Reversed battery connections on 85 Johnson 50HP Outboard

madmax

Hello,

I was working on my 16 ft. C-Dory in the evening, the lighting I had wasn't great, and I managed to hook the positive voltage lines to my engine to the negative terminal and the negative voltage lines of my engine to the positive terminal. Needless to say, I saw the spark on the battery terminal as the short happened, heard a pop under the engine cover on the 1985 50HP 2_Stroke Johnson, and smelled some smoke waft out from under the engine cover. I didn't see exactly what component in the engine failed at the time. I later checked all fuses in the engine, none were blown. I noticed that the bottom of the fuel solenoid (http://www.go2marine.com/product.do?no=153667F) looks like it has small bubbles in the plastic (burnt?), so maybe this is the part that failed (or maybe the bubbles were in there at time of manufacture).
When I try to start the engine now, it cranks, but won't start.

If anyone else has any guesses as to what part(s) may have gone bad, I'd really appreciate it.

Thank you,

-Max
max@tealeaf.com

T.R. Bauer · Posted: Sun Apr 27, 2008 1:53 am Post subject:

I am sorry to say, every single component that has a diode may have just died. This include the charging system, and any other computer component on the outboard. I hope I am wrong and it all works out ok for you.

Larry H · Posted: Sun Apr 27, 2008 2:44 am Post subject:

Max,

You can test the fuel solenoid by turning the key 'on' and then pushing in on the key. If the solenoid clicks, its ok. It is unlikely that just hooking up the battery backwards would damage the solenoid as it was not activated unless the key was pushed in.

The other parts of the electrical system may have a problem. The powerpack which supplies the ignition could be damaged.

Did you check the 20amp fuse in the wiring harness at the top of the powerhead?

T.R. Bauer · Posted: Sun Apr 27, 2008 12:53 pm Post subject:

Larry,

And even then, I do not see any reason by design that a fuel solenoid would fail even it were hooked up backwards. I remember when I worked on RVs long ago, an owner did hook up his battery backwards and this killed a variety of components: the converter, the invertor, the alternator, the ECM for the fuel injected engine, the ignitor for the distributor, and the alternator. What was really sad about it is that he bought the battery from us and I offered to put it in, but he said he was in a hurry and would do himself later.

No one ever does it on purpose, it just one of the little (but really BIG) things that you just can't do and get away with. I always check, recheck, and then check again, every time I do anything with a battery as any mistake can be so costly, and so instantaneous. Once again, I do hope that Max got lucky and it isn't anything serious.

madmax

T.R. & Larry,
Thank you for your replies, I appreciate it.

I did check all of the fuses, none had blown.
I just ordered a new rectifier online, should have that in a few days to try.
Thanks again for your advice that the fuel solenoid probably didn't fail.

I did some googling last night on this topic and came up with about (5) discussions (on various forums) of people who had unfortunately done the same thing (reversed battery cables on an outboard) and the consensus was that the rectifier was the most probable component to fail. If that doesn't do it, I'll try a new powerpack next.

I'll send a followup post when I eventually resolve this.

Thanks again,

-Max

cbgale · Posted: Sun Apr 27, 2008 6:42 pm Post subject:

I had a rectifier go, the engine still ran, the battery did not charge.

Larry H · Posted: Sun Apr 27, 2008 7:29 pm Post subject:

Max,

Before buying a powerpack, be sure to cover all the other things that could prevent the motor from starting.

Is the safety lanyard clip in place? Is the motor getting gas? Is the fuel hose hooked up properly?

A spark check can be made by removing the plugs, reinserting the plugs into the plug wires, placing the plug's metal housings against the powerhead bolts and cranking the motor. You should see a spark at the plug gap. Do not crank the motor with the spark plug wires disconnected. The ignition system produces around 80,000 volts and can damage it's self (or you!! )if the plugs are not connected.

I rethought wat I said earlier about damage to the powerpack and it might not be true. This motor should not require 12volts to produce spark. The powerpack is a capacitor discharge unit and is charged by separate coils under the flywheel that do not depend on the 12volts.

I have a 1985 Johnson/Evinrude shop manual and I will see if I can find it, and post the wiring diagram.

Larry H
Retired Johnson/Evinrude mechanic

madmax · Posted: Sun Apr 27, 2008 8:55 pm Post subject:

Larry,

Yes, I did check the below things yesterday, thank you for mentioning these ideas also:

> Is the safety lanyard clip in place? Is the motor getting gas? Is the fuel hose hooked up properly?

When the new rectifier comes in, I'll install it, and if it doesn't help things, I'll try the spark test you describe.

Thank you again for all of the advise.

-Max

Larry H · Posted: Sun Apr 27, 2008 9:51 pm Post subject:

Max,

I found and scanned the wiring diagram. Shown below in two parts. If you save them to your pictures file on your computer, they can be enlarged or printed.

They are in my album Here

As you can see, there is NO connection between the 12volt system and the powerpack ignition system. About the only thing which would be damaged by a reverse battery hookup is the rectifier. If the starter works, the motor should start.

Good luck,

Larry H

madmax

Larry,

Thank you so much for posting these wiring diagrams.
I'm printing them now.
I'll post a followup response once my new rectifier arrives and I've installed it.

-Max

madmax · Posted: Mon May 19, 2008 3:35 am Post subject:

Update:
Sorry for my late update on this. Here's the latest. I replaced the rectifier on the motor, it still cranked, but unfortunatly would not turn over. Before checking for the existance of spark being formed at the spark-plug when cranking, I noticed that the other electrical items on the boat were not working (bilge, cabin light, etc). Stepping on and off the boat (on a trailer), wondering what the heck was going on, all of a sudden these items started working again. I suspect a loose connection somewhere. After thinking about this some more and getting some pricing on a used/replacement engine, I decided to bite the bullet and order a new 50 HP Honda 4-stroke outboard. I'm probably going to have the wiring replaced at the same time and just start from scratch here to get some reliability and piece of mind. Thank you to all the replies on this, especially Larry and T.R. This is a great forum and it's good to know that there is a forum for C-Dory owners to assist each other.
-Max

Chivita · Posted: Mon May 19, 2008 11:28 am Post subject:

Max,

I killed a friend's old Datsun truck by doing the same thing. He had replaced both battery cables with red welding cables and I didn't trace the negative to ground, just connected the new battery as I thought it should go.

Sorry about the motor! Glad the battery didn't blow it's top on you!! You are not by any means the only person that has made this mistake. On a positive note, I bet this will never again happen to you!