1991 Jonson 70 Hp Charging Problems

[SRobideau]

As stated in the title I have a charging problem with my outboard. I realize that this has been addressed before but I seem to be having some difficulty.

To solve the problem I thought it was a simple as testing the rectifier and stator to see which was bad. It turned out that the stator tested bad. I replaced the stator and while i had the cover off I replaced the rectifier. After all the effort the volt meter reads 12.5-12.75 from the charging system. This should be over 13 volts?? Is there something else that I am supposed to check? Or could the stator that i bought be bad? I am a little lost here. Also, after I replaced the components and measured the voltage there is some oscillation in the voltage. The oscillation is small, approximatly 1 volt. In other words I am still reading AC at the terminal leads. Is this normal? I though the rectifiers job is to filter out all the AC and leave just the DC to charge the battery? Anyway, any help or direction would be greatly appreciated.


Thanks,

Scott

 

[jtexas]

Re: 1991 Jonson 70 Hp Charging Problems

I'm confused...if the rectifier output is 1 volt AC, where are you measuring 12.5 to 12.75 and is that AC or DC?

 

[SRobideau]

Re: 1991 Jonson 70 Hp Charging Problems

I am reading 12.5-12.75VDC at the battery leads, but there is a slight oscillation in the voltage signal. In other words its not a flat 12.5 volts. The signal will oscillate between 12.25VDc and 12.75 for example. It seems to me that the voltage should be a consistant voltage and have no oscillation. Maybe I reading to much into this but something is wrong and I am looking for something to explain why the boat isn't charging right.

In a perfect world the charging system should be outputing 13.5VDC and have no oscillation right??

 

[iwombat]

Re: 1991 Jonson 70 Hp Charging Problems

A charging system with those kinds of design constraints would do that, yet. There are no such design constraints on an outboard. I don't know if you've got a regulated or unregulated rectifier. Either way, some voltage oscillation would be expected. In order to not have that effect, you add big capacitors and voltage stabilization ICs into the mix. I'm kind of surprised your readings aren't more in the 13v range, but that could also be your battery imparting a big load on the system.

One battery or two and what size?

 

[Gary H NC]

Re: 1991 Jonson 70 Hp Charging Problems

What rpms are you testing it at? Get it in the water and test it at 3000 rpm or above.You should then see the increase if its charging.

 

[jtexas]

Re: 1991 Jonson 70 Hp Charging Problems

With AC, the polarity is reversed on a regular cycle. What you should have there is pulsed DC - if it's actually AC then it's broke. A smoothing capacitor would just be extra weight and something else to break down - your battery isn't finicky, it'll eat whatever you put on its plate.

How do those readings compare to your battery open circuit voltage? Did you have any accessories running during your test?

 

[SRobideau]

Re: 1991 Jonson 70 Hp Charging Problems

If the oscillation is normal then i am okay with it. I just expected the rectifier to have a smaller tolerance.

I tested the battery with no accessories running. The 12.5VDC reading was taken while the motor was runing around 2500-3000 RPM.

Could this problem be caused by a bad battery?