Any idea how I tell what model/capacity this alternator is?

[Chris & Lenore]

The previous owner said it was replaced in 2004 but doesn't remember what it was replaced with. A commercial marine electric did the work but they don't have records going back that far. The engine is a Yanmar 3GM30F. I photographed all around the alternator with my camera phone but can't find any model or serial numbers.
It's a Hitachi from the symbol on the back casting. Maybe the connection configuration is a clue? The fan and pulley are all painted the same colour but there is no paint internally, so I don't think it's a rebuild. The regulator is internal and it does have a "sense wire" (connected to +).

Here are a few pics.

Chris

 

[Chris & Lenore]

After looking at images on Google for a good hour - it looks like either a 55 or 80 amp unit. There are subtle differences in the castings which don't match the OEM 35 amp unit. The odd thing is that mine has that yellow wire out the back. There were a few of the 80 amp units that had a pigtail but they all came from the side of the rear casting.
No fuse on the output either - goes straight to a diode isolator and then to the three batteries.

Chris

 

[Maine Sail]

Should be a silver & green label on the case. You may need to remove it to see it. Will be something like LR180...... etc......

 

[Chris & Lenore]

No sticker....

Photographed all around it - managed to see every inch and no sticker or any other markings. At least I know it a Hitachi, but that's about all.

Chris

 

[Stu Jackson]

Re: Any idea how I tell what model/capacity this alternator

Chris,

IIRC, there were only a few sizes made for those engines anyway, and were pretty hard to find anything else that would fit. Have you measured the output and a discharged bank?

Are you also aware of the Hitachi temperature limiting inside the alternators? If not, I'll post Maine Sail's text about it.

 

[Chris & Lenore]

Hi Stu,

I think it will come down to an ammeter and a discharged battery. I'm pretty sure I have a 100 amp shunt from a previous project that I can use.

No, I am not aware of the temperature limiter that you mentioned - if you can point me Maine Sail's article, that would be great.

Speaking of Maine Sail, that reminds me I need some more Bed-it tape for this "new to us" boat. Everything needs to be re bedded (or properly bedded).

Chris

 

[Stu Jackson]

Re: Any idea how I tell what model/capacity this alternator

Chris, here you go, good luck:

Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorbtion voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

http://forums.sbo.sailboatowners.com/showthread.php?t=125392

and this, too:

http://www.cruisersforum.com/forums...d-smart-regulator-instal-question-125843.html