House Battery vs. Starboard battery

The charging voltage was 14.3 on both at the dock when the engines were first started.
 
Good to know. What I still do not understand is why after being underway for a few hours one stays at about 14 volts while the other (which is the newly added battery) drops to 12.4 before the regulator rectifier kicks in and bumps it up to 14 volts.
 
JLR said:
Good to know. What I still do not understand is why after being underway for a few hours one stays at about 14 volts while the other (which is the newly added battery) drops to 12.4 before the regulator rectifier kicks in and bumps it up to 14 volts.
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The regulator/rectifier as you call it does not kick in. An ACR or similar device can have act like that.
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I am not sure where you are measuring the battery voltages when under speed but my first thought is that one battery is not charging. Your voltage with the motor running above idle ( 2000 or so revs) should be higher than 12.4 volts.
It seems that one battery is discharging. When you do these tests, what is the battery selector switch set to?

If each battery is connected to a single engine, each should charge independently of the other.
Either there is a wiring issue (bad or mis wired) or one engine is not charging.
Is the following correct:
You have two engines
You have one battery switch
You have only two batteries
One battery is the feed for the house loads
Is there an ACR somewhere? If there is, I don't understand why

One more question:
the battery that reads 12.4 volts; If you stop the engines and put the battery switch to OFF, does the battery still read 12.4 volts or is it higher?
 
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If you have a load tester, leave the battery cables connected to the new battery that reads low periodically and disconnect the cables at the other end. Connect your load tester on that end of the battery cables and apply the load there. That will test the battery cables also. You didn't say how old your boat is or if it has spent a lot of time in the salt. I personally have had battery cables corrode away from salt wicking in from the crimp. When I load tested the cables the ground cable actually caught the insulation on fire and fell in two. It had corroded away to where there was less than 1/4 of the cable left and no doubt that was deteriorated.....just a thought. Something strange is going on. Figure out if you have an ACR in the mix and make sure it is wired correctly or remove it from the system till you get your problem figured out.
 
As far as I know, I do not have an ACR. I have two battery switches not one. The starboard switch is set to battery 1 and the port is set to battery 2. As others have noted, battery 1 is the house battery. Not sure about the last question but at rest, with the switches in the above position, both batteries read about 12.9 volts.
 
JLR said:
As far as I know, I do not have an ACR. I have two battery switches not one. The starboard switch is set to battery 1 and the port is set to battery 2. As others have noted, battery 1 is the house battery. Not sure about the last question but at rest, with the switches in the above position, both batteries read about 12.9 volts.
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Battery number one is only the house battery if you have the starboard battery switch set to number one. If you have the starboard battery switch set to battery number two then battery number two is the house battery. The starboard battery switch powers, the house regardless of which battery is selected. That assumes your boat is wired in the standard Grady-White manner.
 
How about a completely different possibility. What if the contacts on the starboard battery switch have some corrosion. They may not be letting a full charge into the house battery. I'll try to exercise the switch a bit and see if that makes a difference. Could that be a possibility?
 
I would definitely check your battery switches and all contacts for that matter, for corrosion or not being tight enough. I swapped out both batteries on my boat in September/October of 2023, two years after buying my boat. I usually leave the boat out on a mooring buoy in front of our beach cabin all summer, and when bringing her in for the season, she wouldn't start. Replaced both batteries, brought the boat in and didn't have any other issues that season. Then the next spring, tilted up the motor, updated the GPS with updates and took her down to the boat ramp. Pulled her off the buoy and she wouldn't start, would just give a "click" noise and then nothing. Got the boat back on the trailer after tying up part of the dock for a bit, took her back to the cabin and went over all of my connections again. Put a wrench on one of the battery terminal nuts, gave it the slightest bit of tightening and that was all she needed. Not sure if the terminals just weren't making good enough of a connection with the connectors or what happened, but loose connections and corrosion can very much give you starting/charging issues. Just out of curiosity, the battery that you replaced that was only two years old, was it an AGM or wet cell battery? A two year old battery, unless it was a dud from the factory, had been drained down multiple times or some other issue... doesn't seem like it should have an issue with it, especially only being two years old.
 
