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orionb
orionb

Posted: Mon Aug 18, 2008 9:59am

Post Subject: Engine Bay Temperature

During the warmest summer days the temperature in the engine bay of our narrow boat reached 45deg C, our normal running temperature is 35deg C. Does this affect the life of the alternators and batteries in any way, if so what would you advise. We have normal type engine bay vents as standard. During the hot weather I did notice that the battery voltages were slightly down but resumed to normal when the weather cooled. The engine coolant temperature did not vary from normal.

Tony-B
Tony-B

Posted: Mon Aug 18, 2008 10:28am

Post Subject: Engine Bay Temperature

What are "normal type engine bay vents"? I am afraid the phrase is meaningless in an industry that seems to have no standards and several different hull styles that directly affect engine room venting. If the exhaust does not produce a black haze at high revs then the vents are probably OK, but they may still be reducing the engine efficiency by restricting the airflow. However the vents are really only there to provide a path for combustion air UNLESS its an air cooled Lister. If you want more cooling then I think you need to be looking a bilge blowers on all the time your engine is running plus suitable extra venting. If the batteries are ordinary wet cells and you check their electrolyte level regularly I doubt your batteries are in any more danger of damage than those on vehicles out in the sun in the tropics, I am far less sure about sealed batteries though because evaporation may reduce the electrolyte and thus battery capacity. The same also applies to alternators. They are normally based on automotive units and the under bonnet temperatures can get very hot - especially in the tropics. However if the cooling fan has reduced efficiency for some reason (like being the wrong hand) then prolonged high temperatures may cause diodes to fail. This is why I always advocate that the combustion air inlet vents are placed close to the BACK of the alternator so the alternator can draw the fresh cooler air through itself before venting it to the engine bay. The alternator should be designed to cope with prolonged use at maximum output (where a lot of heat is produced internally)but the modern idea of value engineering sometimes conflicts with this, so it is wise to investigate the cause of high charging currents for long periods irrespective of ambient temperature. Tony Brooks

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