Findings about alternator upgrade for Yanmar 3GM30F

[Syversens]

Hey all, so this isn't as much a question as a finding. After months of research, trial and error I've finally got my alternator to output what I believe is correct voltage.

This all started months ago when our small standard 35amp alternator stopped working on our Yanmar 3GM30F. I started looking for a new alternator and for those who have shopped around you've probably seen them from internal regulated $70 to multi stage $1000 systems from a crazy amount of sources and manufacturers.

When talking to local Yanmar shop they suggested upgrading to the 3YM alternator that's has higher amp output and they quoted $350. I went online with this information and sourced one for $80. The Yanmar shop warned me that the frame would be a bit bigger but everything should be a direct fit. So, got the new alternator and installed it this winter/spring, it does fit but having a bigger frame meant the alternator would not "swing" as close to the motor as the smaller frame so in order to get belt on I have to remove alternator completely, not ideal but I'm ok with this for now. With a slightly longer belt I think it might slip on there so I'll look into that later.

OK, so new alternator installed, all well but I'm just getting 13.8V but the spec said 14.3 so I started looking at online resources. I've concluded that 14.2-14.4 is the best range so after surprisingly slow charging on a few long trips I decided to take it to an alternator shop for testing. It tested at 70 amp, which is spec and at 14.3V, also spec. The alternator shop suggested to make sure connections are good as the hitachi alternators have small studs and proper connection is critical. they recommended adding washers on both sides of the cable connector.

Reinstalled with washers and saw voltage go to 14.0V, realizing I was close I started looking at connecting directly to house with sense and +/- instead of using the Yanmar harness. After more research on this I wired the top of the T (sense) directly to +, the bottom of T to the plug in the Yanmar harness and installed 2 gauge marine cable for both - and + directly to house instead of starter.

Started up and immediately saw voltage between 14.3 and 14.4, yay!

Sorry for the long rant but I this was one of those aha moments and improvements that seems well worth it with small investment. I have no long term experience with this setup and definitely not claiming to be expert on alternators but thought I'd share my experience and findings. I would recommend to take alternator seriously and know your systems, I ignored this for years, little did I know....

Also I certainly pay more attention to my charging system after all this, it's important feature for our boat as we unfortunately consume far too many amp. hours.

 

[gleason99]

Hey all, so this isn't as much a question as a finding. After months of research, trial and error I've finally got my alternator to output what I believe is correct voltage. This all started months ago when our small standard 35amp alternator stopped working on our Yanmar 3GM30F. I started looking for a new alternator and for those who have shopped around you've probably seen them from internal regulated $70 to multi stage $1000 systems from a crazy amount of sources and manufacturers. When talking to local Yanmar shop they suggested upgrading to the 3YM alternator that's has higher amp output and they quoted $350. I went online with this information and sourced one for $80. The Yanmar shop warned me that the frame would be a bit bigger but everything should be a direct fit. So, got the new alternator and installed it this winter/spring, it does fit but having a bigger frame meant the alternator would not "swing" as close to the motor as the smaller frame so in order to get belt on I have to remove alternator completely, not ideal but I'm ok with this for now. With a slightly longer belt I think it might slip on there so I'll look into that later. OK, so new alternator installed, all well but I'm just getting 13.8V but the spec said 14.3 so I started looking at online resources. I've concluded that 14.2-14.4 is the best range so after surprisingly slow charging on a few long trips I decided to take it to an alternator shop for testing. It tested at 70 amp, which is spec and at 14.3V, also spec. The alternator shop suggested to make sure connections are good as the hitachi alternators have small studs and proper connection is critical. they recommended adding washers on both sides of the cable connector. Reinstalled with washers and saw voltage go to 14.0V, realizing I was close I started looking at connecting directly to house with sense and +/- instead of using the Yanmar harness. After more research on this I wired the top of the T (sense) directly to +, the bottom of T to the plug in the Yanmar harness and installed 2 gauge marine cable for both - and + directly to house instead of starter. Started up and immediately saw voltage between 14.3 and 14.4, yay! Sorry for the long rant but I this was one of those aha moments and improvements that seems well worth it with small investment. I have no long term experience with this setup and definitely not claiming to be expert on alternators but thought I'd share my experience and findings. I would recommend to take alternator seriously and know your systems, I ignored this for years, little did I know.... Also I certainly pay more attention to my charging system after all this, it's important feature for our boat as we unfortunately consume far too many amp. hours.

Hello, could you post some pictures of the wiring you did, that would really help

 

[Syversens]

Good idea, will do!

Honestly I wasn't sure if I should post about this since I'm no expert and there seem to be infinite ways to set it up, and mess it up... I'll post some pictures of my alternator, wiring, perhaps a wiring diagram ASAP.

