Battery Problem

[harmony]

Need some help. I am getting my 26x ready to launch and was hooking up my batteries when I inadvertantly switched pos & neg on my small battery, quick spark at the terminals. I corrected this quickly and proceeded to connect my larger battery. There is an isolator switch so I can always have a battery with power if one becomes discharged. Problem is now I have no power to my engine from either battery,and no power to the power trim. I do have power to everything else in the boat. The engine is a 1997 Nissan 50 Hp. Are there any fuses some where along the way that may have blown?

Any ideas what may be going on?

Thanks
Doug

[richandlori]

I hate to even say this, but that could have shorted out the batteries and they could now just be heavy chunks of lead and acid. I would remove connections to the battery and check them individually to see if they have a dead short

Yikes.


Rich

[Catigale]

I doubt a quick connect would kill the batteries..

I think you are on the right track looking for a blown fuse..just follow the live 12VDC with a voltmeter and look for 12V until it drops...manual might help too.

[craiglaforce]

I looked at my Tohatsu shop manual today. THere is a 20 amp fuse. Not sure where though. I would look under the little black pastic electronics covers.

[billd]

Doug,

I did the same exact thing almost. Accidently hooked up pos red cable to neg post etc. Left it that way overnight and then ran lights while working inside. Lights winked out and next day noticed my mistake and switched to be correct. However, lights work, lift on motor switch works but pedestal is dead completely. With my lack of electrical skills I worked on it for a while and now its headed to the shop this week. I am guessing a blown ignition switch? Any ideas? Thanks.

Bill

[craiglaforce]

The shop manual showed the fuse between the ignition switch and the starter relay.
Maybe the fuse is in the remote control unit on the pedestal, especialy if this is where you see the power outage.
It wasn't clear where it was from the book.

[Catigale]

My guess is the fuse in an integral part of the starter circuit and would be under the engine cowl like on my MERC 50HP EFI BF. You should be able to trace the Big Fat wires to it pretty easily though.

[HERNDON]

I borrow some of my daughter's bright red fingernail polish and
paint both the terminal top and cable so there will be never be a
question. A 10 second fix. ( a mod for the mod page)

Also did this on the cars and jumper cables for both of the kids
and wife. Just in case... red to red is easier than positive to positive...
I also highlight the + on the battery for when I am charging it
in case of heavy solar flares and I become stupid. Good thing
we are near the bottom of the sunspot cycle.

Rob

[ALX357]

don't want to be alarmist, but it is possible to fry the alternator electronics on the motor, with continuous reverse-polarity applied voltage.

[billd]

Learned a valuable lesson. It cost $82 to learn about the 20amp fuse on the port side of my 50hp Merc. This was blown when the battery had reverse polarity on it for a short time. Everything else was good and now I know. My electrically inclined friends in town are having a good laugh. Thanks for the replys. I have watched this fourm for a couple years now but never logged on. Glad I did.

[Catigale]

Im still a bit intrigued that reverse polarity would blow a fuse. Is this fuse specifically in the circuit (like in a rectifier bridge) to protect against reverse polarity??

The DC resistance of most electrical loads on the boat don't change with polarity...of course diodes have polarity and can blow and ergo you can torch your alternator

Any EE have some knowledge they can share here??

[waternwaves]

having not looked at the wiring for that particular engine.....

my guess is the engine control computer is protected from reverse polarity. Most engine computers in this vintage....do not have intrinsic clamping surge protection. And the MCU computer is nothing more than millions of organized diodes......

[Divecoz]

MCU stands for ???

[Zoran]

There must be a fuse under the motor cover. On my 30HP almost every time I play with electrical system it will blow, motor will start only by hand and choke will work only manually too. I find about this fuse by looking schematic of the engine and there was nothing about it in the manual. But that was a start, once I found out that there must be a fuse under the cover I started searching and found it in black rubber cylinder on one of the red wires.

Zoran