Instrument anomolie

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
While headed east last Thursday, over around Marianne pass, I had a bunch of instrument malfunctions. Of the three compasses on the boat, autopilot, gps and the binnacle one, I had a variation at times of 80 degrees. My first thought was some kind of magnetic interferace. I called Chuck Creel, who runs a barge through this area on a regular basis and ask if he had ever run into such a thing in this area. Not to his knowledge. I had seen a voltage reading of 16V on the gps readout. Friday morning, I changed the alternator, and all went back to normal. Talked to the alternator shop yesterday, and he says the regulator is bad. Since the alternator is new and in warranty, an easy fix and no problem. Also along with the compass readings being out of the ballpark, both depth finders quit working about this time. So, high voltage can and will do strange things.
Along the same line. Fortunately I had a spare alternator on board, so I could continue the trip, and also an extra impeller when the new on spun the hub. Point is, have spares for important stuff on you boat at all times. More important than having them, is a good working kowledge of the systems, and how to do needed repairs. There is no help out there. Having spares, and knowing how to use them, made what could have been a disaster, nothing more than a little inconvience.
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
A good tool kit is also essential. Without tools you are as helpless as you would be without spares.
 
May 11, 2005
3,431
Seidelman S37 Slidell, La.
Good point Ross

I didn't mention tools, guess I just assume that everyone carries a decent tool kit aboard. Never entered my mind that anyone would leave home without one. I guess a lot of day trippers just stay close to home, and have paid up tow boats card in wallet. I never, ever leave the dock, without spares and tools. Short of a major engine overhaul, I have parts and tools to deal with nearly any failure.
 

Benny

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Sep 27, 2008
1,149
Hunter 320 Tampa, FL
I do carry the tools but a spare alternator is not on my list for a weekend cruise. An alternator failure is not necessarily a big problem if it does not take out a battery bank or navigation instrumentation. Beware of them after-markets.
 
Dec 2, 2003
1,637
Hunter 376 Warsash, England --
What about the poor batteries? If the system voltage was high enough to overvolt the electronics then the house & engine batteries must have taken a pasting. Most boat electronics is designed to tolerate battery equalisation which gives rise to voltages of 16 v or more. Ordinarily the batteries will limit any alternator overvoltage by absorbing the extra current from a runaway alternator - for a while - unless it is a high output alternator which has an output of more than the battery max permissible charging current. People do fit these regardless of the battery capability.
I suggest an examination of both banks including a load or capacity test.
Regards,
 
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