Alternator not working merc 165 4cyl

I had to have my engine rebuilt and decided to have the mechanic instal a pertronix ignition as well. Took the boat out today and noticed the voltage was low (11v) while running. Multi tested the batts while running and it reads 11.5. It was charging ok before the rebuild. Any suggestions?
Thanks for any help,
Robert

Do you have the original mercury charging system or a regular type alternator??

kghost said:

Do you have the original mercury charging system or a regular type alternator??

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I am assuming the regular type. It is belt driven. The alternator only has one red wire coming from it. At least that's all I could see last night in the dark. Does it need a ground? Any help troubleshooting this?

That is a aftermarket alternator..........not factory and is a common replacement.

Those need at least 1500 rpms or so to get them to start to charge. maybe 2000.....not 10% sure.

if it was working before try revving it up in neutral at a steady 1500 - 2000 rpms and measure the voltage at the battery again.

If you are not getting at least 13.5 volts check all the connections and make sure everything is tight and clean and if still no go then remove and bring to a local starter/alternator rebuild shop for testing.

kghost said:

That is a aftermarket alternator..........not factory and is a common replacement.

Those need at least 1500 rpms or so to get them to start to charge. maybe 2000.....not 10% sure.

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Thanks. Didn't know that. Will check today. I do know that the voltmeter on the dash was showing about 11v even when running hard yesterday. It didn't do that before the rebuild and the electronic ignition convertion.

Just checked it. Ran her up to 2000rpm and it was 12.0 at the batts. is there a voltage reg somewhere also? Any other ideas other than pulling it and having it tested? Btw how long do you think it can be run before it dies if the batts are fully charged? (Electronic ignition) I was able to get through most of the day yesterday But only ran 20 miles round trip. The rest of the time I was on anchor with one battery off.

Depending on who rebuilt engine, hopefully they removed magnets from rectifier and or generator at crank. I removed my rectifier and all of its components as well as magnets so as not to be generating ac voltage after alternator kit was installed. You would have to pull off the harmonic balancer pulley at crank to be able to remove. Easier option: Some guys just cap off the wires that run to the old water cooled voltage regulator from the rectifier and leave all the guts inside. Problem being, I had a magnet break loose and it almost took out my timing cover. Also if wires were to short out and any fuel vapors were present, could be a dangerous situation. I guess I may sound a little over concerned but as you know things can happen. Anyway, I have a three wire aftermarket alternator that charges at lower rpms so as not to draw down batteries at idle for long periods of time using electronics or maybe trolling problems with the 1 wire setup. I would not suggest removing the harmonic balancer (rectifier) unless you have some mechanical skills and the proper puller so as not to damage crankshaft,balancer, and or oil seal. You will like the pertronix setup. Easier startups, smoother idle, a little more power, better fuel consumption, never gapping points,etc. Best of luck to you and Happy Thanksgiving everyone, Tom

Rsscottsdds, You snuck that last post in just as I was trying to answer some of your questions. lol, no worries If indeed you do have the original rectifier and water cooled voltage regulator, I would suggest removing both and buying an aftermarket alternator kit which should have a built in voltage regulator thus eliminating all the original oem charging system. The oem charging system is nla, and very expensive if you were lucky enough to find a used or old new part somewhere. It can also overcharge or underchage batteries and a bunch of other stuff. Some old timers differ on that thought so I will back off of that subject. Depending on what year your engine is you probably have this: You should have one pulley powered by rectifier pulley or (harmonic balancer on crankshaft if oem). If you indeed have an alternator it is either a high mount or low mount setup and should be fairly easy to determine. Also, you may have a power steering pump that is also driven by crank via belt. At most three pulleys with aftermarket setup. Probably two with oem setup. I hope this helps. Tom P.S. the water cooled oem voltage regulator should be on the port side of block towards the front. It should be mounted to block and there should be coolant lines going into it and coming out.

1. He does not have the OEM system.
He has a 1 wire aftermarket alternator.

The one wire goes to the battery directly or to the starter/battery connection.

I am not sure about a ground wire but the alt needs to be grounded. so either the brackets are not grounding to the block or you are missing a ground somewhere.

I would follow the output wire first and confirm it is where it is suppose to be and tight. in the end it has to feed the battery.

