hooking up wrong wires on battery

[Mr. BrownTrout]

A friend has an electric start mercury 7.5hp, he made the power cables longer but forgot to mark the positive from the negative, well he hooked them up wrong and some smoke came from the back of the engine and he quickly unhooked the wires and then hooked them up the right way, he says the motor still turns over, but there is not gas in the engine because he had winterized the motor. Did he do any damage to the motor???

[Highmark]

If there was an diode in the loop. yes, If not maybe he only got things real hot. But If I were a betting man. I would bet on Yes.....

[baitsauce]

Yup. Fried the diodes. Shouldn't be to hard to fix though.

[Mr. BrownTrout]

Neither he nor I are mechanics, but if the diodes were fried would it still turn over??? I told him to go get some fuel and see if it will start. It also has a rope for pull starting.

[baitsauce]

Neither he nor I are mechanics, but if the diodes were fried would it still turn over??? I told him to go get some fuel and see if it will start. It also has a rope for pull starting.


It will start and run normally. You won't hurt it more than what it already is by running it. It just won't charge the battery. You can probably even crank it with the starter too.

A buddy jumped his truck off of mine when early during an elk season one year. Dummy me I didn't watch him. He hooked the jumper cables up (to my truck as it was running) backward and poof! Fried the diodes in the alternator. Long story short he got really tired of taking my battery out everytime we ran the generator for the camp (during the evenings) to charge my battery so I could start and drive my truck the next day. When I got home I changed out the diodes and I was back in business.

In the flywheel of your motor is a magneto that in a nutshell, provides the juice to run the spark plug. So unless you really need to charge your battery, you don't need the wires to the battery from your motor. In fact I even fished for a few years before I even bothered to hook up my charging system of my kicker motor.

Hope this helps, but PM me if you have any other questions........

[Mr. BrownTrout]

I called my friend up today and found out he had went and got gas for his trolling motor, the merc 7.5, and it fired right up. I told him what you guys told me and when he gets time he is going to investigate those diodes.
Thanks for all the info