BETA
Based on Kubota tractor diesels but marinised in England according to Lloyds of London's standards, the entire Beta range of auxiliary diesels is freshwater (heat exchanger)-cooled and appears very well engineered. Cast-iron crossflow cylinder-heads are used with simple pushrod valve actuation from gear-driven camshafts.

Typically, freshwater cooling allows an engine to run at optimum (read: higher) temperatures for more complete combustion of the air/fuel mix. With Beta models the thermostat is fully open at 85°C instead of about 70°C for raw (salt) water-cooled motors.

Standard automotive-type 13psi pressure caps are used for the heat exchanger header tank and the anti freeze, anti-boil coolant used has a boiling point of 124°C. The water temperature alarm is set at 115°C, so there's plenty of warning before any overheating damage can occur.

Like the Nannidiesel and Volvo competition, even the smallest model in the Beta range has two cylinders and a comprehensive list of features. For example, there's indirect injection combined with Kubota's proven three vortex combustion chamber design for low exhaust emissions and glow plug pre-heating for positive cold starting. A 12 volt 40 amp alternator is fitted but a 55amp model (standard with the BD1005 and above) may be ordered instead.

One of the biggest sellers in the Beta range is the three-cylinder BD722, which develops 48% more power but weighs only 19% more than its twin-cylinder BZ482 counterpart. Three cylinders are considerably smoother than two without going to the complication of four.

The BD722 measures a compact 660mm from alternator pulley to gearbox coupling (only 65 longer than the BZ482), is 480mm wide and 596 tall. The alternator is mounted at near the top of the engine and the starter motor, though a little lower, is still well above the engine mounting feet and away from bilge water. And being designed specifically for yachts, the BD722 can be installed at up to a 15° angle (though I don't recommend this or too much prop thrust will be lost) with a heeling tolerance of 25°.

Being designed for commercial use, all Beta diesels have quite lengthy service intervals, every 200 operating hours or once a year after the first 25 and 50 hours. However, knowing how few hours are clocked up on most yacht auxiliaries, I recommend changing the engine oil (using an SAE 15W40 diesel truck-type oil) and filter every 50 hours or six months Replacing the fuel filter and coolant is required every 600 hours or two years.

Servicing all models appears straightforward with components such as the oil and fuel filters easily serviced, while both the salt and freshwater-cooling pumps are at the forward end of the motor for instant access.

When compiling this guide no gear ratios for the shaftdrive models were provided, but saildrive models has a usefully low 2.25:1 reduction.

For more information on Beta diesels, contact Gary Townsend, tel (02) 9525 0011.

SOLE
Sole marine diesels (pronounced: sol-lay) first appeared in the early 1970s under the Stuart Turner label when the latter company wanted a lightweight marine diesel to supplement its classic range of two-stroke petrol inboards.

As the Sole brand name became better known, the models were sold under their own label. All models under 70hp are based on Mitsubishi tractor engines and marinised by the Sole factory in Spain.

My introduction to Sole was back in '84 when I tested an Arends 33 cruising yacht powered by a four-cylinder Mini 34.

At a time when most diesels in this power range were relatively noisy direct-injection saltwater-cooled units, I was particularly impressed by the engine's easy starting, smooth running and overall quietness.

As with the all the competition apart from Bukh and Yanmar, the smallest Sole model has two cylinders and all are freshwater-cooled.

Like their Beta competition, all have cast-iron crossflow cylinder-heads, indirect-injection and glow plugs for easy cold starting. Alternators are mounted up by the rocker cover with starter motors well above the motors' mounting feet.

Models up to the Mini 48 can operate continuously at a 20° trim angle and up to 25° of heel.

Again, being designed for commercial use, they have flat torque curves well suited to installation in heavy displacement cruising yachts. For example, the Mini 11 develops its maximum torque at 2700 revs, but still produces 86% of it at just 1500 very good for a twin cylinder diesel.

Mechanical gearboxes are used with the models listed hereabouts and a wide range of ratios are available.

For example, even the Mini 11 has a standard 2.25:1 ratio but a 3.05:1 reduction may be fitted. This choice is also available with the Mini 17 and 26.

The Mini 34 has a 2.25:1 ratio but you can opt for 2.5:1 or 3:1 ratios, while the Mini 48 has 2:1, 2.5:1 and 3:1 options. The Mini 62 has the choice of 2:1 and 2.5:1.

Available fitted to Sole's three smaller models (Mini 11, 17 and 26), the saildrive has a 2:1 ratio.

For more information on the above Sole diesels (and its full range of marine engines to 270hp), contact Don MacGeache at Headland Engineering, tel (02) 9939 1966.