Yanmar 3YM30 Alternator problem

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syoun10

syoun10

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Jan 28, 2012
101
2006 Hunter 33 Santa Barbara
I'm sorry to post another question asking for help, but I'm having electrical problems on my 2006 Hunter 33 with Yanmar 3YM30, and there is such a gathering of experts here that seem to always have good advice!

With my battery about 60% charged (according to my recently installed Xantrex Power meter), When I start the engine, at 1500RPM, I get between 40Amps and 18Amps going into the battery. The amperage is swinging wildly between these limits. After a few minutes at varying RPM, the charging current drops to swing between 24 Amps and 6 Amps, occasionally falling to -1.5 Amps (a few fixtures are drawing power). The voltage on the battery varies between 12.1V and 12.7V (to low, it seems to me).

Do you think this indicates the alternator is shot? Obviously it has the capability of producing 40 Amps (at least instantaneously) but the wild swings in current and the apparent drop-off in current after a few minutes are a problem! Could it be that there is a temperature limiting circuit that degrades the alternator output if it gets too hot (it certainly does feel warm, but I don't know if too warm)?

Any thoughts and comments would be welcome.
 
seadaddler

seadaddler

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Dec 19, 2006
5,832
Hunter 36 Punta Gorda
Batteries

How about your batteries what is the condition of your batteries and are the connections clean,maybe your batteries need replacing and the alternator is trying to charge them and they are not holding a charge proberly.
I already changed my batteries 2 years ago on my 07 H-36,after hearing from guys here that are more expert at this can advise but I would do a battery testing and also see what you have drawing from them.
Nick
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
Just a guess

I would look for a bad/loose/corroded connection somewhere, or possibly a bad battery. From what I have seen and heard, the batteries Hunter used in those boats were pretty much junk. If it does turn out to be the alternaor, I think that boat came with a 60 amp. You can replace it with an 85 amp unit, from one of the parts houses, for around a hundred bucks, and get a lifetime warranty as well. Good luck on finding this gremlin.
 
syoun10

syoun10

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Jan 28, 2012
101
2006 Hunter 33 Santa Barbara
Nice N Easy said:
I would look for a bad/loose/corroded connection somewhere, or possibly a bad battery. From what I have seen and heard, the batteries Hunter used in those boats were pretty much junk. If it does turn out to be the alternaor, I think that boat came with a 60 amp. You can replace it with an 85 amp unit, from one of the parts houses, for around a hundred bucks, and get a lifetime warranty as well. Good luck on finding this gremlin.
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Nice N Easy-

Thanks so much for your response. I'm looking for more info... I researched some time ago (for a different problem) & a replacement alternator seemed to be more like $800! For $100 I'd willingly get a bigger one. So can you give me a specific lead for a parts house that has one for $100. Is it a made for marine use (ignition protected) If not, do you think that is important?
 
seadaddler

seadaddler

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Dec 19, 2006
5,832
Hunter 36 Punta Gorda
Look here

Look in the forum search for a good price on alternators on E-bay.
In the old days you maybe find a alternator for maybe $100 but to day nothing is cheap unless you get lucky and find a super deal some place.
I think if you go to a rebuilder shop that rebuilds starters and alternators they could first bench check your alternator for you before you even buy a new or rebuild,I have done this many times back in the day when repairing all my trucks and cars and recently my son had a alternator on his car for i think $195.00.
When my batteries went bad on my 07 H-36 they just kept charging for ever and ever and found out they were going going gone,Hunter does not send boat with batteries to dealers and instead the dealer adds the batteries deepending on what you asked for when ordering unless you said nothing and than they put in what they decide and that was what I got in my new H-36 and they were 2 4D's exide batteries and no start battery,now I have 4- T-105's Trojan's aand they are great and I added a very small start battery from Sam's for starting my Yanmar and Gen.
Get the alternator bench checked and than maybe the batteries also is a good time to do it all.

Nick
 
kloudie1

kloudie1

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Nov 6, 2006
10,217
Hunter 34 Mandeville Louisiana
Like N&E says, sounds like a loose connection or a bad connection.. Don't forget to check the grounding path as well as the "hot" path.. Could be anywhere in the alternator circuit.. Like Nick says, you can get the alternator checked at an auto parts place or a rebuild shop so that is quickly eliminated.
 
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