It was a wet cell battery.
 
turn both switches to OFF
Set switch to 1 (switch 2 still off)
then test what works, trim (test both engines), crank ( just a small crank,
electronics (MFD horn, Take notes.
Now set switch 1 to 2 and redo tests.

Now do the same for switch 2, set switch 1 to off and switch 2 to 1
Test as above
finally set switch 2 to 2 and retest the above.

I am trying to figure out how the switches are wired.
 
Well, subject to a test run tomorrow, I am tempted to just replace the regulator on the starboard engine. I am hoping it might be the regulator not properly charging the house battery. I am also hoping I do not have a stator or other wiring problem. With that said, these are 2012 Yamaha F300 motors. Despite looking online at the parts manual, I am unsure what I need to take off to access the regulator. Can anyone advise on this. Some sites say I need to remove some silencer, others say the intake manifold, others saying I need to nothing at all.
 
not sure about your engines but my old ox66 was a nightmare. unit was bolted to the block and cooled by salt water flow. needless to say bolts were hard to get out and one sheared. had to drill it out and tap hole which miraculously worked. good luck. ps symptoms were similar to yours which is what necessitated replacement
 
To clarify one term:
If you have two batteries total, each is a starting battery. There is no house battery per se but rather one of the starting batteries is also the source for your House loads.
 
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Back to the original post, when you’re looking at your Garmin engine page (assuming it is configured correctly when installed) you’re looking at each engine alternator output to the associated battery switch, not a specific battery. Regardless of the battery that you have selected your starboard indication on your Garmin engine page will be reading your alternator output from that engine.When your engine is running, it should put out about 14 V. They are smart alternators so they may not put out that voltage until they have been running for several minutes. It is somewhat normal for the voltage to drop when you are running loads on it Such as your trim and tilt. You may or may not have a problem, but there is no such thing as a house battery. There is a house switch and it is a starboard one. If both your alternators are putting out 14 V, there’s nothing wrong with your alternators.
 
wspitler said:
Back to the original post, when you’re looking at your Garmin engine page (assuming it is configured correctly when installed) you’re looking at each engine alternator output to the associated battery switch, not a specific battery. Regardless of the battery that you have selected your starboard indication on your Garmin engine page will be reading your alternator output from that engine.When your engine is running, it should put out about 14 V. They are smart alternators so they may not put out that voltage until they have been running for several minutes. It is somewhat normal for the voltage to drop when you are running loads on it Such as your trim and tilt. You may or may not have a problem, but there is no such thing as a house battery. There is a house switch and it is a starboard one. If both your alternators are putting out 14 V, there’s nothing wrong with your alternators.
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Thank you. Very helpful. If the starboard engine puts out 14 volts at the dock that's good. Since you indicate it is a smart alternator, is it then normal for it to kick in again underway when the load on the starboard battery has dropped to about 12.5 volts? In other words, is a drop from 14 to 12.5 while underway and with loads before it goes back up normal?
 
I don't know for sure if that is the case. I would doubt it though. These motors produce charging current even at idle. I would expect voltages to be in the 13+v range

I am also not sure that 14 volts at the dock is the norm. The voltage should depend on the battery's state of charge. If you turn off all accessories (as much as you can at the dock) try measuring the voltages of both batteries with the battery switches set to one on 1 and the other on 2. I would expect the voltages to be the same and higher than 12.5. Do the tests again with the engines running. Again I would expect the voltages to be similar
Also do not use the same ground point for the two battery measurements. Use the negative terminal and positive terminal of the battery being measured.
 
Here is a brief update after speaking with the local Yamaha tech who services these engines. He said that the regulators do not usually go bad on these engines. So, a prophylactic changing of the starboard regulator appears not to be in order.

Next question. The Grady White plate on the inside of the battery switch compartment says that the "Normal" position is starboard switch to battery 1 and port switch to battery 2. Why is that any moe normal than starboard to battery 2 and port to battery 1?

I intend to flip the switches to the not normal position today and see if the draw on the starboard battery shifts to the port battery.
 
Your nomenclature is a bit confusing. Batteries are not port and starboard. They are number one and number two. Switches are port and starboard. I think understanding that issue or configuration may help you with your troubleshooting.
 
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