Review: Nanni Diesel QFM3.5M genset

By: Andrew Norton

This Nanni Diesel QFM3.5M genset gets boaters away from dangerous cooking fuels

Review: Nanni Diesel QFM3.5M genset
A Nanni Diesel genset should give you years of trouble-free operation. It also makes your boat way safer than using LPG or even butane for cooking.

Eliminating alcohol or LPG simply translates to safer boating. In my opinion, an all-electric boat, just like a house, is the only way to go.

My first yacht had a propane or LPG stove which always gave me the creeps when lighting it. And though I never had gas leakage problems, I made damned sure all the cooking aboard my next yacht would be done in the cockpit. Not exactly practical when it was raining!

Propane has a RON of 120 and is incredibly explosive, particularly as being heavier than air it quickly accumulates in a bilge. At 98 RON the butane used in portable canister camping stoves is way safer and far faster than alcohol such as meths which has a much lower calorific value per litre than butane.

A large capacity alternator can always be fitted to an auxiliary diesel for powering 240V appliances via an inverter. Trouble is, running a galley hotplate or electric kettle will not place enough load on even a 40hp diesel, resulting in cylinder bore glazing down the track through excessively early fuel injector spray.

The answer is a compact diesel genset and one that’s water-cooled for reliability. And among the better units available is Nanni Diesel’s QFM3.5M, first released in Aus at the 2011 Sydney boat show as the QF3.5.



The Nanni QFM3.5M produces a maximum of 3.5kVa (Volts x amps x 1000) with a power factor (PF) of 1.0. This means direct resistive loads such as incandescent and halogen lights and simple bar radiators.

However, appliances such as fridges, air-con units, drills, sanders and planers have a PF of around 0.8, so if powering these, the Nanni QFM3.5M can handle up to 2.8kVa. In reality these appliances have way higher starting currents than normal operation, so this genset can only just handle a compact air-con unit. Even a 500lt fridge that normally draws 260 Watts can draw up to ten times that amount when starting.

A single galley hotplate draws around 1500W on high and a cordless kettle 2200W with a PF of 1.0, whereas a full-sized microwave draws 1400W with a PF of 0.8, regardless of whether it’s sold as a 650 to 780 Watt unit. Contrary to many beliefs the magnetron that produces the microwaves is still relatively inefficient, though still way more energy efficient than using a stove hotplate because of its rapid cooking ability.

The QFM3.5M has a Nanni Diesel N1.7 diesel that develops a maximum of 6.1hp at a steady 3000rpm from its 279cc single-cylinder direct-injection German-made Farymann powerhead. This gives a 30 per cent reserve capacity between maximum alternator load and what the engine can develop, so even under maximum load the engine should have a long lifespan.

The Italian-made Coeimo alternator is regarded in the power equipment industry as one of the best available. The voltage range of 219 to 241 is acceptable for all Aus mains electricity appliances which need 230V and 50 Hertz or cycles per second. Voltage stabilisation is also good meaning that switch mode power supply appliances can be run, such as compact fluoro lights and battery chargers. Not sure about laptops though!

The Nanni QFM3.5M is enclosed in a sound-reduction casing and measures 590mm long, 405mm wide and 515mm high with a dry weight of 105kg. Even at three metres the noise level is 60dBA, equivalent to a 90hp four-stroke outboard idling three metres away from the operator. You sure won’t get tinnitus from this unit!

Nanni Diesel QFM3 5M

Nanni Diesel Australia supplied me with a maintenance manual for this genset. The first oil and filter change are at 20 hours then every 200 hours or annually when the engine thermostat and fuel pre-filter should be replaced. Valve clearance adjustment is every 400 hours or two years.

If the genset is used infrequently I recommend changing the oil and filter every six months. An API (American Petroleum Institute) CD diesel oil with an SAE 15W40 rating is recommended, as the lower 15-weight is needed to quickly lubricate the overhead valve rocker gear when the engine starts from cold.

During the 28 years I’ve been evaluating gensets I’ve found all respond best to some TLC. This means warming the genset up for at least three minutes from cold before applying load and progressively increasing loading. I also suggest disconnecting electrical loads at least two minutes before switching off. And being a fixed-rpm unit I recommend running the genset with at least 2kVa load on it continuously to prevent engine damage from insufficient load.

Nanni Diesel recommends opening the shroud access panels and priming the diesel fuel pump if the engine has not been used for several months. The oil sump level should be checked and the fuel feed valve and cooling water seacock opened. If the unit won’t be used for a while don’t forget to turn off the fuel feed and with this unit, close the cooling water seacock as some of the Chinese-made cocks can fail prematurely from electrolysis.



While I still don’t like single-cylinder diesels as auxiliary engines, they’re fine in gensets. Flexibly mount the QFM3.5M and you’ll hardly know it’s there, apart from the big box dominating your bilge. Being a Nanni Diesel it should give years of trouble-free operation and it makes your boat way safer than using LPG or even butane for cooking.

For more information on this unit, contact Nanni Diesel New Zealand, phone (09) 309 0048, email: or visit




52dBA at 7m

56dBA at 5m

60dBA at 3m






TYPE Single-cylinder diesel

RATED HP/kVA 6.1/3.5 at 3000rpm

TORQUE 784Nm at 1800rpm


BORE X STROKE 82 x 55mm

WEIGHT 105kg (dry) with sound-reduction enclosure


Originally published in Trade-A-Boat #247, November / December 2014. Why not subscribe today?


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