Bruce wrote: > Thanks Roger. I note that the next engine will have a 175 A domestic > alternator, so in six years they've gone from the 90 A beast on Sanity > to nearly three times that capacity. > > Looks like I'm lucky to have got the time I did out of the present > kit, though my practice of never discharging below around 12.2 V if I > can possibly help it may have something to do with it, I guess.
One thing that I should have mentioned, and it will be even more important the higher the alternator output, is to ensure you have a plentiful supply of cool (or as cool as can be obtained) air preferably delivered to as close to the alternator as possible. You need a good supply of air into your engine boxing anyway (that is a given and is ignored at your peril) but while that supply may be fine for your engine, does it waft past the back of the alternator on its way to the engine inlet? The alternator will be working hard and generating a lot of heat, if it sits stewing in an unventilated corner of the engine box you won't do it any favours. If it is possible I think I would try to bring a hose trunking in behind the alternator taken off somewhere near the baseplate where it is relatively cool. Think about an application in a typical car. On in-line engines the alternator sits to one side of the block in the airflow that comes through the radiator and other inlets at speeds of between 15 and 90 mph usually ;-)). On an East-West engine the alternator is usually in front of the block subject to similar airflow. Have you got a similarly robust supply of, no more than warm, air going to your boat alternator? On older Jags, where the alternator was still inadequately cooled due to its siting they fitted a shield around the rear of the alternator and this was fed by a flexible ducting. On the Beta cocooned engines they have a radial extraction fan which continually runs while the engine is running. This assists the drawing-in of cool air from outside the cocoon via vents. Admittedly that same air serves both engine and alternator but, I dare bet, that some boat builders make their engine box too airtight from above (for noise reduction and appearances sake) and this means that the engine is sitting in a pocket of hot air (hot air rises) only drawing in the amount required by the running of the engine. Try to run your alternator as cool as you can manage is my advice. This advice will help to extend the life of the drive belts, which are also working hard. Roger
