Breaking In A New Outboard Motor Engine.

Breaking In A New Outboard Motor Engine.

Breaking In A New Outboard Motor Engine, involves running the engine under light load for at least two or three hours.

Note: ‘Breaking in’ is often called ‘running in’.

These small engines, made from aluminium alloy, break in rapidly but it is probably best to not operate the new outboard motor at full load until several hours of running has passed. I say ‘probably’ as the experts don’t really seem to agree and I advise caution. Although new manufacturing techniques are producing engines with consistent tolerances and better surfaces on moving parts, notably the cylinder walls, some break in period would still seem to be a sensible procedure.

Breaking In A New Outboard Motor Engine – why?
A new engine is broken in mainly to improve the contact between the piston rings and the cylinder walls. There is no one method of breaking in but I suggest two things:

1: Operate the engine under light load for its first few hours of operation.

2: Use only a basic engine oil (except for two stroke engines) as high performance engine oils such as synthetic or semi-synthetic oils are so effective they will prevent any wear and thus prevent any ‘break in’.

3: For two stroke engines I suggest mixing a cheaper 2 stroke oil – and more of it – in the petrol for the first few tanks of fuel. Something like 25:1 for a start and then move on to 30:1, 40:1 or even 50:1 (Where the handbook specifies this.) If you are going to run on a lean oil mix you need a top grade two stroke oil and typically this would be any two stroke oil graded as TC-W3.
(Read this:

Air cooled 2 stroke outboard motors do not need marine two stroke oil because they run hotter than water cooled two stroke outboard motor engines.

What Happens In Break In: A cylinder wall is not perfectly smooth but has a slight roughness to help oil adhesion. As the engine is first used, the piston rings that seal between the pistons and cylinder walls, work in and improve their effectiveness.  If the piston rings do not bed in the engine may smoke as excess oil will find its way into the combustion area and the exhaust.

(Comments appreciated)

A rather large marine diesel engine..

Breaking In A New Outboard Motor Engine

80,080 kW (107,389 hp) marine diesel engine


Bore: 960 mm
Stroke: 2,500 mm
Displacement: 1,820 liters per cylinder
Cylinders: 14 (24,480 Litres)
Mean piston speed: 8.5 meters per second
Engine speed: 22–102 RPM
Torque: 7,603,850 newton metres (5,608,310 lbf·ft) @ 102 rpm
Power: up to 5,720 kW per cylinder, 34,320–80,080 kW (46,680–108,920 BHP) total
Mass of fuel injected per cylinder per cycle: ~160 g (about 6.5 ounces) @ full load
Crankshaft weight: 300 tons


Thermal efficiency exceeds 50%. This means that 50% of the heat generated by burning fuel is converted to power. For comparison, most automotive and small aircraft engines can only achieve 25-30% thermal efficiency.

Fuel consumption:

At its most efficient power setting, this 14-cylinder engine consumes 1,660 gallons of heavy fuel oil per hour.


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