Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 21-10-2015, 19:58   #1
Registered User

Join Date: Jun 2015
Posts: 28
3HM Alternator

Hello all,

I had some starting trouble on my way south, thought it was starter, then electrical, ended up being the battery. I got a new battery and now thinking it might be the alternator which is not even charging the battery. I brought the alternator to a car shop, they tested it and said it failed only putting out 11.6 volts.

So, some facts, its the new alternator type (picture below).
The previous owner did not have all the wires hocked up, some just attached to the alternator and dangling. Reading on the manual does not explain much about the R and L slots on the back, nor the wire on the side and if they have an importance.

So I wonder if the alternator is actually faulty, or if maybe just not hooked up properly. Is there a way I can test the alternator while engine is running myself on the boat?

Also anyone know which wires need to be hooked up etc to charge battery. I was told one of the slot like attachments needs to be hooked up to get the current to start moving and charge the battery.

Also if not working, anyone know a good place to get a working alternator for a decent price? The shop which tested it quoted me 450$ and said go else where for they are way too expensive, but I know yanmar parts are all expensive so who knows.

Thanks all!


ap.thoms is offline   Reply With Quote
Old 21-10-2015, 20:28   #2
Registered User

Join Date: Feb 2013
Location: WY / Currently in Hayes VA on the Chesapeake
Boat: Ocean Alexander, Ocean 44
Posts: 944
Re: 3HM Alternator

The auto electric shop would have wired it correctly for the bench test. If you have a competent shop they can be fixed/rebuilt and they should be able to tell you what wire goes where. A new one should have a diagram for installation.

darylat8750 is online now   Reply With Quote
Old 21-10-2015, 20:33   #3
Registered User

Join Date: Jun 2015
Posts: 28
Re: 3HM Alternator

I do think they tested it correctly true. But he also had no idea about where the wires go and such, and why there were so many connections on mine etc.
I would ideally not like to buy a new one, but I guess if I get it rebuilt they should know what goes where.

Anyone know any good alternator rebuild places in San Diego?
ap.thoms is offline   Reply With Quote
Old 22-10-2015, 03:08   #4
Moderator Emeritus
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 32,209
Images: 240
Re: 3HM Alternator

See pages 152 - 159
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

GordMay is offline   Reply With Quote
Old 22-10-2015, 03:23   #5
Registered User
ErikFinn's Avatar

Join Date: Feb 2011
Location: Malaysia, Thailand
Boat: Beneteau Oceanis 430
Posts: 859
Re: 3HM Alternator

There are threads about testing alternators, and also threads about replacement alternators, just try the search and you should be ok.
ErikFinn is offline   Reply With Quote
Old 30-10-2015, 16:38   #6
Registered User

Join Date: Jun 2015
Posts: 28
Re: 3HM Alternator


Thank for all for the help. I ended up getting a new one for 15$ more then rebuilding the old one and gave them the old one.

Now the problem is the wiring setup. The previous owner who set it up was missing a lot and had somethings poorly jurry rigged. That PDF is amazing! But it does not have my exact alternator, I can use the closest one, but even then I am not knowledgeable enough to know what "excite" and "aux" mean, and where those wires could go. Any help would be great.

ap.thoms is offline   Reply With Quote
Old 30-10-2015, 17:06   #7
Registered User

Join Date: Oct 2010
Location: The boat - New Bern, NC, USA; Us - Kingsport, TN, USA
Boat: 1988 Pacific Seacraft 34
Posts: 467
Re: 3HM Alternator

Boatinfo - Yanmar Service Manual for 1GM10, 2GM20, 3GM30, 3HM35

See page 12-20 (page 352 in the pdf or whatever is is). It is a drawing of the internal and external wiring of the alternator.


wsmurdoch is offline   Reply With Quote


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Yanmar 3HM 30 inti Classifieds Archive 0 11-02-2015 03:09
Yanmar 3HM replacement air filter options? Canibul Engines and Propulsion Systems 4 05-03-2014 11:33
What is the 'spring joint' on Yanmar 1gm/2gm/3gm/3hm clutch? calderp Engines and Propulsion Systems 0 21-06-2012 21:51
For Sale: Yanmar 3HM bcguy Classifieds Archive 1 05-05-2012 17:19
Yanmar 3HM Overheating drew23 Engines and Propulsion Systems 8 09-02-2010 20:31

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:56.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.