Following some basic operating procedures for the diesels in your new boat can make a big difference to the reliability, running costs and resale value of your investment. 

Modern diesel engines are incredibly reliable pieces of machinery provided that some care is taken with running them in and maintaining them according to the manufacturers’ requirements.


The best preventative maintenance is to
regularly service your diesels as per the manufacturer’s recommended intervals, based on a record of engine hours from your hourmeters.

If in doubt about these intervals, a rule of thumb is an oil and filter change after the first 20 hours then every six months or 100 hours. Turbocharged diesels “stress” engine oil and dirty it far faster than petrol car engines, so an oil and filter change every six months will dramatically increase your engine’s lifespan.

Onboard gensets – which normally reach 1500 – 3000 revs from cold, and are expected to supply current without a warm-up period – should be serviced every 100 hours or six months.  


Get a good quality toolkit so you can perform regular engine maintenance and make emergency repairs on the run. Avoid those cheap imports… your toolkit is one thing you just can’t skimp on.

Your spares inventory should include engine and gearbox oil. This should always be the same brand and SAE rating as in the sumps. You should also carry engine coolant with corrosion inhibitor, drive belts for your alternator and spare air filter elements.

You may not expect the filter elements to fail but I can assure you from my time as a charter skipper that this can happen without warning, resulting in a sudden loss of power which could be disastrous when crossing a bar.

If you are planning a coastal voyage always carry spare salt and fresh water cooling pump impellers, cooling water hoses, spare Jubilee clips and fuel and oil filters.  

Don’t forget your genset. Your spares inventory for your main engines needs to be replicated for your genset if you have one.

You might also like to take a set of spare alternator brushes.

Checking the fuel sedimenter.

Checking the fuel sedimenter.



Even though it may seem tedious, at the beginning of each day I recommend checking the oil level on the engine and gearbox sump dipsticks to ensure the level is at the “max” line.

You should also check the coolant level in the heat exchanger expansion tank and ensure corrosion inhibitor has been added by checking the colour of the coolant in the filler cap neck.

As diesel fuel is hydroscopic (attracts moisture from the atmosphere) the fuel sedimenters should be checked for excess water content and drained according to the manufacturers’ recommendations. Most diesels have self-bleeding fuel systems but if not, the manufacturer can advise on the correct procedure.

To reduce moisture in the fuel, it’s worth topping off the tanks at the end of a day’s usage. Keeping your tanks full means there’s less moisture to be absorbed by the diesel.

Take a good look around the engines for any oil leaks or oil in the bilges which, if the engines are in good operating condition, should be bone dry. And just ahead of the shaft logs are small wells which should also be free from water, especially as Riviera fits dripless shaft log seals.

Although alternator drive belts normally don’t require replacing for at least 1000 hours, check these for fraying and correct tension on the pulleys by depressing them with a thumb. The engine manufacturer can advise how much pressure to apply, according to belt size.


Checking engine bolts and mounts.



As all diesels are fuel injected, leave the throttles closed when starting or excess fuel will be supplied to the combustion chambers, resulting in black smoke. When the “ignition” keys are turned the engine warning system sirens should sound, and stop immediately when the engines start.

If your engines have mechanically controlled injection with fixed fuel-spray timing and haven’t been used for several days, there may be some light grey smoke from condensation in the fuel. This should clear in a couple of minutes.

Mechanically-controlled engines will normally blow some black smoke on starting, due to initial fuel over-supply but again this should clear quickly. Also when manoeuvring with quick throttle bursts the smoke will appear.  

But if black smoke appears from electronically-managed engines then something is amiss in the management system and should be diagnosed without delay.

After checking the exhausts, make sure all instrumentation is functioning correctly. Especially keep a watch on the voltmeters, oil pressure gauges and temperature gauges.

At low speeds diesels run cooler than petrol car engines and take several minutes to reach normal operating temperature, so allow at least five minutes at idle before engaging gear and then don’t open the throttles past 1000 revs for the first 10 minutes. This will allow engine oil to reach the turbocharger bearings and build up a sufficient film of oil before the turbos come on boost.