The alternator is all in one, rectifier and regulator is all built into it just like a automotive alternator.

Ran her over the weekend and never got the voltage to read over 12v. Took the alternator off to get it checked. Found a marine alternator on ebay from DB electric that looks identical to the one I have for $65. The only thing different is the amps. Its a 105amp and I think the one I had was a lot less. Any concerns using the ebay alternator? The one I have is a one wire that runs to the starter. The ebay one is a one wire as well and the bolt hole are all the same.

What did the alternator check out at?
Bert

Rscottdds said:

Any concerns using the ebay alternator?

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yeah, your output wire may not be sized to handle 105Amps. Check the gauge of the output wire and follow it to a breaker and see what the breaker is rated for - get an alt with that number.
p.s.- you may find the breaker has tripped. (red button popped out)

Why the reluctance to get your alt tested? Sure sounds like the internal regulator has crapped out. New regulator probably $5 jobber cost. An automotive electrical guy should be able to t/s it and swap a new regulator in in about 30 mins.

It was mainly a matter of convieience that I ordered one. I wasn't going to be able to get to the shop until next week at the earliest but could have the new aterator delived in a few days and do the instal that night after work The red breaker hadnt popped. I cant remember what it is but 50 or 80 come to mind. Can I run a lead directy the battery instead of to the starter (and breaker)?

I would change the output wire from the 12 or 10 gage to 8 gage.... to handle more current.

Then hook it up at the same place........the battery cables should be at least 8 but may be 6 gage....

The red round breaker is only 50 or 80 amps though. I would need to change that as well right? Do they even make them that size?

According to this web site for other "470" style motors the "fuse" that should be at the starter where the alt and battery connection are, is 90 amps so you should be OK.

If you are not sure then the one in the link is 90 amps

Other motors use a 55 amp so I don't know which you have.

Link

http://www.marineengine.com/newparts/part_details.php?pnum=MER88-79023A91


As far a needing to change it I can not say for sure.....that is just me.

If the new alt puts out more than 55 amps and you have a 55 amp "fuse/breaker" then I would say yes.

But the question is will it actually put out more than 55 amps at any given time?

Not sure.

So by going to a 105 amp alt then I would say replace it with the 90 amp one for safety sake. Odds are it will never reach 100 amp output unless you have a lot of current drawing accesories

The red reset button says 50 on it I'm pretty sure . Just going by memory but that's what I see in my mind anyway . Is there another breaker next to the starter? The red button is on the other side from the starter.

According to the ORIGINAL schematic for that motor.

The breaker is in line with the SENSE wire (red or red with purple) from the original voltage regulator mounted under the manifold with the water flowing thru it and that red/purple wire goes from the regulator to the breaker to the large starter solenoid terminal. Again it is a sense circuit not a charge circuit.

There was also a orange wire that went from the same voltage regulator (output of regulator) straight to the same terminal on the starter solenoid, Orange wire.

The orange wire was the original "alternator output". Charge circuit.

The one wire alt does away with all that so that breaker should be disconnected from the charging circuit. Maybe it was never disconnected???

The one wire alternator should feed straight to the starter solenoid???? Did your new alt come with wiring instructions?

Here is the original schematic.

I don't know how whom ever changed it, wired it?

But with a one wire alternator that breaker is not needed.

The alternator output is NOT fused or goes thru a breaker. The large fuse I pointed to in my previous post is part of the STARTING circuit if the starter or wiring is bad........So again the breaker is only there for another purpose when used in the original wiring configuration. (sense circuit)

That is my best guess......Maybe someone who has actually installed one (as I have not) may agree with me or let us both know if I ma right or wrong.

One more thing, Are you sure your battery is good?

With nothing on and putting a meter across the + and - of the battery it should read 12.4-12.7 volts STATIC with no load or drain.

Confirm that also!!! if you have a dead cell you may not get a full charging reading of higher than 12 volts........

Batts are good. Less than a year old. Charged them up before I went out a few days ago. Started at 12.6 volts. Ran for an hour and they were at 12 when I got back. If I understand you correctly the reset button is part of the starting circuit and not the charging one and that the one wire alt doesn't need a breaker or fuse? If so then all I have to do is make sure the output wire can handle the increased load. Would certainly make my life easier if true.

