3gm30f 55amp or 35amp alt

[Notyetsinking]

So I have ordered a rare electrical lr-155 hitachi alternator to replace the one that recently died. I didn’t have a chance to confirm the alternator as I was in a rush leaving the boat. This is a place holder fix until I am able to properly upgrade the electrical system. I didn’t realize when ordering that there was an option for a 35amp alt (why would someone spec that?). Anyway, if the alternator turns out to be a 35amp, are there any gotchas to upgrading the 35amp unit to 55amp? I am a computer/electrical engineer so the electronics are not an issue, I am just looking to make preparations.

[Notyetsinking]

Originally Posted by Notyetsinking

So I have ordered a rare electrical lr-155 hitachi alternator to replace the one that recently died. I didn’t have a chance to confirm the alternator as I was in a rush leaving the boat. This is a place holder fix until I am able to properly upgrade the electrical system. I didn’t realize when ordering that there was an option for a 35amp alt (why would someone spec that?). Anyway, if the alternator turns out to be a 35amp, are there any gotchas to upgrading the 35amp unit to 55amp? I am a computer/electrical engineer so the electronics are not an issue, I am just looking to make preparations.

Edit: I was sent a J&N 400-44130 alternator which is an 80 amp unit. I figured Rare electrical was more of a distributor but it was not at all clear who the manufacturer was. Will this alternator work?

[lateral]

As long as mounts and pulley offset are same
as hitachi you are good to go. Check pulley width
Is correct.
I fitted one of those (110A) for a short time to
my 3gm30f but ditched it in favour of Bosch 115A
off a Porsche 944 (with quick mount tweek)
that I could externally regulate easily and had forced
air cowling from outside engine rm. Previous one Hitachi clone overheated.
At 60$ I got what I paid for.

[Wotname]

Originally Posted by Notyetsinking

So I have ordered a rare electrical lr-155 hitachi alternator to replace the one that recently died. I didn’t have a chance to confirm the alternator as I was in a rush leaving the boat. This is a place holder fix until I am able to properly upgrade the electrical system. I didn’t realize when ordering that there was an option for a 35amp alt (why would someone spec that?). Anyway, if the alternator turns out to be a 35amp, are there any gotchas to upgrading the 35amp unit to 55amp? I am a computer/electrical engineer so the electronics are not an issue, I am just looking to make preparations.

Originally Posted by Notyetsinking

Edit: I was sent a J&N 400-44130 alternator which is an 80 amp unit. I figured Rare electrical was more of a distributor but it was not at all clear who the manufacturer was. Will this alternator work?

I'm not exactly sure what you are asking.

The rated output of the alternator (35/55/80 A ect) is simply the maximum current the alternator is designed to provide without overheating or burning up.

If the mechanical footprint and pulley size are suitable for the existing brackets on the engine, then you can fit any of them.

Electrically most of these alternator are internally regulated and tend to have similar wiring to the terminals however you do need to check this.

The 3GM30F has three wires connected to the alternator.
1. the B+ wire which is the output of the alternator and goes to the battery +ve usually via the starter motor terminal.
2. The Charge light terminal which goes (unsurprisingly) to the charge light on the engine instrument panel. This wire provides initial field excitation when the alternator initially spins up and also causes the light to illuminate. Once the charge lamp goes out, the alternator is self exciting and also producing it's regulated voltage.
3. The sense wire which goes to battery +ve via the key switch.

The size and state of charge of your battery bank and any other electrical loads turned on will determine the current draw from the alternator. Of course, the maximum current the alternator can produce is its rated current.

EDIT: Crossed posted with Lateral!

[Notyetsinking]

Originally Posted by Wotname

I'm not exactly sure what you are asking.

The rated output of the alternator (35/55/80 A ect) is simply the maximum current the alternator is designed to provide without overheating or burning up.

If the mechanical footprint and pulley size are suitable for the existing brackets on the engine, then you can fit any of them.

Electrically most of these alternator are internally regulated and tend to have similar wiring to the terminals however you do need to check this.

