Twin '05 VP 5.7Gi-EF - Low voltage on Starboard engine

[dhbrown35]

I have a 2005 Chris Craft with twin 5.7Gi-Ef's with approximately 300 hours. The starboard engine has been starting hard for a few months now. Around Thanksgiving I pulled the batteries and tested one at AutoZone. Sure enough it wasn't making full amperage. I replaced all 3 batteries and the boat fired right up.

Fast forward a couple of months later and I am having the issue again. I noticed the voltage for the port engine is always around 14 volts prior to starting, but the starboard is 10 volts. I tried every possible position of the battery switches and it doesn't move from 10. On Sunday I physically moved the batteries and got the same voltage of 10v, but it did start.

Once it's started the voltage does jump to 14. What could be causing the low voltage prior to start, and could this low voltage be part of my hard starting issues?

 

[BarryTurano]

Bad ground or something draining that battery. What is connected to that particular battery? When the motor is running are you getting 14 volts to the battery. Could be the alternator is getting weak.

 

[BarryTurano]

Just re-read your post. Forget the alternator part. I would look for a leaking ground on that battery.

 

[Maclin]

Swapping the batteries and monitoring the behavior for a period of time may help eliminate a "cranky" battery :noidea:

 

[dhbrown35]

Ok, any ideas of where to look for that leaking ground? The battery switch? Motor ground, I am not even sure where that would be, but I am guessing it's not uncommon to get some corrosion that could cause issues?

 

[alldodge]

voltage for the port engine is always around 14 volts prior to starting

starboard is 10 volts

Needs some clarification, First no battery should read 14V "PRIOR" to the motor starting.
How do you know its 14V, and is the shore power battery charger still connected and powered ON?

 

[Rick Russell]

I had an issue similar to this and I cleaned the ground connection on my alternator and it fixed the problem. The old one looked fine, but once I disconnected it you could see that the bolt was corroded and essentially acting like an insulator.

 

[Lou C]

The batt should read approx. 12.6V if its fully charged with the engine off, it might be slightly lower like 12.5 or 12.4 (that's about 80% charged), but not 14 for sure.

 

[Scott Danforth]

start at the batteries and clean every connection to the motor and back. take them apart, use 3M scotchbright pads and make everything shiny enough to eat off of. battery terminals, starter terminals, block connection, alternator connection, etc.

if you still have a problem, take your alternator in to an alternator/starter repair shop and have it tested.

also, use a volt-ohm meter and actually test the voltages. your $3 dash gauge could have gone belly up.

 

[KAR37922]

Lets look at what you are measuring. Are you measuring on the battery from the + to - terminals. If so, then make sure your shore power is off and the battery charger is not charging. Then measure again. Now connect shore power so the charger is charging, compare the measurements. I'm betting that your issue is that your shore power charger for that engine is not charging, thus seeing 14V and 10V. And that explains why once you bought new batteries all was good . . . . for a couple of month.

 

[KAR37922]

If its not charging, look for an inline fuse or a breaker.

 

[dhbrown35]

Ok, I have some to do’s when I get back in town and on the boat. Unfortunately that’s going to be Saturday or Sunday at the earliest.

Went out last night for dinner with the fam and it started within a few minutes. I bet swapping that battery made the difference on Sunday but it’s only a matter of time before that battery loses its ability to start the engine.

Great point on the voltage being 14 prior to starting. That can’t be right. I will test each battery directly with the multi-meter. I will also clean all connections including the alternator ground.

All that said I am suspecting a failing alternator. (and a suspicious voltage gauge on the port engine). Will a failing alternator damage a battery?

One last note, when attempting to start on shore power I was seeing the same readings on the dash gauges. I’ll test that with the multi-meter as well. Not sure what that tells me as it was my understanding that the shore power uses a separate charger while the engine are off and the alternator when the engines are running.

Thanks everyone for your expertise. I will post ASAP.

 

[alldodge]

Will a failing alternator damage a battery?

Yes

when attempting to start on shore power I was seeing the same readings on the dash gauges

If shore power is still one then your battery charger is still ON. The battery charger will show a possible 14V.
The 10V with shore power could be you need another battery charger. In any case need to get some more readings with a meter