Difference in engine voltage while running
 

Going to dig into this.
On my 292 Formula, there is an almost 2v difference between port and starboard engines while running. Looked for obvious load differences(something on) and did not find anything. Batteries are new...and after a trip yesterday, I quickly measured the voltage on the two batteries with the boat on the trailer..13.0 and 12.5v.
Gonna start with looking at all connections I can find, but wanted to get some advice/ideas to help find the issue. The boat is a 2014, with only about 20 hours on it, so my hope is the hardware is good...just need to fine the source of the problem. Of course I could bring it to get it repaired under warranty, but hate the idea of dropping it off at a shop.....and I can learn some more about the boat.

Thanks.

it sounds like you might have an alternator problem or a battery issue.i would do a load test on the battery,s first,if they check out good i would check alternator output.

A charged battery should have a voltage of at least 12.8v.

verify that the purple wire is getting a good switched on 12v.

Had this come up with my 6.2s...the wire to the alternator had some corrosion on it. I probably could have cleaned it but I decided to put a fresh connection on it and it fixed it immediately.

Which wire? Thanks for the advice...hope it's a simple fix

Past years - Merc had a service bulletin about the routing of the alt wire and wanted it changed, most of the time the connector ended up bad inwhich had to be changed. back thenI think I redid at least 75 of these in a 2 year span including the bad connector. 2014 engines did not have this problem compared to the past. With that said it could be loose or a form of corrosion at the alt side.

Also for your app as Mike said (battery issue) weak cell in the battery - a fully changed battery is 12.7 to 12.8. Also there is specific gravity testing for wet cell batteries.

Also ALL the current marine engine manu's recommend a cranking battery for the engine only not a deep cycle and NO WING NUTS for the terminal connections. We have not installed wingnuts in years for connections at the battery especially for EFI / MPI engines.

I would load test the battery first and check all connections. Next is to scan the engines and read battery voltage that way to see what voltage output readings

Lastly what engines and engine serial numbers - sometimes it is best to at least call an OEM dealer ( have your engine serial numbers to report to them ) because service bulletins and recalls along with federal recalls are issue per engines and engine serial number groups that possible your engine falls under that needs to be fixed ASAP.

Thats great you want to fix it yourself but alot of times with new engines still under warranty or just coming out of warranty not really the best idea. Just saying as this could be a good way to void your warranty if it is still active.

That black wire on the back of the alternator. But like BUP said, check all connections. All it takes is one a little loose or corroded. It could also be the positive.

Well I did type this in my post but for some reason after I edited some missed spelled words it is gone.

Anyways the jist of it again.

The number one area for loose connections and or corroded connections is at the starter (12 V connection). Even with new boats very common problem.

check battery connections, back side engine ground connections in which is the second worst problem area for either loose and or corrosion along with the starter connections and of course at the alternator connections,

Take a hard look first in load testing the batteries for any problems there and how accurate are the Volt gauges at the dash ? Did
you use a quality volt meter for testing at the batteries when the engines were running at 1500 to 1800 rpms and at idle to read voltage output ?

Well, I think I have it figured out. Had both engines on the hose in my driveway, and was second guessing myself about what I saw yesterday....a difference in voltage from side to side.

The starboard engine battery was 12.98 v at rest. After starting, it jumped to 14.65 at the battery and 13.8 at the gauge on the helm. I was puzzled...but thought I had the engines switched in my mind.
Hooked the hose to the port engine and with engine off, batt was at 12.55v, and after starting, it went to 14.46 at the battery, and 13.8 on the gauge at the helm. Now I was really confused. Put hose back on starboard, and low and behold, I did have a voltage drop.....when the Corsa exhaust is engaged. All 4 solenoid are tied to the starboard power and switch....as you would expect I guess.
After unhooking all of the solenoids and looking for one that was misbehaving, I found that they all will drop the voltage from the gauge on the helm, you start at 13.8, manually plug one in, drops to 13.5, then 13.1, than 12.9, then 12.8. Reverse the whole process(unplug all, and start from the other side), and you get identical v drops. Plug any one in...and you get a drop from 13.8 to 13.5. So......all of them are the same.

What is weird, is that the battery voltage through this whole thing is 14.4v....so there is no problem with draining the battery. It must be that gauge uses an upstream source, after the accessories. Probably great for battery health, but not good for things that like 14v....like amps etc.