The 3GM30F has three wires connected to the alternator.
1. the B+ wire which is the output of the alternator and goes to the battery +ve usually via the starter motor terminal.
2. The Charge light terminal which goes (unsurprisingly) to the charge light on the engine instrument panel. This wire provides initial field excitation when the alternator initially spins up and also causes the light to illuminate. Once the charge lamp goes out, the alternator is self exciting and also producing it's regulated voltage.
3. The sense wire which goes to battery +ve via the key switch.

The size and state of charge of your battery bank and any other electrical loads turned on will determine the current draw from the alternator. Of course, the maximum current the alternator can produce is its rated current.

EDIT: Crossed posted with Lateral!

I am asking about the fitment, I am new to marine alternators and the whole process of working with parts that aren't OE. I am pretty handy with automotive engines, but for some reason I have psyched myself out a bit with the Marine application.

I understand the current aspects of the alternator, I am very comfortable with that. What I am not comfortable with is how the whole system will play together when a harness designed for 35 or 50 amps is brought up to 80 amps (I understand it will never be this value, but the design considerations I imagine remain the same). Said another way, a system designed to 35 amps seems like it would struggle with an 80 amp alt.

Will I need to add protections to the battery to handle this new current? Or is that more of something to be handled along with the li batteries?

[lateral]

Harness to ignition ok.
B+ alternator to battery & bat ground should be sized to 80A if it isn’t already.
Pretty sketchy details you’ve provided.
Plenty of marine alternator systems online.
Robs Collins marinehowto in particular.
Search of model # didn’t give me a picture so don’t know exactly what you are getting.LR 155 clones are all similar except for output. AFAIK.

[Notyetsinking]

Originally Posted by lateral

Harness to ignition ok.
B+ alternator to battery & bat ground should be sized to 80A if it isn’t already.
Pretty sketchy details you’ve provided.
Plenty of marine alternator systems online.
Robs Collins marinehowto in particular.
Search of model # didn’t give me a picture so don’t know exactly what you are getting.LR 155 clones are all similar except for output. AFAIK.

Here is the alternator I received:
https://www.jnelectric.com/400-44130-alternator
Yes the battery and ground cables will need to be resized, good call.

[chasfgr]

Originally Posted by Notyetsinking

So I have ordered a rare electrical lr-155 hitachi alternator to replace the one that recently died. I didn’t have a chance to confirm the alternator as I was in a rush leaving the boat. This is a place holder fix until I am able to properly upgrade the electrical system. I didn’t realize when ordering that there was an option for a 35amp alt (why would someone spec that?). Anyway, if the alternator turns out to be a 35amp, are there any gotchas to upgrading the 35amp unit to 55amp? I am a computer/electrical engineer so the electronics are not an issue, I am just looking to make preparations.

35 amp is the standard size alternator supplied with smaller Yanmar motors.
Totally inadequate for a modern sailing cruiser.
In final analysis it boils down to what power your belt can transmit - the 35mm belt on a Yanmar - in the HD version will run an 85-amp alternator, but not a 155amp one.

The second boundary is the size of alternator you can mount, on Yanmars it's a short chassis model.
I ended up ditching the Hitachi alternators - all of which burnt out and ended up with a Lucas 105 amp unit specially wound for ambulances and other emergency service vehicles, this has external and internal fans - one point you'll need to upgrade the diameter of the feed wire. The standard one overheated, increased resistance and resulted in a vicious downward spiral.
The driven pulley is smaller than the Hitachi and machined from solid, increasing alternator rpm and cooling, the belt is an HD belt with internal serrations and twice the depth of the usual Yanmar belt.
I did have a smart external regulator - found that a waste of time as the Lucas internal regulator was far superior.

[caffel]

Your posts drift from 35 amps up to 80.
I suggest that an 80 may require upsizing the belt width and tension.
CA

[lateral]

Depends what life you want out of your belt.
At 50% SOC and 110A——>60ish in first hour I’m getting 100+ hrs out of a single gates green stripe. I designed my own tensioner to do a belt change in a couple of minutes. Changing my setup to serpentine or double wasn’t an option.
Max 80A you should easily treble that life. Also I suspect the thermistor will derate the output of that alt promptly as it heats up. If it’s anything like the IR in the
Hitachi.
Anyway, it’s only a stop gap. You’re going Li aren’t you? Just match pulleys and move on.
Rule of thumb, < 90 Single, >90 double or serpentine I’ve heard. I use the standard yanmar belt size on gm series and ignored that.