Checking main engine fluid levels.


Checking gear box fluid levels.



Your new diesels have been correctly propped at the factory to ensure they reach their Wide Open Throttle rev range with an average load aboard. But if you are taking a tribe out for the maiden voyage, the engines may be over-propped, and care must be taken not to overload them.

I recommend that during the running-in period you limit passengers aboard to no more than three or four adults.

Once the engines have been fully warmed up there should be no black smoke at sub-planing speeds or on the plane. If your Riviera has mechanically-controlled diesels there may be some black smoke on transition from sub-planing to fully-planing speeds (about 18 to 24 knots depending on hull length) but otherwise only spent cooling water should appear from the exhaust outlets. With electronically-managed diesels (such as the QSM 11 Cummins) and Volvo’s Kompressor-series motors, no smoke should appear during this transitional period.

According to Richard Minard of Minards Marine, which for years has sold both recreational and commercial diesels throughout the Pacific Islands, an engine’s running-in period will vary according to how frequently the motor is used and the anticipated operating load.

For example, with frequently used motors about 20 hours will suffice. After the initial 10 minutes, the motors can be gradually opened out to within about 200 revs of wide open throttle (WOT) for short periods of time, returning to 600 revs less (depending on the engines’ WOT revs) for a cooling period. This will ensure the bearings and piston rings bed in correctly.

According to Hylton Hamilton of Hamiltons Marine, which sells Volvo and Mercruiser diesels, the engines must be kept at least 200 revs below WOT for the first eight hours. Hylton believes that Volvo’s recommendations are a good guide to follow. After an initial eight-hour period, recreational-rated motors must not be operated at WOT for more than one hour in any 12.

For light duty commercial rated motors (such as those in charter boats), Hylton suggests the same initial period, followed by no more than two hours of WOT in any 12.

Apart from the brief WOT periods, the engines must be run continuously at no more than 90 percent of maximum output or about 200 revs below maximum.

After a long run, cool down the engines at about 1500 revs in gear for about 10 minutes before idling the engines. This will ensure the turbo stops spinning before shutting down the engines.

Don’t forget the genset. When it’s new, I recommend allowing it to warm-up for several minutes before switching on appliances, limiting current draw to about half to three quarters of the rated maximum and varying the load by switching electrical appliances on an off for at least a few hours. This will help bed in the bearings and piston rings.

If your genset produces its rated current at 3000 revs, I also recommend maintaining at least half the rated current draw at all times. My genset testing has shown this to reduce engine damage from light loads and increase engine lifespan.


Sometimes forgotten, the genset, hidden behind the sound shield should be checked for oil level. 



Most engine reliability problems with turbocharged diesels result from extended periods of low revs, below the point where the turbos start to come on boost. This is more common with mechanically-controlled diesels than electronically-managed units because the fuel spray timing is fixed, and below the optimum rev range the timing is too advanced for effective combustion of the air/fuel mix.

Both Richard and Hylton told me that no diesel likes idling for extended periods, even when run-in fully, and if used this way most diesels can suffer glazed bores that will need re-honing down the track. The first indication of this is reduced power and some bluish oil smoke on cold start-up.

Even when using your Riviera just for day trips, whenever possible operate the boat at planing speeds for at least 15 minutes during the day to reduce bore glazing. A good engine “work-out” also raises engine temperature to reduce condensation in the cylinder bores, which eventually finds its way to the sump and increases oil “sludging”, affecting the oil’s ability to adequately lubricate the bearings and rings.

The more diesels are used, the longer they last. Using your boat as much as possible will also help reduce hull growth and the frequency of antifouling, which we all know is such a waste of time.

Remember Rivieras are made to be enjoyed, not to sit at a marina gathering slime. The water beckons!


  • Good quality toolkit?
  • Spare parts?
  • Check engine and gearbox oil levels before your start?
  • Check engine and gearbox oil levels after you shut down at the end of the day?
  • Check for oil leaks around seals and shafts
  • Check water levels in your fuel
  • Fill up at the end of your trip
?R-Marine 2008 Privacy Statement | Legal Notices | Site Map