My 3-year electrical headache was solved today, and it was a simple fix! Wondering if this is common.

[DJ_Allatoona]

For several years, I haven't been able to crack the code to getting the more sensitive 12V stuff on my old project Starcraft to behave properly. Stereo head unit, amp, fishfinder, running lights. Most of the time, everything is great, but sometimes they switch off when I throttle up, sometimes I'll get voltage spikes higher than 16V, I've seen 18V on my Garmin, and it will power down with the message, "HIGH VOLTAGE". Sometimes my amp will power on, sometimes it won't. Doesn't seem to be a pattern and it makes me crazy.

I have run new wires, upgraded my fuse block, replaced the switchbox (it needed it), tested the stator (all good), chased all the grounds, replaced connections and terminal ends with heat-shrinks, I even added an aftermarket voltage regulator to my old outboard that wasn't made with one. No help. Everything points to a short somewhere but I could never track it down.

So today I had my battery tested AGAIN, and it's good. It has always tested strong, no bad cells, never suggested replacement, so I considered it good. Cranking is fine, tilt/trim works nice, I thought no battery issue. So I'm telling the guy at Pep Boys, and he had a hunch: -- he tests the battery again, this time on the threaded marine posts, instead of the auto/SAE posts. The test numbers come back garbage! 5 CCA on a 675 CCA battery. Next test: 1 CCA. Message "REPLACE BATTERY". I have always tested my battery on the auto-style posts because it's easier for the clamps, but I use the marine posts for my components. It never occurred to me to do it otherwise.

I got a $6 terminal adapter from Walmart, connected everything back, and like magic, everything works beautifully. For the first time in years, everything comes on and meters 12V or 12.5V as it should. Took a long test ride on the water and zero issues. I almost cried.

So, what does this mean? Is it common on a marine battery that the 3/8 threaded posts are bad, but the auto-style posts are good? Does it mean this battery is on its way out? I have never heard of this type of failure before.

 

[Bondo]

Ayuh,..... Dirty, rotten wiring connections are common,.....

Never seen such a problem with bad posts,....

 

[redneck joe]

Interesting.

 

[Lou C]

What were you using to secure the battery cables to the small threaded posts? Wingnuts? If so they can cause problems because they don’t stay tight. Use locknuts instead or a stainless nut with a lock washer. I bolted auto style but marine grade clamps to my cable ends and use the big posts.

 

[dingbat]

Post a picture of your connections

I have never seen a dual use battery where the marine terminal (threaded connection) is not cast into a common (lead) battery tap.

That being the case, current is transferred thru direct contact between the lug and the lead tap. The threaded connection does nothing but secure the (3/8”)lug to the tap.

If you connect your test clamp to the screw without full contact with the pad, you will get erratic readings because a 3/8” stainless screw does not have the cross section to carry the full current of the battery.

Cable lugs and taps (lead) need to be shiny and the lugs tightly secured with ny-loc nuts.
I apply a light coating of dielectric grease to both surfaces prior to assembly to help prevent the surfaces from oxidize over time

 

[DJ_Allatoona]

What were you using to secure the battery cables to the small threaded posts? Wingnuts? If so they can cause problems because they don’t stay tight. Use locknuts instead or a stainless nut with a lock washer. I bolted auto style but marine grade clamps to my cable ends and use the big posts.

Thanks, and yes, I was using stainless hex nuts on the posts. Still can't believe the battery was the culprit all this time. I spent so much time chasing ghosts and beating my head, when I could have just replaced the battery.

 

[redneck joe]

Well, think positive. You did a bunch of upgrades so now you have a better boat.

 

[DJ_Allatoona]

Well, think positive. You did a bunch of upgrades so now you have a better boat.

Yes, that’s an upside. On to the next project…!

 

[Chris1956]

It appears that your motor has a simple full wave rectifier which converts the AC charging current of the stator to DC for battery charging.

Inherent to this kind of charging system is the battery which acts a load on the charging system reducing the voltage to near battery voltage and acting as a sort of voltage regulator.

Often in these systems, a higher than battery voltage is seen in the charging system. This high voltage could be the source of your 3 years worth of problems. If the voltage issue persists, you may need to add a Zener diode or a voltage regulator to control the high voltage.