25HP Evinrude won't charge my battery

[arks]

I have a mid-80's 'rude on a 14' side console Jon boat. It has electric start and runs nicely but the motor doesn't charge the battery. Ever since I bought it I've had to charge the battery before using the boat.
I assume all the 25's had a charging system but how do I know for sure? What part(s) would cause the motor to not charge the battery?

 

[tashasdaddy]

Re: 25HP Evinrude won't charge my battery

rectifier, if cables were ever placed on the wrong batt post, it is blown.

 

[arks]

Re: 25HP Evinrude won't charge my battery

Thanks. How can I test the rectifier?
I've got a multimeter and battery load tester.

 

[F_R]

Re: 25HP Evinrude won't charge my battery

Disconnect all the rectifier wires. Connect your ohmmeter to one yellow wire and the red wire. Should show a high or low ohms reading. Now reverse your test leads to the same pair. Should show an opposite reading from before ie if it was high, now it should be low.

Now repeat the same sequence with each or the other yellow wires and red

Now repeat the sequence again with each of the yellow wires and ground (the case)

3>yellow/red
3>yellow/ground
That's 6 diodes you are testing, in two directions each.

It has to pass all 12 to be good.

 

[arks]

Re: 25HP Evinrude won't charge my battery

Sounds easy enough. Thanks for the info!

 

[Lakester]

Re: 25HP Evinrude won't charge my battery

t'sdaddy sez:

"rectifier, if cables were ever placed on the wrong batt post, it is blown."

my oem service manual says on first page of electrical section:

"if the positive + post is connected to ground, the rectifier diodes may be damaged"

then one page over... it says,

"if the positive + post is connected to ground, the rectifier diodes will be damaged"

so when the iboats advice was to be sure to lable your - ground cable with a This Is The Ground attached tag, that is exactly what i did.

big yellow tag. i hope i dont mix them up, now. lol

ymmv, but i doubt it!!

regards,

lakester

 

[DJ]

Re: 25HP Evinrude won't charge my battery

Are you sure it has a charging system? Not all 25 Electric starts have alternators.

 

[steelespike]

Re: 25HP Evinrude won't charge my battery

Disconnect all the rectifier wires. Connect your ohmmeter to one yellow wire and the red wire. Should show a high or low ohms reading. Now reverse your test leads to the same pair. Should show an opposite reading from before ie if it was high, now it should be low.

Now repeat the same sequence with each or the other yellow wires and red

Now repeat the sequence again with each of the yellow wires and ground (the case)

3>yellow/red
3>yellow/ground
That's 6 diodes you are testing, in two directions each.

It has to pass all 12 to be good.

I thought Bridge rectifiers had 4 diodes? Are there 6 in In the outboard
rectifier?The 2 rectifier circuits I looked up Showed 4 diodes.If this is correct it might be good to show to arks.Would take some of the mystery out of it.
I have replaced the rectifier in auto battery chargers with off the shelf
bridge rectifiers.It seems we could do as well in an outboard.

 

[Barnacle_Bill]

Re: 25HP Evinrude won't charge my battery

I thought Bridge rectifiers had 4 diodes? Are there 6 in In the outboard
rectifier?The 2 rectifier circuits I looked up Showed 4 diodes.If this is correct it might be good to show to arks.Would take some of the mystery out of it.
I have replaced the rectifier in auto battery chargers with off the shelf
bridge rectifiers.It seems we could do as well in an outboard.

You are correct, just 4 diodes.

 

[samo_ott]

Re: 25HP Evinrude won't charge my battery

I concur with DJ. Are you sure it has a charging circuit on it?

 

[F_R]

Re: 25HP Evinrude won't charge my battery

I thought Bridge rectifiers had 4 diodes? Are there 6 in In the outboard
rectifier?The 2 rectifier circuits I looked up Showed 4 diodes.If this is correct it might be good to show to arks.Would take some of the mystery out of it.
I have replaced the rectifier in auto battery chargers with off the shelf
bridge rectifiers.It seems we could do as well in an outboard.

Well sort of correct...sort of. Some have 4 and some have 6. I'm fairly sure the 25hp that I wrote the instructions for has 6.

If the rectifier has two yellow leads, it has 4 diodes.
If the rectifier has three yellow leads, it has 6 diodes.

Alternators with 12 poles/6 pulses per revolution have the two yellow leads rectifier with 4 diodes.

Alternators with 10 poles/5 pulses per revolution have the three yellow leads rectifier with 6 diodes.

Anybody getting confused yet?