1986 Johnson 90hp V4 starts & runs great but does not charge the battery

[Kit_B]

I have a 1986 Johnson 90hp V4 motor that runs great & goes like crazy...
But, it doesn't charge the battery.
Can someone please tell me how to correctly identify whether the problem is my stator or my regulator/rectifier?

Thanks, in advance!

 

[emdsapmgr]

Your engine probably needs a combination rectifier/regulator. It mounts on top of the block and is water cooled. Original part number 395391. Superceded to part number 395204. This device recharges the battery and also creates the signal to drive the tach. The rect/reg life can be significantly shortened if the main leads to the battery get loose during summer operation. (Keep the nuts tight on the battery.)

 

[Kit_B]

No Title

Thanks, for your response.
Can anyone tell me how to test the rectifier, before I spend roughly $200?
Is a DVA required?
Will testing resistance between yellow wires, followed by resistance between yellows & ground be sufficient?

I have a meter like the attached photo & I'll do some testing, tonight.

I have read the CDI document, but I don't have a tach or a DVA.

 

[emdsapmgr]

One way to test the rectifier/regulator is to see if the tach works. Yours does not. Strike 1. You can also put a voltmeter across the battery while the engine is running. Once the engine runs for 20 minues, normally the battery will start to charge, and should read maybe 13.5 volts. If it is still reading 12.4 or 12.6, that's just normal battery voltage and does not indicated any charge from the engine. Strike 2.

 

[Kit_B]

Does the engine really need to run for 20 minutes, before I see an increase in the voltage?
Shouldn't the engine start feeding voltage back, right away?

 

[Fed]

If you start with a fully charged battery you should see an increase straight away.

Is it a regulated system or rectifier only, that's why putting up a model number will get you answers.

 

[Kit_B]

Sorry...It's a J90TLCDC.
It's equipped with a water-cooled 35A rectifier/regulator (part #395204), as emdsapmgr has kindly pointed out.

I took it on the water & ran it for nearly an hour, last night.
There was no increase in the battery charge, aside from a slight recovery from the starting.
It remained at a pretty constant 12.2V, throughout.

 

[jakedaawg]

I agree that most likely is the rec/reg. Don't forget to order the gasket that goes between the assy and power head otherwise you will have a leak. Just replaced one today as a matter of fact.

 

[jakedaawg]

The ohms test is good enough to rule out lighting coil 99 times out of 100. If you're paying $200 it's way too much. I just bought one for $90 and change but I get a good break. I think ~$118 is list from brp.

Edit. Disregard, different part number. Sorry

 

[Fed]

Using the same method test your car and see if you get the expected result.

Then test the stator, yours should be 9 Amp.

 

[Kit_B]

Bench tests show good stator & a bad diode in the rectifier/regulator.
Thanks, everyone.

 

[Kit_B]

I replaced the rectifier/regulator with CDI #193-5204, from a local source.
The part ended up costing me $185.
The work was made incredibly easy, with an impact wrench.
I would recommend that anyone attempting this replacement use an impact tool.
I also used a cheap flywheel puller, from my local auto parts store.
The flywheel came loose, quite fast.

Installation was a breeze.
Tonight, I'll try to take it out & make sure everything is working like it should.

 

[interalian]

Used a torque wrench to install the flywheel nut I hope.

 

[Kit_B]

Used a torque wrench to install the flywheel nut I hope.

Indeed.

 

[Fed]

How did you bench test the rectifier/regulator Kit?

Hope the on water test goes well.

 

[Kit_B]

No Title

The bench test was done, following the attached instructions from CDI.
I ran the motor on muffs, last night.
There were no leaks at the gasket & the charge immediately improved.
With any luck, I'll be able to run it on the water, tomorrow afternoon.