[Notyetsinking]

Originally Posted by caffel

Your posts drift from 35 amps up to 80.
I suggest that an 80 may require upsizing the belt width and tension.
CA

Can you elaborate on 'Your posts drift from 35 amps up to 80'?
Would the upsized belt be needed if moving from either the 35amp or 55amp? What is the general belt sizing recommendation per alt output?

[Notyetsinking]

Originally Posted by lateral

Depends what life you want out of your belt.
At 50% SOC and 110A——>60ish in first hour I’m getting 100+ hrs out of a single gates green stripe. I designed my own tensioner to do a belt change in a couple of minutes. Changing my setup to serpentine or double wasn’t an option.
Max 80A you should easily treble that life. Also I suspect the thermistor will derate the output of that alt promptly as it heats up.
Anyway, it’s only a stop gap. You’re going Li aren’t you? Just match pulleys and move on.
Rule of thumb, < 90 Single, >90 double or serpentine I’ve heard.
Anyway, I motor as little as possible.

Yes it is only a stop gap, though it will likely be a year or two before I move to LI. The boat is a racing sailboat, and I currently don't even have the option to charge the batteries from shore power. Even though I can sail very well upwind in 5knts, I sometimes need to run the motor to make sure the batteries get charged. I am in the process of redesigning the electrical system, and immediately need to replace the 2 house batteries (they also died, probably related). Annoyingly, LI isn't in the budget for that in tandem with the full electrical system. The lottery has never looked more appealing

[lateral]

Yeah, hitachi’s murder batteries with their ir’s.
Dumbest doorstop ever, esp 35A.
If you want higher output , cheap, minor mod to align
(10mins) that you can use the factory IR or VERY easily convert to ER, with the option of ducted cold air as well.
https://www.ebay.com/itm/23401482645...cAAOSwpb1gpDTt

Cheaper than your clone and way more versatile.
When I do the Li conversion (too- haha) I have a second One to replace the compressor with.
Two MC 614’s derating to 90A each.

[chasfgr]

Originally Posted by caffel

Your posts drift from 35 amps up to 80.
I suggest that an 80 may require upsizing the belt width and tension.
CA

I'm sorry you're confused.


Short chassis alternators, as used by Yanmar, come in various outputs from 35 amp to 155 amp.
I have used about 5 different alternators with various outputs without changing the belt section.
Hitachi produce 35amp and 55amp output alternators, the original post was asking which of the two the poster should fit.
I'd suggest neither, as there are more powerful, less expensive and, in my experience, more reliable alternatives available.



My current 80 amp alternator has been running perfectly for the last 20 years, in the Med, using the heavy duty belt, and charging 400 ah of batteries. I have NOT changed the belt section, but can confirm that with a larger output alternator belt wear was significantly higher.
Hitachi produce either 35amp or 55amp output alternators, others produce a wider range of power outputs in the same size and mounting.

My experience of the Hitachi models has been unsatisfactory, due to overheating and run bearings, under heavy load.

Lucas, Balmar, Rhone Poulenc and many other companies supply alternative short-chassis alternators, usually less expensive and frequently more sturdy than the two Hitachi models.


The necessary alternator output can be worked out by the daily use aboard, 35amp, more than adequate for a workboat is too little for a cruiser spending time at anchor without shorepower and will probably be between 70-110 amps.


Perhaps this elucidates my original post

[GordMay]

Increasing alternator output, above the OEM design, causes increased side loading of the water pump, alternator, bearings, and drive belt, and increased demand on the engine [motive power], beyond the engine’s original design parameters.
As a general rule of thumb:
• single 3/8" v-belt supports up to approximately ± 70 amps maximum
• single 1/2" v-belt supports up to ± 90 amps
• double 3/8" v-belts supports up to ± 140 amps
• double 1/2" v-belts supports up to ± 300 amps
• single 8 groove serpentine belt supports up to ± 300 amps