63 40hp Johnson RKL-25D - generator/regulator troubleshooting

I wanted to troubleshoot my charging system...I have 'freewheeled' the generator and it seems ok as it runs as an electric motor. I think my regulator is fried, but not sure. My manual has some troubleshooting tests, but they require engine running at 3/4 throttle....

As it is still too cold outside to run the motor, is it possible to operate the generator with the motor turned off - say by connecting it by pulley to an electric motor or spinning it with electric drill/router so I can check generator output voltage/troubleshoot the system?

If not, I guess I will need to wait until the weather turns warmer...

kimcrwbr1 - good to hear from you....thanks for all the help last year! Tried putting a corded drill on it (socket on top of generator hex nut and chucked into the drill), but it tops out at maybe 2800 RPM and nothing registered at the battery except the original battery voltage.

Can I put a voltmeter directly on the generator and if so, do you think I should see any voltage rise there at 2800ish RPM if generator is indeed working (RPM of generator, not engine)?

Also, when I did the freewheel test on generator with 12.5 volts at battery, the generator drew about 4.6 amps as an electric motor. Do you think that amp draw is in spec? (manual says it should be 5-6amps with 10volts applied?)

take it to an auto parts store and they will spin it and check it for you...

Has the fuse in the box been checked ??

Thanks everyone for the input! Yes, I rechecked continuity and all is good from gen to reg for both arm and field. Also bottom of gen to powerhead is good.


I haven't run suggested test yet where I ground field to powerhead while ignition on and gen spinning, will try tomorrow, but in meantime I have question regarding test. I thought cutout circuit in regulator is normally ' open', so arm and bat terminals open until voltage across arm and ground (at regulator) is about 13 volts then cutoff closes and arm and bat at regulator is connected and current would flow to battery (at least until voltage /current gets too high and reg disconnects reg field to ground). But if reg is fried, then is it possible arm and bat at reg cutoff remain open in which case even if gen working i would still see no change in volt reading at battery. Not sure if question makes sense or maybe I am hopelessly lost on how gen/reg circuit actually works? I will sleep on that and maybe will be clear with fresh eyes.

Yes swahealie to me. My rx200 readings are 2.6ohms on both arm to grd and arm to fld, .7ohms fld to grd.

Also, reran gen test shorting field to grd at gen and taking voltmeter from arm to ground. Only getting 1.5volts output at what was probably about 2500RPMs. Guessing it should be more and my gen is bad too.

going to do more study of swahealie, lots of good info on tractor sites. I agree it is type A circuit, 3 unit regulator. Replacements seem to be running 75-100 bucks, so jumped on one I saw last week for $27 delivered, should arrive soon. That said, I will pull my current regulator off and see if I can figure out why my resistance is lower than yours. Question...when a resistor is goes bad, does impedence go up or down?

Whoops, completely zoned on disconnecting regulator!

Ok, so retook measurements properly...
fld to grd is .8
arm to ground 17.0
fld to arm 16.9

fld to ground seems to high even though under 1, maybe contacts inside regulator needs cleaning. Seems the other measurements are same as yours given normal variation.

that said my meter probes giving me issues, so numbers jumping a bit...will need to pick up new probes as the chinese import ones pretty bad. Will check inside measurements tomorrow.

Havent given up on gen either, will need to see if I can spin it up faster. Last year I know it worked as wire had come loose from armature and vibrated on and off arcing so much it blew some of the threads off of arm post and melted some of the plastic insulation on the post. Hopefully it didn't fry itself in the process.

Have you ever opened up the generator, is difficult get it open?

By way of update...Reviving an old thread here...believe it or not, finally got back to my project after 14 month hiatus from boating (focused on other activities last summer with the family, so never got it in the water). Gonna hit the water this summer, so fired motor up and got er running again, and went about fixing the generating system. Turned out, it was a bad regulator so put in a replacement I picked up last year for $30 and that did the trick! Thanks kimcrwbr1 for your help sorting this one out, better late than never on my completing this repair!