Nanni Diesel N2.14 marine engine review

The Nanni Diesel N2.14 makes life under power more pleasant while not adversely affecting the fore and aft hull trim of an old cruising yacht.

Some classic yachts never die. Full-keel yachts such as the Compass 28 and Clansman 30 may be slow by current design standards but remain good sea boats.

Trouble is, when these yachts were new, they were usually powered by eight and 12hp Yanmar marine diesel engines – wonderfully reliable but, being singles, oh so rough. Every yacht I’ve sailed that was powered by one of these visibly shook the rigging at various revs and really encouraged the owners to sail everywhere they possibly could. My flab didn’t like the attention it got!

Because of their easily driven hulls, yachts make great displacement powerboats. Sure, cockpit space ain’t like a cruiser’s but who cares, when way better fuel efficiency is possible. And out on the ocean give me a yacht every time. Yachts work through seas; cruisers just bash the hell out of them.

Nanni Diesel N2.14

So what to fit when the old single is ready for the deep six? One answer is Nanni Diesel’s little twin-cylinder N2.14 marine diesel engine, designed to make life under power more pleasant while not adversely affecting the fore and aft hull trim of an oldie like the Compass or Clansman. In fact, with a mechanical gearbox and despite having heat exchanger cooling, the Nanni Diesel N2.14 marine engine is 20 per cent lighter than the 331cc Yanmar SB8, which develops 7.9bhp at 3200rpm, and a whopping 33 per cent lighter than the 510cc, 11.8bhp at 3000rpm SB12, both of which use raw (sea) water cooling. Of course, these engines have manual start back-up but with their 23:1 compression ratios they were designed for bodybuilders.

The Nanni Diesel N2.14 marine engine has a cast-iron cylinder block and head with a gear-driven camshaft operating overhead valves via pushrods, in a simple two valves per cylinder design. The seawater pump is driven by the camshaft while the freshwater cooling pump is run by a V-belt that also drives the massive voltage-regulated 70amp alternator. With typical French logic, the drive belt is exposed. The 23:1 compression ratio effectively wipes out any chance of hand starting – not that Nanni Diesel fits such a device. The French sure know how to save a guy’s ego!

Engine maintenance and servicing

The alternator, starter motor and canister oil filter are all to port while the fuel sedimeter/bleed pump is at the forward end of the engine, where it’s instantly reachable. Even the starter motor is well above the engine bearers and thankfully the oil filter is mounted on its side so replacing it won’t cause oil to dribble down into the bilge. However, the sump oil evacuation pump pick-up is at the forward end of the sump so with the engine having an eight to 10-degree installation angle, removing all the old oil would be a real challenge. Fortunately the sump holds a reasonable 1.9 litres and can absorb a fair amount of dilution from piston ring blow-by between oil and filter changes.

Nanni Diesel recommends using a specific SAE 15W40 diesel oil for all climates and I suggest changing the oil and filter every 100 hours or annually, as the biggest problem with yacht auxiliaries is that they don’t get enough running hours. At least with freshwater cooling holding coolant temperatures at around 80 degrees there won’t be anywhere near as much condensation in the sump as in a seawater-cooled engine that runs at around 60 degrees – that dilutes the oil, and the condensation leads to internal corrosion that can really damage a marine engine.

Nanni Diesel torque and fuel consumption

Complete with mechanical gearbox, the N2.14 is 593mm long, 464 wide (380 between engine bearers) and 486mm high. In comparison, with ’box the SB8 measured 637x498x607mm and the SB12 670x520x678mm. This means there would be heaps more space between the engine and companionway for maintenance or servicing, such as removing the rocker cover to check valve clearances. Even installation and removal for overhaul or repowering would be easier.

The compact A4 instrument panel has an analogue tachometer rated to 4000rpm (thank heavens it’s not 5000) with a digital display of engine running hours. There’s the option of key switch or starter button and warning lights are fitted for low oil pressure, engine overheat, water in fuel filter and battery charging failure.

As with all mechanically injected engines, the Nanni Diesel N2.14 marine engine should be ‘worked’ to prevent cylinder bore glazing, though Kubota’s E-TVCS indirect injection system with its high air/fuel burn efficiency should reduce that. I don’t recommend running the engine continuously more than 200rpm below the maximum torque band, while in head seas the maximum rpm should be limited to 3000 to 3200rpm to avoid the risk of overloading the engine.

The Trade-a-Boat verdict

Although the Nanni Diesel N2.14 marine engine lacks the hand-start back-up of the old singles, this is more than compensated for by the smaller dimensions, lower weight, more efficient running of a freshwater-cooled engine and, of course, tolerable vibration levels. The fact the engine has a Kubota base is great for spares availability, something all cruising yachties need to take into account when buying a new auxiliary engine.

Visit: Nanni Diesel New Zealand

Nanni Diesel N2.14 sea trials

RPM	Max torque (NM)	BHP absorbed by prop	Actual L/h
1600	25	0.5	0.4
1800	27	0.9	0.6
2000	28	1.5	0.8
2200	29	2.1	1.0
2400	30	3.0	1.2
2600	30	4.2	1.5
2800	30	5.5	1.8
3000	29	7.2	2.1
3200	28	9.0	2.5
3400	27	11.5	3.0
3600	26	13.8	3.6