Perkins M115T - 4 Engine Room Ventilation

TPD1317e Chapter 4
Page 23
Engine Room Ventilation
The engine room must be ventilated for two reasons:
To supply the engine with air for combustion.
To provide a ow of air through the engine room to prevent an excessive temperature build up, which
may cause components such as the alternator to overheat.
In most applications in temperate climates, the engine will draw air from the engine room. If this is the case
then, as a rough guide, it can be taken that every horsepower produced by the engines requires, as a minimum,
0.25 sq.ins. of vent area. If the boat is likely to be used in hot climates, and if engine room ventilation fans
are tted, then a vent area of 0.5 sq.ins. per horsepower should be provided, (see the table below). Wherever
possible a ow of air through the engine room should be encouraged by using forward facing intake vents to
take advantage of ram airow, together with other vents to allow hot air to escape.
With an effective ventilation system the engine air intake temperature will be no more than 10 Centigrade
degrees higher than the outside air temperature.
Minimum cross section of air duct per engine
Model For hot climates For temperate climates
M300Ti 900 sq.cm (140 sq. ins) 450 sq.cm (70 sq.ins)
M265Ti 800 sq.cm (125 sq.ins) 400 sq.cm (60 sq.ins)
M225Ti / M215C / M185C 600 sq.cm (100 sq.ins) 300 sq.cm (50 sq.ins)
M135 / M130C 300 sq.cm (50 sq.ins) 150 sq.cm (25 sq.ins)
M115T 350 sq.cm (54 sq.ins) 175 sq.cm (27 sq.ins)
M92 / M92B 280 sq.cm (43 sq.ins) 140 sq.cm (22 sq.ins)
The air entry vents should be situated where spray is not likely to enter them and some form of water trap is
desirable (see gure 1). Preferably the air ducts should reach the engine compartment at the sides of the hull
so that water will fall into the bilge.
When the engines are shut down after a run at high output in high ambient temperature conditions, it will be
found that very high air temperatures will build up in the engine compartment. In boats with open cockpits this
is usually of no real consequence but if the engines are mounted below a wheel house, then unpleasantly
warm conditions may result. In these circumstances engine room ventilation fans are benecial, preferably
arranged to exhaust air from over the engine.
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