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Yamaha 25hp autolube charging fault

M

Melvin Hall

Member
Have tested the battery voltage before starting the engine, 12.9v, it did not raise when running the engine at idle or at full throttle, so have come to the conclusion it is not charging.

If the most likely problem is with the rectifier, I would need help identifying it and how to test it?

Any help would be much appreciated, thanks.
 
What does the autolube part have to do with a no charging issue?

What is the complete identity of the motor?
 
Is is a yahaha 25hp 2 stroke autolube, no year marked on it but must be at least 10 years old.

Only details i can find are 25NEO 6L2 L 451571.

Have tested the regulator and it tests fine, 0.5 ohms continuity when tested one way, open circuit when testing with the leads the other way around.

Where do I go from here?
 
Get a copy of the service manual. It should provide the procedure for testing the rectifier/regulator. In general, the output should be approximately 14.5 volts. If no output then check the lighting coil for specifications and proper AC voltage output.
 
Better to check for continuity using the continuity function of a VOM rather than the resistance/ohm setting.

From the green lead to the green lead their should be no continuity.

From either green lead to the red lead there should be continuity.

From red to either green their should be no continuity.

From black to either green lead or the red lead there should be continuity.

The check for the lighting coil is .28 ohm from green lead to green lead. Make sure that neither green lead is shorted to ground.

The output spec for the lighting coil is 10 volts or more at 3000 RPM and 15 plus or minus 1.5 volts at 5500 RPM. Remember that the output of the coil is AC.

Generally, if the lighting coil is producing specification voltage but the rectifier is not then the conclusion is that the rectifier has failed. But make sure it has a good ground path.
 
Thanks.

I was using a multimeter to test the resistance, what is a VOM?

The two green wires on the rectifier come from under the flywheel, is that the coil from the alternator, lighting coil you mentioned?

Can these two green wires be disconnected from the rectifier and tested when the engine is running?
 
Melvin Hall said:
Thanks.

I was using a multimeter to test the resistance, what is a VOM? A multimeter.

The two green wires on the rectifier come from under the flywheel, is that the coil from the alternator, lighting coil you mentioned? Yes

Can these two green wires be disconnected from the rectifier and tested when the engine is running? Yes
Click to expand...


See comments above.
 
Thanks,

Tested the conitinuity of the lighting coil and was less than half an ohm.

Measured the coil output voltage, was about 7vac at idle, raised to 19vac flat out.

coil was not shorted to earth.

Would this point towards the rectifier then?

The battery was at 13v with the engine off, with it running it did go up to 13.2v at idle, 13.6v flat out.

Is there a maximum capacity size the battery should be?

With the engine running i can get the fishfinder to switch on, but when i try to turn on the vhf or lights or anything else the fishfnder goes dead.
 
Keep in mind that the output of current from your rectifier is very small. More than likely less than five amps at wide open throttle. It sounds as if the system is working.

From what you are describing I would suspect the problem is related to the battery or the wiring. Even if you had no electrical output at all from the motor a good battery and good wiring should be able to provide enough current to operate a fish finder, a VHF radio and some lights for a period of time without dropping its voltage to the point that the fish finder turns itself off due to low voltage. One test of a battery is a load test. An electrical load of XYZ amps is applied while the voltage of the battery is observed. The voltage is not to drop below 10.5 volts.

You can take the battery to an auto parts store and get it load tested for free. You yourself can inspect all of the electrical connections to make sure they are clean and tight.
 
Thanks,

The battery i got with the boat was a pretty heavty jcb battery, i thought there might be a problem with it so i bought a new 40ah car battery and tried it, just seemed to work the same. I can get the fishfinder to work, but when turning on anything else it just goes dead.

I have connected in two solar panels to try and raise the voltage a bit, it seems to help a bit but not much.
 
Replace the rectifier and see however if you want to throw money at the problem.

I don't think it is is the rectifier. Poor wires or electrical connections will cause the problems that you describe. Particularly the ground wiring.
 
I tested the battery and then tested at my control box, there was more than a half a volt difference, so i suspected the supply cable.

I connected a heavier cable from the battery to the control box and tested again.

This time there was no voltage drop, tried switching on my functions and everything worked ok, so the cable must have been the problem!
 
I've rewired the cabling to thee control box and all my functions can work now ok.

This has lead me onto my next problem though. When the vhf is on, and i turn on the fishfinder the vhf picks up the interference, clicking noises. Is the way to clear this to move the transducer cable away from the supply cable of the vhf?
 
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