Negative Polarity. Help

[Dunham78]

This dumbass(myself) hooked battery up backwards. Cranked motor a few times before realizing the bendix not engaging with flywheel. Now that I figured that out I have zero fire . Replaced inline 20 amp fuse that did not look blown. All wires appear to be in good shape and not burnt. Any help would be appreciated. 1975 Johnson 50hp. Thanks

 

[racerone]

Did you have spark before this mistake , yes or not sure ?

 

[Dunham78]

Yes, last fall I had zero issues.

 

[oldboat1]

Think I would test the fuse for continuity -- make sure it's functional. The rectifier was likely blown in a nanosecond when polarity was reversed, so would expect to replace that for battery charging system. I don't think a blown rectifier would give you a no spark condition on that CDI system (but might be wrong).

Go back to basics and fully charge the battery, maybe get it load tested. Shine the electrical connections with sandpaper, and make sure they are tight, then see if the motor will crank. If it cranks, test for spark (needs pretty high cranking speed to fire).

 

[boobie]

You may have blown the power pack.

 

[F_R]

Power packs are not connected to the battery. Unless you blew it while dinking around with improper trouble shooting.

 

[Dunham78]

It appears that I have very low power at power back. I can see a spark when I touch it with test light, but not enough to glow. And just on right side of pack.

 

[Faztbullet]

The fuse has nothing to do with spark..if starter works fuse is good. Rectifier likely tanked and agree with Boobie as sent 12v back thru kill wire and killed pack. And you cannot test this ignition with a test light ..despite what ya see on U-tube

 

[racerone]

Hopefully you are not looking for 12 volts from the battery to be at the powerpack.----And 12 volts from the battery is not used to make the spark on this motor.

 

[F_R]

As racer said, there should NOT be any battery voltage at the power pack. And if you do apply 12V to it, through improper testing or otherwise, you will blow it. Merely connecting the battery backwards will not blow it because the power pack is not connected to the battery. Same reason a bird is not electrocuted by sitting on the power line.

 

[Dunham78]

I found a rectifier of a 70 horse Johnson. Will it work on 50hp?

 

[oldboat1]

0583408 -- same oem pn for a 50 or 70 for '75. It's under $40.

 

[Crosbyman]

if you are handy with electronics that 3 wire rectifier looks like a regular full wave diode rectifier (2xAC IN) (1x +12 out) and body grounded

there are lots of full wave rectifiers you can test with before blowing an expensive OEM part

https://www.amazon.com/KBPC5010-Hig...ds=full+wave+rectifier&qid=1585085194&sr=8-12

2 pins with AC 1 pin for +12 and pi#4 grounded to engine frame

bolting these little square ones to the engine will provide heat sink or mount one ona small aluminum plate
(insulate all connections with heat shrink )

 

[F_R]

Agree, that bridge rectifier is just as good as the oem---probably better. And a heck of a lot cheaper at only a buck and a half each.

 

[Dunham78]

So I changed the rectifier and power pack from another motor and still no fire. What’s next?

 

[Vic.S]

So I changed the rectifier and power pack from another motor and still no fire. What’s next?

Go to the CDI Electronics Troubleshooting Guide I would think

 

[F_R]

Post #7 says you are seeing a spark when you touch it with a test light. Ask yourself Why? You have been told repeatedly there should be no battery power applied to the pack. How many more power packs will be destroyed before you believe? Never mind, I'm out.

 

[Dunham78]

Instead of being a ****. Why don’t you help me understand?

 

[racerone]

We are just trying to help you for a wee thank you that does not appear to be coming.----If all else fails read the instructions or visit the shop and pay the man.----I am bailing out too.

 

[F_R]

Hi again, this is ****. FYI, I have 24 years’ experience as a full time outboard mechanic, starting when I was only 16 years old. During that time, our shop was dealer for Martin, Gale, Clinton, and Evinrude motors. We also serviced Scott-Atwater, West Bend/Chrysler, Elgin, Wizard, Mercury, Homelite, and a host of others. Some people would drive half way across the state to get me to work on their motor. I also graduated from Radio/TV repair school, so have a fair knowledge of electricity. I got paid for my work. Now I’m giving my knowledge away free, not even asking for thanks. But a bit of respect wouldn’t hurt. And still, somebody calls me a ****.

Remember the bird on the wire. Both feet are on the wire, but he is not harmed. But if he were able to reach out and touch another wire, there would be a pile of feathers on the ground and bye-bye birdie. Remember, sitting on one wire does not a connection make.

I am posting a wiring diagram for your motor. Go ahead and study it, and find any place that the power pack connects to both sides of the battery. Take all day if you want. You won’t find such a connection. Yes, it is grounded to the negative post, but remember the bird, sitting on one side does not a connection make.
This means that if you are getting battery voltage to the power pack, there is a defect somewhere. That is why I suggested asking yourself “Why”.

Signed, ****.