Electrical issues with 1973 Johnson

[lpotvin]

My motor is 55hp Johnson. It contiuosly draws power from my battery. Technically I should be able to start this motor by pull starting it and keep it running with no battery at all, correct me if I am wrong! Where do I start looking for issues, starting with easiest. Thanks for you time.

 

[jtexas]

Re: Electrical issues with 1973 Johnson

Assuming your motor has electronic ignition ('73 50 hp does, but there's no 1973 55hp Johnson - some pre-72 models have battery CD ignitions) you could technically run the motor with no battery, but it would fry the rectifier, which is the component that converts AC power generated by the alternator into DC power that can be used to charge the battery and power the accessories.

There's a thread in the "Engine FAQ" section of iboats with the step-by-step rectifier test procedure - it's your number one suspect.

Why the motor is drawing current, not sure - how did you determine that? Any accessories running at the time (like maybe a tachometer)?

 

[lpotvin]

Re: Electrical issues with 1973 Johnson

I detemined the battery was using power by, when the battery was draining that the boat actually ran at a slower speed and continued going slower and slower till the battery was completely dead. I then would not be able to start the boat, putting a huge damper on the salmon season! I appreciate your help.

 

[jtexas]

Re: Electrical issues with 1973 Johnson

First you need to identify your motor, so you'll know what kind of ignition system you have. Johnson didn't make a 55HP motor in 1973. There should be a model number on the port side of the engine mounting bracket which can be used to cross-reference the year.

Then its just a matter of basic troubleshooting.

Here's a pretty good resource for step-by-step:
http://cdielectronics.com/portals/0/downloads/Troubleshooting Guide 2006.pdf