Volvo penta marine diesel engines review

It’s a sad fact of life that fat loves me. Sure, I do stretch yoga and power walking but I’ve come to accept the flabulous look. So, do I want an engine that changes this look? I think not, especially as my nickname has been “big girl” ever since I confessed to friends my love of watching dolphins.

Therefore, in a small cruising yacht what would keep my look without being too complex? A three-cylinder engine naturally, only slightly heavier than a twin but less complex than a four.

The Volvo Penta D1-20 is such an engine and weighs only 16 per cent more than its twin-cylinder Volvo Penta D1-13 counterpart but develops 53 per cent more power and 62 per cent more torque.

VOLVO PENTA D1-20

Released on the Oz market in 2005, the Volvo Penta D1-20 diesel engine displaces 760cc and develops 18 brake horsepower (one horsepower equals 746 Watts) at the crankshaft and between 2800 and 3200rpm with a maximum torque output of 47Nm at 2400rpm, which is also the recommended cruising rpm for this engine. Unfortunately, the torque curve is more peaky than the Volvo D1-13 but still 40Nm are on tap from 1200rpm and 41Nm at 3200rpm, so it’s still pretty flat.

The Volvo Penta D1-20 diesel engine has a pushrod OHV engine with cast iron cylinder head and block. Heat exchanger cooling is standard with the exhaust manifold freshwater cooled for easy connection to a hot-water system. The inline fuel injection is driven from the camshaft with glow plugs fitted for easier cold starts, just as well as the indirect injection system needs a compression ratio of 23:1. So hand-starting is out, not a bad thing if you lack the strength to crank-up a diesel but don’t want to embarrass yourself in front of friends.

The saltwater cooling pump is gear driven and the centrifugal freshwater pump by vee-belt, the standard voltage-regulated alternator pumping out up to 115amp. Both the alternator and starter motor are mounted high on the block, so the engine will keep running even if you’ve been slack in pumping out your bilge.

Complete with eight-degree down-angle box, the Volvo Penta D1-20 engine weighs 131kg and measures 681mm long, 471mm wide and 534mm high. The reduction ratios are 2.35:1 or 2.72:1, the latter more suited to a displacement-hulled launch. A saildrive model is also available and weighs 144kg complete with 2.19:1 reduction ratio, but only a dog clutch. However, gear oil can be replaced without slipping the boat and the engine may be mounted ahead or aft of the leg to reduce installation impact on the accommodation space.

Servicing the Volvo Penta D1-20 diesel is straightforward and I recommend changing the oil and filter every 100 hours, or annually if using the engine infrequently. A good quality mineral-based diesel SAE 15W40 oil can be used in warmer climates or SAE 10W30 in Tassie and our southern oceans.

ENGINE TORQUE AND FUEL ECONOMY

On-water peformance should be like other small Volvo Penta diesels I’ve reviewed, unfortunately I haven’t tried this one in a boat. So again it’s all theory but at least the tech specs supplied to me by Volvo Penta helped analyse the best points of this engine.

Because the engine output is so small compared to the displacement of the hull it’s likely to be pushing it’s essential not to over-prop the engine. It should reach 3200rpm with normal passenger, fuel and water loading, even though it will be running fast and light at low rpm. And having fixed injection timing, the Volvo Penta D1-20 engine should not be run continuously at less than 2000rpm or cylinder bore glazing from fuel oversupply may occur, as all mechanically-injected diesels have over-advanced injection timing below the maximum torque band and retarded above. The worst treatment for a diesel is not working it hard enough.

Note how high the fuel flow is at low rpm compared to the power absorbed by the prop. When idling, the engine is running at only two per cent efficiency, whereas at Wide Open Throttle the engine efficiency is around 36 per cent or 21 after prop losses have been accounted for. Translated, this means the engine is using only 36 per cent of the fuel’s energy to develop power. A hybrid drive works better at low speeds but still has a maximum overall efficiency of only 15 per cent. So it’s a good thing the fuel flow for a small diesel is so low!

THE TRADE-A-BOAT VERDICT

Volvo Penta knows how to design and build small yacht diesels and the D1-20 is no exception. Even though its marine-specific direct injection engines have long gone due to failure to comply with exhaust emission laws, using a tractor-based engine works very well as the torque curves are relatively flat, essential for confident boat handling in the confines of a marina.

From trying three-cylinder diesels of other makes I know, the D1-20 should provide seamless power delivery without opting for four cylinders. Long live flab!

For more information on the D1-20 contact Volvo Penta Australia. 

VOLVO PENTA D1-20 ENGINE PERFORMANCE

* Engine data supplied by Volvo Penta.

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