Voltage Drop at Battery

I have a 1973 Correct Craft Skier. I purchased it knowing of a few mechanical issues.

One was a bad alternator.

I installed a new alternator and I know that it works. I am getting 14.5 volts at the alternator. Problem is that I am getting 13 v at the battery and 13 v at the starter (back of boat). As a result, the battery is not charging.

The alternator has an orange charge wire, that seems to run from the alternator, via a harness to the back of the boat. Then it runs to the dash, through an Amp Meter, and then back to the starter (as a red wire). I have been very perplexed as to why this is happening.

In troubleshooting I took a 10 or 8 Gauge wire from the alternator to the starter and the battery started to charge. This is not a solution, just proof that it can charge and that the alternator is not the problem.

The contacts on the charging wire, battery contacts and starter contacts are all clean and shiny.

Any ideas on what to do next in order to identify the problem to root cause?

Here's an early wiring diagram that should be pretty representative of what you have, complete with ammeter. Maybe it will help you, maybe it won't

I'll disagree with Pete and say you should be getting 14 or so at the battery like you're thinking.

It's a long and winding road from the alternator through the 8 pin connector,through the ammeter, through the key, back through the 8 pin connector and then to the connection on the solenoid that the battery also connects to.

I'd look at that 8 pin connector on the back of the engine assuming you have one and make sure those connections are all clean.

Lots of connections to check clean and tight

So firstoff I am not a boat mechanic - but I am an automotive mechanic. So that said some here may / should correct anything I mention that is considered a safety hazard in this environment. Also I understand the perspective of wanting to keep everything original if that's your cup of tea.

Check over the two poles of the ammeter and see if that's your trouble spot.

I've owned several 70s vehicles and over time the ammeters become a big source of voltage drop. On most that I own (drivers - not collectors) I bypass the ammeter by cutting off the rings - soldering inside an uninsulated butt connector - and shrink wrapping with marine sealant inside. Maybe the Correct Craft ammeters used are a better quality unit than older cars but this has benefited me many times on the road.

If that's not it then it's time to get a schematic and trace the path of the charge wire looking for your trouble spot. Depending on the electrical design (obviously I am not familiar with the design and any critical nautical features) I don't see it as inappropriate to run a nice heavy cable with an appropriate fusible link or fuse from the alt output to the battery. I like this particular mod because it's simple and takes the load off the original wiring without disconnecting anything - just makes the charge light (if equipped) and ammeter void. Lots of old Dodges I've worked on have overheated and at times melted charge circuit wires around ammeters and bulkheads.

Are there any bulkhead type fittings on boats like vehicle firewall connections?

**Edit: looks like some of this addressed above while I hunt and pecked away!

Went out and fired up the boat and got 14.2 volts at the battery with one of them VOM thingies through basically the same wiring setup as the diagram running at about 2000 rpm's.

The ammeter in this particular boat was bypassed years ago.

I just hooked the "goes in" wire to the "goes out" wire

I should add in also 14.9 volts at the alternator output

KENO wrote: I plugged and chugged some numbers and my real life voltage drop is only a little more than the calculated numbers. I probably went a little long on the wire length since I didn't measure it.

KENO wrote: Went out and fired up the boat and got 14.2 volts at the battery with one of them VOM thingies through basically the same wiring setup as the diagram running at about 2000 rpm's.

Ken,
I too "plugged and chugged" numbers when Mark first posted his problem with the voltage drop and used a worst case scenario. Keep in mind he did say he cleaned up his wiring but didn't mention the harness plug(s). Good point BTW! First you must use the total wire distance with DC and not half like the calculator states. That's for AC. I used 25 feet. Next I plugged in 10 gauge wire which is typical with an ammeter set up. Then for a load I figured a battery in need of a charge so I used 35 amps which would be the approximate output of the alternator for at least several minutes when the engine is started. That come out to a 1.75 voltage drop. I also asked Mark what type of battery he has since that too can make a difference.

BTW, if I went and checked my voltage drop per your recommendation, I'm sure I'd get the same results as yours since the battery is fully charged and new. I wish Mark would respond and fill in some of the blanks we both asked about.

I don't see any problem with the voltage readings you have now, but your 8 gauge wire to the solenoid would work and give more voltage like you saw.

The red from the ammeter isn't needed because it goes to the BAT terminal on the switch and there is a red 10 gauge wire already there from the solenoid.serving the same purpose of supplying 12 volts to the key switch

See the diagram earlier in the thread

If you're ditching the ammeter you could wire a voltage meter to the same orange wire that now feeds the ammeter.

Might be a confusing explanation from me , but you don't need it.

You can unhook it to verify that the boat still starts and runs, you'll just not have a working ammeter