Boat Engine Review: Volvo Penta D1-13

Volvo Penta's smallest marine diesel has it right where it's needed

There's a lot of competition in the twin cylinder baby diesel market, with tractor/industrial base offerings from Beta Marine, Nanni Diesel, Sole, Volvo Penta, Westerbeke and Yanmar. All have heat exchanger cooling for engine longevity.

Of these, Nanni Diesel, Volvo Penta and Yanmar are the most popular with Westerbeke being a stand out due to its more affordable pricing. Nanni Diesel's offering, the N2.14, has the smallest piston displacement at 479 cc while the Westerbeke 12D has the largest at 630 cc. The D1-13 is 510 cc and Yanmar's 2YM-15 is 570 cc. The N2.14 is the lightest at 92kg for the engine and mechanical gearbox, the 12D weighs 102kg, the D1-13 is 111kg and the 2YM-15 is 113kg.

The peak torque outputs are very similar: 29 Newton metres at 2000rpm for the 2YM-15, 30 NM at 2600rpm for the N2.14 and 31 NM at 2200 to 2400rpm for the 12D. 

But while the D1-13 develops only 29 NM, it does this from a low 1600rpm right out to 2800rpm. Never before have I seen such a flat torque curve from a mechanically injected diesel.

Having maximum torque developed so low in the rpm range is a real plus for a yacht auxiliary. There's plenty of ‘grunt’ on hand for manoeuvring in tight marinas or when motoring into a stiff headwind. Perfect for a cruising yacht such as the Compass 28, which over the years of reviewing small diesels has been my benchmark yacht for re-powering from the old horizontal cylinder Yanmar YSM8, which developed 7.9 BHP at 3200rpm, about 20 NM at 2500rpm and weighed 112 KG with gearbox. In headwinds over 20kts, the Compass 28 could barely make headway with this engine. But it was very reliable and had features such as raised hand starting, whereas the current twins rely solely on electric starting.

The full-keel Compass 28 displaced 3.25 tonnes so even another 9 NM of torque makes a huge difference, especially when it's produced over such a large rpm range in the case of the D1-13. Incidentally with its shorter overhangs and narrower beam than the Compass 29 and an impressive 55% ballast ratio the 8.6 metre 28 was faster and a much better sea boat than the 29. From 1970 to 1981, 400 28s were built and build quality was so good that boats built in the mid-1970s are still a sound investment and affordable at less than $20K.

In the details

Interestingly the D1-13 weighs the same as the old single cylinder Volvo Penta MD5A, which developed 7.5 HP at a low 2500rpm (torque unknown) from 443 cc. Due to its massive flywheel, this raw-water cooled engine was one of the smoothest-running single cylinder diesels ever made and had lever-operated decompression for easy hand starting. Unfortunately, although its forward-mounted flywheel did place engine weight closer to midships for better fore and aft hull trim, it meant locating the water pump impeller at the aft end, which was difficult to access in the narrow confines of a yacht bilge.

This is where tractor/industrial engines with their aft mounted flywheels score. The raw water and freshwater circulating pumps plus the alternator are easily reached, as is the oil filter.

As with its direct competition, the D1-13 has a cast iron cylinder block and head with gear driven camshaft that operates the overhead valves via push rods and rockers, a proven combination for reliability. The exhaust manifold is freshwater cooled for a long life, while the exhaust elbow is salt-water cooled.

The 14-volt, 115-amp alternator provides plenty of juice for on board accessories and is mounted high up on the cylinder block. Sensibly, Volvo Penta has fitted two stop switches, one in the instrument panel and one on the engine, should adjustments be needed with the engine running.

The standard instrument panel includes an analogue tachometer with digital hour meter plus the usual warning lights and alarms for low oil pressure, engine overheat and low voltage.

The D1-13 was designed to use the same diesel available in Oz, 840 grams per litre instead of being rated for the denser 860 grams available in Europe and some Asian countries. Volvo Penta doesn't stipulate its recommended oil viscosity, but I suggest a diesel-specific SAE 15W40 oil and changing the oil and filter every 200 running hours or annually, although if the engine is used infrequently, the oil and filter should be changed every six months.

Volvo Penta offers two types of mechanical gearboxes, both having reduction ratios of 2.14:1 or 2.63:1, the former better for yachts. The MS 15A box has an eight-degree down angle at the output flange, while the MS 15L has a straight output and better for repowering hulls such as the 28 as major work to modify the engine bearers shouldn't be needed.

Alternatively, for modern yachts the sail drive version has a 2.19:1 ratio and increases overall engine weight to 125 KG. With mechanical gearbox, the D1-13 is 662 mm long, 483 wide and 518 mm high. The YSM8 was 608 mm long, 602 wide (due to the horizontal cylinder) and 436 mm high, so the D1-13 should fit nicely into the bilge of a 28, with better access around the engine and much easier valve clearance adjustment.

The wrap

Having maximum torque available over such a broad rpm range makes a huge difference for easier low-speed handling, particularly with full keel hulls such as the 28 that are notoriously slow to respond compared with fin keel and spade rudder hulls. Volvo Penta has decades of experience in building small yacht diesels and with scheduled maintenance, the D1-13 should provide reliable power when needed.

For more on the D1-13 Google Volvo Penta, visit a local dealer.

Volvo Penta D1-13 Sea Trials

As the D1-13 has mechanical engine control, I suggest not running it continuously below 2000rpm or above 2800tpm. I also suggest propping the engine so that under normal loading it will reach 3300rpm. This will allow for some prop and hull fouling between slipping.

Note that 90 percent of maximum torque is available at 1200rpm and 93 percent at WOT.

Volvo Penta D1-13 Quick Specs

*Brake horsepower/metric horsepower or PS

Related Articles:

Volvo Penta Reviews

4 Steps To Finance A Boat