Evinrude Yachtwin 6 charging circuit

[schuhjm]

Hi folks,

New to the forum here...

My GF just bought a ranger 20 that I've been diagnosing some minor electrical problems on, and I have a quick question on the Yachtwin charging output.

I had to redo the connector through the transom, and having done so, I tested the output of the charging terminals from the outboard. It was measuring around 4.5 volts. Not knowing the motor, or having a manual, I was wondering what type of circuit I'm dealing with. Is it converted/regulated/DC/AC? As far as I've been able to discern, the connection is made direct to the battery, and I don't see any bridge or other regulators behind the switch panel so I suspect it's supposed to be DC ~12V, but that's not what I'm getting

So far, I'm leaving it disconnected until I know what I'm dealing with.

Any advice appreciated.

J

 

[SycloneDriver]

a/c or d/c

4.5 volts ac or dc? at idle?

The Yachtwin looks to be an older motor so it may have an a/c output. A simple rectifier will convert the output to d/c.

 

[Bill Roosa]

Hey J
The proper term for GF who gives orders which you are expected to carry out is "Admiral." ;-)

Your outboard is most likely 12ish DC. A lot of small mills have magneto ignition. This type has the “alternator” is broken up into an ignition circuit and a charging circuit.
Low output volts can be caused by a couple of things:

Not enough RPM – rev the motor to max RPM and retest

Diodes have gone bad - With the motor off and wires disconnected measure the resistance of the two charging wires. You should get a low resistance in the charging direction (5 ohms or less) and a high resistance when you reverse the leads. There should be a diode(s) in the alternator that prevent back flow of current from the batts through the alternator when the motor is off. If you don’t have a high resistance this would be an indication the diodes are blown.

Since the engine runs and not knowing how handy you are around the inside of an engine I’ll make the following “observation”:
Consider how hard it would be to tear apart the engine and find the problem. Balance that against buying a decent deep cycle battery (100 AH) and charger and just forgoing the engine charging systems all together. This assumes you have access to shore power BTW.
My reasoning is as follows: you have a day sailor and are probably not going to be spending lots of time over-nighting, you don’t have a reefer or other big electrical loads that would require lots of storage and generating capacity. The outboard will not handle this in any case. You may already have a 100ish AH battery bank and charger. If all you need to power is the VHF, stereo, the nav lights for a few hours each trip and the instruments then you really don’t need that outboard alternator and can just run off battery power till you get back. Then just plug in and let shore power recharge the batts. FWIW.

 

[FourPoints]

For the reasons Bill mentioned, you may not care to actually implement this, but at the least it should explain a few things...

http://sailingit.com/blog/boat-projects/outboard-voltage-regulator

 

[schuhjm]

Thanks,

Ah yes, GF has already been referred to as "Admiral"...

And, you are correct on the usage, we will be only day-sailing, and semi occasionally at that. There is a good deep cycle battery, so the charging system is not at all critical. Our needs are only instruments and occasional running lights. I just want to make sure things are working.

Regarding digging into the engine, I am not planning on doing that. I am an EE, so the electrical is in my realm. I just didn't know what I was looking at, and wanted a quick thumbnail on the output.

I think I've got enough to go on thanks to the responses.

Thanks,
J

 

[kenn]

As long as the outboard's charging coil is working (test the voltage and current into a 12v lamp and/or rectified and across the battery), your EE kung fu will let you determine how much or how little effort you want to put into a charging circuit.

I'm still playing with the charging output from our Suzuki 5 hp outboard, with a cheap 10A meter in series so I can monitor the charging current. I may add a power resistor to limit the current to a safe 'float' charge value, then put a switch across the resistor to permit full-current charging when I need it.

The Suzuki manual recommends using just a standard flooded cell storage battery, as opposed to a sealed AGM or gel type, because the flooded-cell type is more tolerant of overcharging.

 

[Fly_H23]

Most small outboards won't charge until above 2000 rpm. You should see little or nothing at idle and +12 dc and/or greater as rpm rise over 2000 rpm.

We sold our gas outboard and went electric with 30 watts solar on a deep cycle 105 amp battery and 50 lbs thrust 12 volt trolling motor on our Hunter 23. It pushes it 3-4 mph at 70% thrust giving a range of 4-5 hours on a full battery.