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reversed battery polarity

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Russ43

New member
I committed the ultimately sin and accidentally reversed the cables on one of my pair of batteries. When I tried to start, it fried the other battery. I was able to start the engine on the one good battery, but had insufficient power under load. I could only get up to about 3800 rpm which was not enough to get on plane. Back at the house, I replaced the bad battery, checked that the other battery was still able to hold a charge, replaced the ground wire connecting the two, and replaced a 30 amp inline fuse (it looked fine but I replace it anyway). The engine runs fine on the muffs, but on the water I have the same problem--maxing out at 3800 rpm and insufficient power to plane. Given that the current from the improperly connected battery seemed to go to the second battery, what else could I have damaged that would cause this problem (e.g., power pack, stator, etc.)? The engine had recently been serviced and was running fine, so I am assuming it is not a separate (e.g., fuel) problem. I have a 1988 Johnson 120 outboard. Thanks for any leads.
 
Hard to answer as I'm not sure what you did? Are you by any chance running a trolling motor with this other battery?
 
No trolling motor. Just a starting battery and a second deep cycle battery to run the console. They are connected by a common ground cable and a perko battery switch that was set to 'both' when I started the engine.
 
I'm still a little unsure what you did wrong? Just starting the engine on Both batteries would not be a problem, technically. (Depends on quality of battery switch?) if you crossed the battery cables (positive to neg. & vice vesa) then you would have had a dead short if the battery switch was on both?
The motor doesn't need a battery to run once the engine is started. It does need to charge the battery to keep from damaging the charging circuit/stator. The ignition system is on its own pretty much once the motor is running. I'm not sure the two are related. Maybe someone else will chip in here with other ideas. The variables as to what happened are endless. Sorry.
 
I crossed (pos. on neg. terminal and neg. on pos.) the battery cables for the starting battery--the one going to the engine. The second battery, which runs the console and is connected to the first via a common ground cable was hooked up to the correct terminals. Because the polarity was reversed on the starting battery, the engine did not start and when I turned the ignition it fried the second battery (the common ground was connected to the pos. terminal of the starting battery and the negative terminal of the second battery). I immediately hooked up everything (console and engine) to one battery and it started fine, but did not have sufficient power (max 3800 rpm, would not plane). When I later replaced the fried battery and re-connected everything correctly and in the original configuration--same thing--starts fine but no power under load. An earlier response suggested I had fried the rectifier/regulator assembly and potentially the power pack. So I will check these. Any other suggestions appreciated.
 
Well it's possible that the rectifier/regulator could be damaged, but it would be more likely if the motor had started & ran? The power pack should not be bothered (although a common mis conception). It does sound like the motor may be running on less than all four cylinders. Do you has a set of plastic pliers (like fuse puller pliers), not insulated pliers! Those will get you BIT every time. Start the motor (better in the water with a little load) & pull off one plug wire at a time. You should notice a drop in RPM each time you pull one off & put it back on. If you do it in the evening you can see it firing to the plug. That's the best place to start.

Dan in TN
 
Hi...i am a new user here. The motor doesn't need a battery to run once the engine is started. It does need to charge the battery to keep from damaging the charging circuit. The ignition system is on its own pretty much once the motor is running.
 
Russ... If you threw reverse polarity to the engine, you blew the rectifier portion of the water cooled voltage regulator, rectifier assembly. Now, whether that's affecting your top rpm, I really can't say.

Dan... Why are you yelling? :)
 
First off you never want to connect in parallel two dissimilar batteries. The tach is working but is it correct? It works off one leg of the ac circuit from the stator do you have a volt meter? You could have multiple issues start with the basics. Get a DVA adaptor for your volt meter and go to CDI marine electronics and start testing components. A bad regulator can cook the stator and battery and versa visa. A bad stator can cook your powerpack so take your time and be thorough. It can get alot expensiver if you dont make sure all components are working properly before you put it into service. A volt meter/s and a battery isolator will help protect from future expensive repairs. Keep the house circuit independent from the engine and guages.
 
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