 

[mz4wheeler]

Reinstalled with washers and saw voltage go to 14.0V, realizing I was close I started looking at connecting directly to house with sense and +/- instead of using the Yanmar harness. After more research on this I wired the top of the T (sense) directly to +, the bottom of T to the plug in the Yanmar harness and installed 2 gauge marine cable for both - and + directly to house instead of starter.

Started up and immediately saw voltage between 14.3 and 14.4, yay!

Just a cautionary note here, not really knowing what you really did electrically:

The regulator controls the sense, and it is supposed to intelligently reduce charging when appropriate. If you somehow bypassed this, your alternator will do this:

1) Always crank out maximum voltage
2) Fry your batteries early
3) Overheat (alternator), followed by early failure.

If you are not charging at full capacity, it means that your batteries are OK. If you had super dead batteries most likely you'll have your 14.3 volts.

 

[Syversens]

Your caution is well warranted but I'm starting to feel comfortable with my system at this point, others should familiarize as best they can before experimenting. I'll get some pictures but most of what I did is fairly common for those wanting to connect alternator directly to house instead of starting battery for various reasons.

One thing that was a surprise to me was how big a difference it was making sure connectors are correct size and well connected. Going forward I'm going to pay far more attention to connectors than I have, specially on high amp studs... I always figured they were big so even if there's some corrosion or that what stuff, its ok... Now I'm thinking it's much more important and will be something I'll go around checking when I can. Honestly it shouldn't be a surprise and I should have known better

 

[Maine Sail]

Just a cautionary note here, not really knowing what you really did electrically:

The regulator controls the sense, and it is supposed to intelligently reduce charging when appropriate. If you somehow bypassed this, your alternator will do this:

1) Always crank out maximum voltage
2) Fry your batteries early
3) Overheat (alternator), followed by early failure.

If you are not charging at full capacity, it means that your batteries are OK. If you had super dead batteries most likely you'll have your 14.3 volts.

?????????

Voltage sensing simply tells the regulator what the output voltage is where it is connected. If the alternator is "self sensed" it is sensing the system voltage before any voltage drop and the batteries will charge considerably slower if the wiring has voltage drop like most factory systems do. Moving the voltage sensing to the battery terminals is the most accurate and leads to the fastest charging but not all alternators have this capability.

 

[Bloodline]

The comment about washers on both sides of the connector caught my eye. A steel washer is a relatively poor conductor before it begins to corrode...

 

[mz4wheeler]

?????????

Voltage sensing simply tells the regulator what the output voltage is where it is connected. If the alternator is "self sensed" it is sensing the system voltage before any voltage drop and the batteries will charge considerably slower if the wiring has voltage drop like most factory systems do. Moving the voltage sensing to the battery terminals is the most accurate and leads to the fastest charging but not all alternators have this capability.

If the sensed voltage is directly to a battery, yes, that is the most accurate. However, if you have crappy connections between the alternator and the battery, then you are essentially trying to charge a battery with a voltage drop between each bad connection/terminal.

 

[Syversens]

The comment about washers on both sides of the connector caught my eye. A steel washer is a relatively poor conductor before it begins to corrode...

I used stainless steel washers figuring they wouldn't corrode but if there is some other type of connector that would be better I'd sure opt for that. The difference with applying them was quit noticeable improvement though. The studs on this, and the original Yanmar, are tiny and the nuts that go on it are small as well. I'm still in testing phase so curious if there are better ways to connect to small bolts like this with high amp.

 

[Maine Sail]

I used stainless steel washers figuring they wouldn't corrode but if there is some other type of connector that would be better I'd sure opt for that. The difference with applying them was quit noticeable improvement though. The studs on this, and the original Yanmar, are tiny and the nuts that go on it are small as well. I'm still in testing phase so curious if there are better ways to connect to small bolts like this with high amp.

Copper or brass washers are much more conductive than stainless and would be preferred. That said the ABYC specifically prohibits the use of washers between terminal and contact point. Perhaps your lug/terminal hole was simply too large for the tiny Hitachi stud?

 

[Syversens]

that is possible but I couldn't find the correct hole/lug size to match the cable I wanted, I went with the smallest those lugs had. Also my cable is oversized to accommodate an even larger alternator should I want to go that route.

I'd absolutely prefer not to have washers there and as soon as my system is finalized I'll see if I can get better fitting lugs on there. I just went with the smallest hole for a 2 gauge lug but its still too big.

I really appreciate all the feedback everyone, I thought I was close to done but there are still improvements to be made. Strangely enough I've found this to be the simplest system on the boat, yet the one that can be tuned extensively.... well except for the sail of course