Talking Torque: Lightweight Baby

Westerbeke's smallest genset is packed with features

We're all used to on-board diesel gensets in cruisers over 10 metres, enabling us to have air con and all-electric galleys. Fine if the main engines are diesel, but what about cruisers that have inboard/stern drive petrol engines or are powered by multiple high-horsepower outboards? Why have a diesel genset when the main fuel is petrol?

Westerbeke's recently-released 3.5 MCGA is the company's least powerful petrol genset and weighs only 102kg, compared to the smallest Westerbeke diesel genset, which develops 5kW but weighs 202kg. This genset has a mechanically-controlled three cylinder diesel, whereas the 3.5 MCGA has all the features we're used to in modern petrol inboards, stern drives and four stroke outboards.

THE NITTY GRITTY

Forget the old petrol gensets that had carbies and manual or automatic chokes. The 3.5 has multipoint EFI and electronic governor with full plug in diagnostics capability, while a catalytic converter in the exhaust system helps this genset meet current US EPA and CARB exhaust emission standards. The 3.5 also has US Coast Guard 33 CFR — 183 compliance for onboard petrol gensets. In conjunction with the electronic governor, the EFI has instant throttle opening response and reduces engine ‘bog down’ as it comes under load from compressor-based appliances such as air con units or fridges that have high starting loads relative to normal current consumption. In the old carbie gensets there was always lag until the mechanical governor kicked in and increased fuel flow to the engine by opening the carbie throttle flap.

The engine is a twin cylinder horizontal OHV unit that has an alloy cylinder head and block and heat exchanger cooling with a gear driven sea (raw) water pump and belt-driven fresh water circulating pump. The coolant capacity of 1.38 litres is more than adequate for the 330cc engine. However Westerbeke states the engine has only two main bearings whereas I'd prefer three for better crankshaft support.

Unusually, the engine has fixed revs of 2500 instead of 3000rpm from a genset that supplies 230V and 50 Hertz for Aussie appliances. This ensures a longer service life and lower noise levels, eliminating the need for bulky sound proofing. 

The 15A brushless alternator is air cooled and has excellent frequency stabilisation of only one per cent, while the voltage stabilisation is still very good at plus or minus five per cent. A 12V 600W starter motor is fitted and needs a minimum 70CCA (Cold Cranking Amps) battery, so a 40amp/hour automotive battery with 330CCA would be perfect. Such a battery weighs only 9.5kg and at around $110 is better value than a dedicated marine starter battery, provided it's mounted on a shock-absorbing base. A 5A 12V alternator is fitted for charging the starter battery. The belt drive for starter battery alternator and fresh water pump is enclosed by a shroud. You can tell the 3.5 is made in the litigious US!

Standard are audible warnings and automatic genset shut down for engine over speed or under speed, low oil pressure and high coolant temperature.

The 3.5 is longer than it is wide or high, so could be mounted longitudinally in a bilge, obviously ensuring there's adequate under-deck ventilation for engine air intake and venting hot cooling air from the alternator. Remember also that catalytic converters normally run at 800 degrees to function correctly so adequate lagging will be needed in the exhaust system and overboard discharge, even though the sea water mixed with exhaust will substantially reduce this heat. Obviously if the boat is powered by multiple outboards then a dedicated sea cock with strainer will need to be installed for the genset.

An optional top-mounted drip cover is available but without this the 3.5 is 687mm long and 381mm wide and high.

THE WRAP

Apart from the common fuel advantage in a petrol-powered boat the beauty of a petrol genset is that with only basic automotive-type fuel induction such as multipoint EFI it can easily meet relevant exhaust emission compliance. Petrol engines are easy to maintain and service and are quiet compared to diesel engines — with none of the exhaust soot to stain the topsides of your investment. 

As of March 2020 the 3.5 MCGA retailed for $13,420 including GST.

For more information on this unit visit Marine Energy Systems at sales@marineenergy.com.au or call +61 (07) 5502 7771 

QUICK SPECS

Westerbeke 3.5 MCGA

Type: Twin cylinder OHV EFI petrol

Max output: 6 brake horsepower at 2500rpm

Displacement: 330cc

Bore x stroke: 61 x 57 mm

Type: Brush less

Volts: 230 +/- 5%

Hertz: 50 +/- 1%

Engine and alternator: 102kg dry

*Brake horsepower/metric horsepower or PS