[C320-list] Alternator Fuse on Yanmar 3YM30 powered 320 MK II

[Jack Brennan]

I didn’t see the start of this thread, but I think I can contribute.

These stock alternators are aftermarket, not made by Yanmar, despite the sticker. Do some searches on the Internet. You can buy a 50 amp for $120 or so. There might be 80s out there, too. The same one with the Yanmar sticker will cost you $800.

Even though it seems illogical, there’s not a large difference between the 50 and 80 stock units unless you have a huge battery bank. 

That’s because the charging rate slows as the alternator heats up and because the acceptance rate slows for your batteries as they fill up. You might start at 80, but you’ll soon be at 50 or 30 or less. 

My alternator is not fused. It is wired to the common pole on the switch. If you switch through off when the diesel is running, you kill the alternator.  I have 200 amp fuses on the positive battery posts to protect from short circuit and fire.

Jack Brennan
Sonas, 1998 Catalina 320
Tierra Verde, Fl.



Sent from Mail for Windows 10

From: Stephen Cox
Sent: Wednesday, March 17, 2021 11:35 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Alternator Fuse on Yanmar 3YM30 powered 320 MK II


> 
> Hopefully someone with a MK II hull will come along and 
> confirm.  I don't
> believe the stock alternator is fused on a  320.    I believe on later
> model 320s there is an 80A breaker (or maybe a fuse)  located at the
> battery combiner/selector switch.  

I haven't found any fuses for the stock alternator on my C320 MK II and neither is there any fuse or circuit breaker on the
electrical panel.  

There are Limitron KTK-40 inline fuses (40a) near the batteries on the positive cables from the mains charger.


Stephen Cox
Tegwen #1141