Keep your cool

Roger Hughes vents his engine room

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When I bought my Down East 45 schooner, Britannia, it didn’t have any engine room ventilation, either through natural aeration with cowls, or electric blowers.

The term ‘engine room’ is a bit of a misnomer on this boat because the area is 26ft long from the forward saloon bulkhead to the aft cabin. It is also 3ft 6in wide at saloon floor level, tapering 4ft 6in down to the bottom of the bilge. That is a very cavernous area and doesn’t just contain the large Perkins 4-236 main engine, but all the other machinery that runs the ship including a 6.5kw diesel generator, a five-gallon water heater, nine batteries, a large battery charger and five electric pumps. All these form what I call the ‘equipment bay.’

When everything is humming, and especially when both the generator and main engine are running together, the heat permeating through the 3⁄4in plywood cabin sole could be felt on bare feet. I once placed a thermometer in the space and after five minutes it registered 66°C (150°F), which isn’t good for the machinery or our feet!

Whether you have a large underfloor area, or a small engine compartment, it will always be beneficial to ventilate the space. All mechanical devices create heat, and diesel engines are designed to run hot, but internal combustion engines also run better when drawing cooler air, which has the effect of increasing the swept volume in the cylinders.