Yes you understand me PARTIALLY correct.

The breaker is NOT, I repeat NOT part of the starting circuit.

It is part of the SENSE circuit for the original voltage regulator. It needs to sense the voltage to operate correctly. Think of it as the same wire that would feed a volt meter for you to monitor.


The large FUSE I linked to is for the starting circuit!! (90 amp)

Think for a minute........if and when the last time you worked on a AUTO alternator...........There were three wires used on it.

1. Black wire to ground, not battery negative but a good engine ground.
2. a multi wire connection with a plug on the end, This contains the sense, exciter wires.
3. A large red wire (6-8 gage) that went straight to the battery.

Well with a ONE wire Alternator you do not have # 2 the multi wire connection. When the rpms are above 1500 the alt does the exciting itself.


You should have #1 and # 3.............

I would also trace the wires going to and from that 50 amp breaker to determine what they are connected to. If one end is connected to the old regulator if it is still mounted to the motor, and the other end is connected to the starter solenoid.......disconnect the two from each end and tape them off for good. That is a live circuit not used and could be an issue at some point.....if nothing else it will cause others confusion.....

Ahh. It's all starting to make a bit more sense now. Thanks for the responses. There are a few capped off wires close to the starter. Those are probably the ones you are talking about. I will probably install the new alt and see how things go.

Rscottdds said:

1..... It is belt driven. The alternator only has one red wire coming from it. At least that's all I could see last night in the dark.

2.... Does it need a ground? Any help troubleshooting this?

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1..... As the guys have said, if the alternator is now belt driven, the kit has been installed. Most of these kits use the Delco 10si as the replacement.

2.... The alternator chasis and mounting will provide the Negative path to the engine block, but it's always best to install what's called a "chasis to engine block" Negative cable. I'd size this identically to the charge lead.

Rscottdds said:

1.... Just checked it. Ran her up to 2000rpm and it was 12.0 at the batts.

2.... is there a voltage reg somewhere also? Any other ideas other than pulling it and having it tested?

3.... Btw how long do you think it can be run before it dies if the batts are fully charged? (Electronic ignition) I was able to get through most of the day yesterday But only ran 20 miles round trip. The rest of the time I was on anchor with one battery off.

Click to expand...

1.... The single wire 10 si requires a bump in rpm to become excited. Once excited, it will remain excited until shut down.
If at 2k rpm it did not self excite, then something is wrong with it or the charge lead.

2.... The single wire Delco 10si will have an internal regulator.

3.... As for battery run time without charging...... this will depend on the battery's health and your loads in Amp Hours.
Keep in mind that a wet cell battery left in a SOD for any length of time will begin to shorten it's life.
I'd get it charged back up ASAP.

Rscottdds said:

1... Its a 105amp and I think the one I had was a lot less. Any concerns using the ebay alternator?

2.... The one I have is a one wire that runs to the starter.

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1... Most standard and common 100 amp alternators will cut back on the charge rate rather quickly. So it's sort of a misnomer to think that these will maintain anywhere near 100 amps for any duration.
In order to get into a 100+ amp Marine alternator, we've got to spend some big money.


2... Unless this is capable of 100 amps, or even near 100 amp..... keep the original circuit. This should run to the red button circuit breaker and then down to the starter motor's solenoid terminal where the MBSS common cable connects.

hystat said:

yeah, your output wire may not be sized to handle 105Amps. Check the gauge of the output wire and follow it to a breaker and see what the breaker is rated for - get an alt with that number.

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Agreed!
If the alternator is anywhere near capable of producing a 100 amp output, this should be upsized as well as the Negative cable.

Rscottdds said:

........... Can I run a lead directy the battery instead of to the starter (and breaker)?

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I would not..... I'd keep the path the same, and upsize wire gauge if need be.
When we start circumventing the OEM, we open ourselves up to possible problems.


.

RicardoMarine said:

2... Unless this is capable of 100 amps, or even near 100 amp..... keep the original circuit. This should run to the red button circuit breaker and then down to the starter motor's solenoid terminal where the MBSS common cable connects.
.

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He no longer needs the circuit breaker......PERIOD!


The breaker is used on many configurations........it is also where the power to the ignition key comes from. In some cases it gets tapped off at the breaker, in other cases such as his this power comes from the starter solenoid.