In any case, I am no longer worried about it too much, unless someone out there reads this and has a concern.

Thanks for the ideas...that is what is great about this site.

glad to see you figured it out.electrical issues can be a real biich to find sometimes.

Four solenoids can yank your voltage down that much? I would consider there is still an issue - the alt should be able to maintain voltage with that load. Otherwise it is badly undersized, which I consider unlikely from the factory. Check all connections for voltage drop while operating to find the culprit.

Those solenoids draw a bunch of current when engaged

Wow good find! That would have been way down my list of things to check. Glad you got it sorted out.

I read it different, I believe He said the actual battery volt stays same, but gauges go down in volts.

I think this is pretty normal (but not really acceptable) of the voltage drop many boats see up at the helm because of thin gauge wire(s) bringing the battery power up there.
edit in: too many power robbing things wired up at dash power source for the battery + wires coming up to the helm.

OK, that makes more sense - should have read closer, he DID say batt voltage held. I think I'd wire the solenoids through a relay to avoid that, or run new power lines to the helm like lots of us have-

This is right...I am looking into what to do to...if anything. There are no other accessories powered by this battery, so it is only the engine, trim pump, and the exhaust. All other stuff comes from the other engine, which has a bigger battery, and thus protects the port battery for starting.

Hi all, I am going to resurrect this thread.

In short recap of what is going on.

1) Alternators and batteries are both working well. Batteries at 12.3-12.6v without engines running. 14.1-14.6v when engines running. Conclusion....batteries and alternators are fine. This is verification by using a good handheld multimeter

2) When a large load(specifically the Captain Call switchable exhaust) on, the voltage reading on the helm, AND Garmin(via NMEA2000) shows that the Port voltage drops to around 12v. When the CC is off, the voltage is better...maybe 13v. Conclusion. For some reason, the NMEA AND voltage gauge on helm are NOT seeing the same voltage as the battery(which is at 14v when engines are running).

As stated earlier, I am not worried about the health of the battery and charging system...but.....why would the NMEA and the helm gauge show a low voltage? It cannot be the wiring to the helm because the NMEA does not use the same wiring(I assume).

I am looking for advice from any and all regarding how the NMEA and normal gauge is sensing voltage. Can someone let me know where the NMEA gets it's voltage? Then where the normal point of voltage sense for the helm would be? Trying to isolate why alternator and battery are fine...but the gauge for the port engine is showing low voltage.

Normally, I would not worry about the helm voltage...but as the NMEA voltage is low too....I have to believe that the engine is running off of the 12v(when Captain Call is engaged) This cannot be a good thing for the ECU and performance in general. There must be a bad connection somewhere...I am just looking for help in where to start looking.

Any help would be appreciated..

Thanks!!!

You could also run the main hot for 2 solenoids to the other batt, instead of putting all 4 on 1. And are you sure the NMEA isn't getting it's power at the helm where volts read lower?

I assumer that the voltage does not come from the helm voltage source as the Garmin reports voltage for both engines. My assumption is that it comes via the NMEA network...but not sure.

But I doubt there is a seperate hot run all the way back to the engines. They would take power from under the dash, probably right at the volt meters.

The Garmin uses the NMEA network, which taps into a bus that then connects to each engine. I am pretty sure it is a digital signal that comes from the ECU. Just not sure where the ECU gets the voltage signal. There has to be a loose, or sketchy connection somewhere.

Without knowing the particulars on the Engine Models and the Gauge set
A NMEA network will have 1 Power Source typically switched. This power Source is used for low draw devices connected to the network.
Values broadcast on a NMEA network are assigned PGN's and fields within the PGN's. NMEA Standard assign these to different manufactures.
Engine Parameters are generated by the sensors on the Engine and transmitted with unique PNG codes.
Simplest reference I found: http://continuouswave.com/whaler/reference/PGN.html

Other Sensors on the network can also broadcast voltages.


The Garmin can tell you what the PGN is for each value displayed. If you can obtain the PGN you will know what component the sensor belongs to.
Analog Voltage Gauges on the Dash are typically sensing the Ignition Voltage at the switch

I chased a similar problem on my Baja last year. Followed the wiring upstream from the batteries and found that my fuse box was where the voltage drop occurred. For me it was a simple fix, just required the cleaning of the contacts - Positive in, and feed to the gauges. Now my battery gauge reads as it should.