1971 Johnson 50hp - draining my battery

[Mitchsky]

Hi.
If I leave the battery hooked up while boating, the motor seems to drain the battery.
If I only use the battery for starting and then unhook it, then the battery seems unaffected.
I know that I need a new solenoid because we have to tap it to get the motor to start.
Can this solenoid cause the battery drain?
Is there a voltage regulator, is this the same thing as the rectifier, and is this what they do?

I would like to take the kids on the lake without any surprises this year!

Thanks.

 

[racerone]

Re: 1971 Johnson 50hp - draining my battery

You may need to do an ohm check on the battery charging coils in the stator.----Then test the rectifier.------------It is not a good idea to run that motor with batery cables laying loose and not connected to the battery.

 

[Bosunsmate]

Re: 1971 Johnson 50hp - draining my battery

Does the battery drain without motor running?
It shouldnt.
If it does, start disconnecting things untill you source what it is.
On my car i hook up the negative cable and then i disconnect the positive. I then put my red multimeter lead battery on +ve and the negative lead on to the negative cable from engine. In a car you get a few milliamps (i dont think its amps but might be) from running the clock etc but in an outboard switched off you should get 0

 

[boobie]

Re: 1971 Johnson 50hp - draining my battery

The rectifier is now probably blown from running it with the battery cable off. To check for battery drain. Take off the positive cable and hook up a volt meter with the positive lead of the meter going to the battery positive terminal. Take the negative lead of the meter and hook it to the positive battery cable. This puts the meter in series. Set the meter to 12 volts. If you get any reading at all you have a drain. If it shows a drain start disconnecting things until it goes away. You can do the same thing with an amp meter.

 

[Mitchsky]

Re: 1971 Johnson 50hp - draining my battery

Thanks a lot for your input guys. I try these ideas when I get it out of storage.

 

[F_R]

Re: 1971 Johnson 50hp - draining my battery

Hi.
If I leave the battery hooked up while boating, the motor seems to drain the battery.
If I only use the battery for starting and then unhook it, then the battery seems unaffected.
I know that I need a new solenoid because we have to tap it to get the motor to start.
Can this solenoid cause the battery drain?
Is there a voltage regulator, is this the same thing as the rectifier, and is this what they do?

I would like to take the kids on the lake without any surprises this year!

Thanks.

As already said the rectifier is probably blown from running with a disconnected battery cable. The solenoid shouldn't be causing a drain unless it is stuck and starter keeps running, but you should not be going out with defective parts. Replace it with the correct part (solenoids are NOT all alike).

I highly respect boobie and his experience, but I sort of question his voltmeter test. I'm thinking a quality voltmeter may show a voltage under such a condition. But I may be wrong on that. I'll have to ponder on that one.

 

[boobie]

Re: 1971 Johnson 50hp - draining my battery

F-R, I've always used my Stevens AT-101 for this test and it's never failed me. One of my Mentors in an auto-electric shop I worked in in the early 60's taught me that trick. As I said in the post, you can also use an amp meter. I've always liked the voltmeter better though, as it's more sensitive.

 

[F_R]

Re: 1971 Johnson 50hp - draining my battery

Ampmeter, yes. Milliamp meter, better. I gotta try that voltmeter though. Never have.

 

[Fed]

Re: 1971 Johnson 50hp - draining my battery

The rectifier is now probably blown from running it with the battery cable off. To check for battery drain. Take off the positive cable and hook up a volt meter with the positive lead of the meter going to the battery positive terminal. Take the negative lead of the meter and hook it to the positive battery cable. This puts the meter in series. Set the meter to 12 volts. If you get any reading at all you have a drain. If it shows a drain start disconnecting things until it goes away. You can do the same thing with an amp meter.

Maybe too sensitive Boobie, I went on a wild goose chase after using an analog voltmeter to check for leakage.
It all started when I noticed a tiny spark at the battery terminal when I was disconnecting for some other reason so I put the meter in series and got a 6 Volt reading.
The leakage turned out to be 'something in the motor' (probably rectifier or regulator) and a 2 way radio that apparently has a diode connected across the incoming supply wires to prevent connecting with wrong polarity.
In my mind the reading at 6 Volts put the external leakage resistance roughly equal to the internal resistance of the analog meter which is negligible for this exercise.

I guess what I'm saying is a reading on the meter may not mean there is a problem.

More than happy to be corrected on this because it's a little above my pay grade and life's too short to go through the google learning curve.

(Bruce58 where are you???)

 

[boobie]

Re: 1971 Johnson 50hp - draining my battery

Using the volt meter if you get a reading and disconnect everything until the meter zeros at least you'll know where the problem is. Maybe it needs fixing or maybe it doesn't.

 

[Fed]

Re: 1971 Johnson 50hp - draining my battery

Good point boobie.