Shore power on your boat is a wonderful thing until you leave the dock. Once you slip the line and sail off to the distant horizon or more likely a favorite gunkhole, you’ll find yourself at the mercy of your DC charging system.
The alternator is the workhorse of that system as it’s what keeps your batteries topped off while underway, unless of course you’ve a generator. If you do have a generator then you’re a luck swab! While we covet one of our own and dream of pots of hot drip coffee and endless lights, we have to face the fact. Our alternator must be maintained to be able to provide us with the luxuries our DC system provides.
One of the more common problems is with an improperly adjusted alternator drive belt. If the belt’s too loose the alternator won’t turn fast enough to reach its maximum charging output. If you want to see about how to adjust your belts, you’ll find more information about it here.
Although it could be that you have a slipping belt instead that caused the alternator’s pulley to overheat. Have you ever seen a pulley that looks blue or purple? Chances are good that it’s suffered from continual slipping and over heating. While the over heating could cause the belt to fail early on, it could cause heat to move along the shaft and into the rotor’s magnets. Once this happens the magnets will be weakened and this will mean the alternator’s output will always be less.
Then too we all have way more electronic gear aboard than in years past and this can cause strain on the brackets. If your brackets are designed to have flex then you’re just about guaranteed to have problems. If it doesn’t fail, it will most likely move enough to cause misalignment. This will cause the belt or belts to wear down quickly and if you see belt dust then you’re likely headed towards problems. The crankshaft and alternator or the drive pulleys have to be parallel plus they have to be on the same plane or you’ll have excess belt wear.
Another problem is the wiring. Because some vibration and movement is unavoidable, you need to check that the wiring is secure, has an appropriate amount of slack and still has a good amount of life left to it. Be sure to check all the wires connected to the rear side of the alternator. Be sure the nut on the output stud is tight and locked in place with a lock washer. Loose connections often cause either arcing between the output stud and cable and could lead to overheating.
When in doubt, talk with your local boat mechanic. A little bit of help on our part with our alternator gave us a bit of a jump in power on our sailboat. Winter is a great time of year to do those never ending jobs. Don’t forget to check your sailboat’s alternator and you’ll be rewarded with topped up batteries and trouble free hours of power.
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