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Old 05-11-2008, 12:10   #1
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mmckee1952's Avatar

Join Date: Oct 2007
Location: Cobbs Creek, VA
Boat: 1976,Irwin 37 CC, Blue Bayou
Posts: 270
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Perkins 4-108 Alternator problem

This last weekend after a non eventfull motor of about 3hr's to an anchorage for the night, we started to get underway the following morning. When I got the motor running I noticed that I didn't have any voltage output from my alternator
on the control pannel also, at this time the motor's RPM's started to surge up and down all over the place. I thought I was going to have a run away on my hand's but after about 3 min. the alternators pannel showed the correct voltage and the motor ran fine. This is the first time this has ever happened and it took me by surprise to say the least. Could the lack of 12 volts coming from the alternator have caused this? On the way back, 2hrs to our marina everything was alright. Any thought's out there? I know the first thing I need to do is check the connections on the alternator and other places, but it sure was funny (not at the time) how the motor surged and all.

Take Care,

Mike & Glinda
s/v Blue Bayou
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Old 05-11-2008, 12:45   #2
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Join Date: Mar 2006
Location: Tampa Bay area, USA
Boat: Beneteau First 42
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What kind of alternator are your running and is the regulator internal or external?

We also have a Perkins 4-108 and had a similar experience with our externally regulated 105 Amp alternator. The matter proved to be the regulator which we had to replace. Subsequently, we've had similar experiences on a few limited occasions but only when the batteries are fully charged, in which case the regulator (a Balmar AR-5) seems to repeatedly turn the Alternator on and off causing the Engine RPM to seem to surge up and down. Imposing a "drain" on the batteries--e.g. flipping on a few lights, turning the thermostat on the 'frige down to kick the compressor on and/or running a cycle or two with the LectraSan in our forward head--seems to clear the matter up.


s/v HyLyte
"It is not so much for its beauty that the Sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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