Join Date: Jun 2005
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You really need to consider which blower and how to plumb it. I've installed many for customers, but all were on big powerboats that began to suffer for horsepower in steaming hot Naples. As engine room temperatures soared, horsepower fades because the engine intake air is less dense and expands less in combustion. I used the inline 4" blowers to take air from outside and blow it straight at the engine air intakes, resulting in the engines again being able to make proper peak RPM's to get up on plane. The blowers are keyed to the engine 'run' position through constant duty solenoids. Engine room exhaust is not blown, but is ducted out from as high in the engine compartment as possible to get the hottest air first. An auxilliarly switch can be rigged on the console to cool the engine room after shutdown, but it should be either set on a timer or be accompanied by a large, annoying red light to keep you aware that it is on.
In a tight engine room, air in equals air out and engine combustion is a large part of that process, so the blowers on a big powerboat cannot possibly keep up with two big diesels at full song, though they do help performance. In a sailboat with less than 100 HP (most have 30 - 60) a single 4" blower is more than enough. I have a tendency to treat horsepower and engine health first, and engine room ventilation as a happy by-product. It still works.