidence of old bug. He demonstrates how to stop the engine in an emergency and how to engage the gears from the engine itself. He checks the antifreeze, discusses what to do with rust, and how to tighten valves.

PART 2 – replacing the impeller and primary fuel filter

Next, Stu and Laura Davies point out the anti-syphon, explain how a Speedseal works and why it’s such a great piece of kit. We remove and replace the impeller (note how the blades are worn), and learn how it works, along with the engine cooling system. Stu then replaces the primary fuel filter and checks for water in the system.

PART 3 – replacing the secondary fuel filter, changing oil and tightening alternator belt

In the final part of the series, Stu and Laura Davies replace the secondary fuel filter and use the oil filter pump to suck fuel through the system to check for leaks. Stu explains how to use a filter strap wrench. He then replaces the oil filter and the engine oil and checks the sail drive leg oil. He demonstrates how to change and tighten the alternator belt whilst Laura gets to work tackling rust. We take a look at the water strainer, attach the engine starter battery and finally it’s time to start the engine.

After two years laid up in a boatyard, will Stu and Laura’s engine service be enough to get the MD2020 up and running again?

Maximus boat survey

Before we acquired Maximus we asked marine surveyor Ben Sutcliffe-Davies to do a survey. In the first part of the boat survey he used a moisture meter to check how dry the hull was, explained when it was time to scrape back antifouling and flagged the dangerous boat gas locker.

“For the sake of £40, I think the gas detector wand is a great piece of kit,” explained Ben. “I mainly use this on narrowboat surveys because they’re notorious for leaky gas lockers but it’s well worth having.”

• Buy the TPI 725L combustible gas detector from Screwfix here

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He also explained the importance of laying up your boat level when storing it ashore.

In the second part of the boat survey Ben went down below and flagged issues such as a dangerous gas oven and corroded seacocks. He took a look at the engine, and explained how the Volvo MD2020 works, but wasn’t able to start it because the batteries were flat.

You can follow our progress as we refit the PBO Project Boat here and on the PBO Project Boat Maximus YouTube channel.

Thanks to our Project Boat Supporters

Dell Quay Marine, Osculati, Raymarine, Shakespeare Marine, TruDesign, Screwfix, Coleman Marine Insurance, MDL Marinas, Premier Marinas, seajet,, Clean to Gleam, West System, Farécla, Navigators Marine, RYA, Aqua Marine, Ecobat, Victron Energy, Scanstrut, T Sails and XP Rigging.

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