In his configuration the breaker was between the starter solenoid and the sense connection on the voltage regulator/rectifier. (red and red with purple wires)
There was also a large orange wire which was the output of the regulator/rectifier which also was connected directly to the starter solenoid, (main charging output wire) with no breaker or anything.

Please review attached schematic above.....this was his original configuration.

So with the one wire alt all he needs to do is hook it up to the starter solenoid stud where the battery lead connects as the previous one should have been.

That is all..................

RicardoMarine said:

This should run to the red button circuit breaker and then down to the starter motor's solenoid terminal where the MBSS common cable connects.

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The schematic that you posted clearly shows what I believe to be the original charge lead going through the red button circuit breaker.
His helm power should also run through this circuit breaker, but the schematic does not show it.... at least not that I've been able to see!

kghost said:

He no longer needs the circuit breaker......PERIOD!

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If he wants to circumvent the breaker and go directly to the starter motor solenoid common cable terminal.... then yes, he certainly can.
However, the charge lead will no longer be protected.


.

I am not going to argue about this.

The schematic CLEARLY shows the red with purple wire coming from the regulator.

It then goes to the breaker and then to the starter solenoid stud where ALL the battery + wires go to.

Then there is a ORANGE wire which is the DIRECT 12 VDC out put of the regulator. This is the same wire as the ONE wire on his aftermarket alternator.

That schematic shows a DOT meaning a wire intersection between the red with purple and breaker. This intersection is where the power to the ignition comes from. So the breaker gets its 12 volts from the solenoid stud/battery connection. it passes thru the breaker then intersects and a wire goes into the large connector and feeds the ignition switch B+. if there is a current spike in the ignition circuit then the breaker will pop. NOT THE CHARGING SYSTEM.

Whom ever installed the aftermarket alternator he had before already rewired it so the power to the ignition switch is present. How, I don't know but it works.

If he installs the high current output of his new 105 amp alternator thru the breaker it will pop his first time out.

close up of the original circuit.

The conversion kit for the 470 series uses a 55 amp alternator- more than enough to keep any battery charged. Get your voltmeter out and do this simple test: connect the voltmeter + lead to the output terminal (red) on the alternator, and ground the - lead to the alternator casing. Run the engine at idle, and slowly increase the rpms. Voltage should rise to 12.9-14.9 volts, depending on the state of discharge of your battery. Anything out of these specs indicates a faulty alternator- replace it.

.........

kghost said:

I am not going to argue about this.

The schematic CLEARLY shows the red with purple wire coming from the regulator.
I see that, and have not been in disagreement!

It then goes to the breaker and then to the starter solenoid stud where ALL the battery + wires go to.
Agreed!

Then there is a ORANGE wire which is the DIRECT 12 VDC out put of the regulator. This is the same wire as the ONE wire on his aftermarket alternator.
Agreed!

That schematic shows a DOT meaning a wire intersection between the red with purple and breaker. This intersection is where the power to the ignition comes from.
OK..... I had missed the dot! Thank you.
This would be where the helm receives power that I had questioned earlier!

So the breaker gets its 12 volts from the solenoid stud/battery connection. it passes thru the breaker then intersects and a wire goes into the large connector and feeds the ignition switch B+.
Agreed.... It would first feed the helm (I.E., helm power) then via the key switch it would power the ignition system.

if there is a current spike in the ignition circuit then the breaker will pop. NOT THE CHARGING SYSTEM.
If the breaker trips, continuity "through" the breaker is disrupted!
If the charging circuit also uses this breaker, please provide an explanation as to how the alternator charge would NOT be disrupted IF the breaker was to trip!


Whom ever installed the aftermarket alternator he had before already rewired it so the power to the ignition switch is present. How, I don't know but it works.

If he installs the high current output of his new 105 amp alternator thru the breaker it will pop his first time out.
Even with a 105 amp rating, the Delco 10si is going to cut back quickly..... but during any short duration heavy output, I'll agree if the alternator output exceeds the breaker's trip value!

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Thanks for all the responses. I am going to hook it up and see what happens and hope the breaker doesn't pop. I couldn't find a lower amp one that looked to be a replacement measurement wise but I'm sure I could have if I kept looking. What size wire should I use if the original is too small? What would happen if its too small?