A new troubleshooting topic...so I don't threadjack

[bduffel]

Posed this in another troubleshooting thread but don't want to hijack his thread.


I've got a jon boat with a starting battery hooked to an electric start, power tilt/trim Merc 40 h.p. The starting battery (newish) loses voltage fairly rapidly when pos and neg cables are connected. I've removed every source of potential drain from this battery. It did it before I started running a rear sonar off it. I've since removed the sonar. It's like something in the starting/engine wiring is sucking up the volts. I tried the circuit tester light between the neg post and cable but got no light indication. Battery holds its charge with the neg cable disconnected but with it connected the batt. has dropped from 12.8 volts to 12.1 in the last five days. Down to 11.89 in seven days. With the cables disconnected it holds 12.8.

Now to update- I retested it and get a very dim indication on the circuit tester of some draw. Checked between the terminal and disconnected negative cable and it's drawing 228 milliamps. Checked between the terminal and hull and it's drawing 207 milliamps. Did a continuity test between the negative cable and hull and got a solid tone so something's grounded to the hull.

Am I wrong in assuming nothing should be grounded to the hull? The easy answer is obviously to disconnect the negative terminal to prevent the battery going down between lake trips but the whole thing's a little disconcerting.

Thanks

 

[Captain Ahab]

Nothing should be grounded to the hull - you gots a leaking something somewhere

Good luck - check all your connections 1st

 

[krawler]

Nothing should be grounded to the hull - you gots a leaking something somewhere

That is not completely right. You shouldn't use the hull to ground any accessories too, but the hull should be bonded to the negative side of the battery either through a separate ground wire or the main motor itself. Your on the right path, just keep disconnecting things until the reading is zero.

 

[theyyounggun]

Your electrical should be grounded to the negative terminal on your battery.

 

[rusty.hook]

Never heard of grounding the neg side to the hull, never have and never will. Been working on alum. boats since 1966 and never a ground yet. The negative side on the battery is your ground.
Check your charging system, on some motors it might be the resister

 

[rusty.hook]

Yall say ground from neg on battery to the hull, so how do yall ground your battery on a fiberglass boat?? YOU DON'T

 

[user 7806]

Your on the right track disconnecting things until you find the leak/short. By chance do you have a radio with the clock and memory for channels and all that? Some of them will draw a battery down, I know the one in my truck will so I keep a battery tender on it, doesn't get driven a whole lot.

Each item should have it's own ground wire and the best thing is to hook it to a bus that is grounded, my fuse panel has a bus bar in it. The motor itself is grounded and it is clamped to the boat hull so the hull will pickup the ground from that but the hull should never be used for a ground like the frame/body of a car.

Personally I disconnect by battery when the boat is not in use & I hook my battery charger/maintainer to the battery. Most people I know with boats disconnect the battery when not in use.

 

[huntinfool]

You should never ground the battery to the hull. That will start the electrolysis process and eventually eat up the aluminium. I think the problem is in the charging system and could very well be a bad resistor as suggested above. But you could just put a Perko on/off switch between the battery and motor and use that, instead of having to disconnect each time. This is what I did and it has served me well.

 

[Captain Ahab]

Just get a disconnect switch - like this:

 

[rusty.hook]

It was a resistor on my 1998, 60hp Johnson, changed and problem solved.

 

[Frogman Ladue]

You should never ground the battery to the hull. That will start the electrolysis process and eventually eat up the aluminium. I think the problem is in the charging system and could very well be a bad resistor as suggested above. But you could just put a Perko on/off switch between the battery and motor and use that, instead of having to disconnect each time. This is what I did and it has served me well.

Agreed. Grounding the hull creates an "earth ground"...you don't want this in a DC, battery powered system. This does drain the batteries.

Agreed again...you may have an issue in the charging system causing the draw....also, are you storing the engine with all the switches in the off position? Leaving a switch on may keep power to the primary side of the coil, thus creating a draw.

 

[JMichael]

Well I don't know about the engines that you guys are using but all the electric start motors that I've had experience with, had the ground cable from the battery bolted/grounded at the engine crankcase. This grounds the engine and starter which in turn grounds the boat hull as soon as you tighten the c clamp of the motor to the boat. So what steps are you guys taking to prevent your hull from being grounded? BTW, of the ones I've seen, none have had any sort of electrolysis issues. I certainly agree that you shouldn't use the hull as your ground source when wiring any accessory up in your boat, but I don't see any problem with the hull being grounded.

 

[rusty.hook]

So, how is a fiberglass boat grounded in your opinion?
In a battery closed system the battery negative is the ground.

 

[JMichael]

Why would we be considering anything to do with fiberglass boats on a site called "Tinboats.net" unless someone specifically said they were working on a glass hull and hoped to find some answers about it?

 

[rusty.hook]

So your saying a person can't have a fiberglass boat and an aluminum boat?. I bet there a whole lot of people on here that have both.
And why are you hijacking this thread?
See pics of my "Tin" below, how about yours?

 

[JMichael]

So your saying a person can't have a fiberglass boat and an aluminum boat?. I bet there a whole lot of people on here that have both.
And why are you hijacking this thread?
See pics of my "Tin" below, how about yours?

No, if you'll read what I typed, you'll see that I never stated or even implied that someone can't have both. What I did, was to imply that since the OP didn't specify it was a glass hull and that this was a forum about tinny's, that my comment was about tinny's. And since my comments up until the point that I responded to you, were about the OP's question and the original subject, I haven't hijacked anything. As for pics of my boat, I keep them linked in my sig so anyone can see them at any time.

Can we get back to the original topic about things being grounded to the hull, etc.

 

[rusty.hook]

Go for it. The 3 pics below is what my boat looked like when I bought it. Built and added all myself.