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  Converting to Unregulated Charging Circuit

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Author Topic:   Converting to Unregulated Charging Circuit
jero posted 06-29-2006 02:08 PM ET (US)   Profile for jero   Send Email to jero  
The voltage regulator and rectifier on my 1984 Evinrude 140 have quit on me. The replacement part is [over $250], but just a plain old rectifier is about $30. This motor came with either a regulator and rectifier or a plain old rectifier, depending on the option for power trim My motor has power trim.

Give me a suggeestion on coverting to just a plain old rectifier from a rectifier and regulator. I'm not worried about the higher voltage, as I don't run any electronics. I just need to (minimally) charge the running battery.

Can I do this or am I nuts?

Whaler_bob posted 06-29-2006 03:03 PM ET (US)     Profile for Whaler_bob    
Iboats has the Sierra replacment for $183. I found another place for $173. Thase were the first two sites I checked, you could probably do even better with more searching.
aja posted 06-29-2006 03:51 PM ET (US)     Profile for aja  Send Email to aja     
Be careful of running an electrical system with no voltage regulator since even if electronics aren't connected, you will boil electrolyte out of your battery when running for any amount of time. May be cheaper to buy the right parts than a pallet of batteries.
jimh posted 06-29-2006 09:59 PM ET (US)     Profile for jimh  Send Email to jimh     
I do not have first-hand knowledge of the electrical configuration in your engine, but my guess is that if the engine was ordered with the option for power trim, the capacity of the stator may have been increased to deliver more charging current. This required a regulator to control the voltages.

The engine without the power trim option probably had a stator with less output. When connected to a small charging current, a wet cell lead-acid battery can act as a voltage regulator, and the battery itself will hold down the peak voltage somewhat. However, it you have the larger output stator, the stator output may be too much for a battery to self-regulate.

As mentioned above, running the larger stator without a regulator on the output may result in excessive voltage which could be harmful to the battery itself.

bsmotril posted 06-29-2006 10:24 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Do a search in this forum about 6 weeks back. An OMC tech posted a part number for the new style regulator which is about $100 that can also be used in those motors. Too bad I found out after I bought the expensive one. Note, you have to pull the flywheel to get access to replace the regulator, whichever one you choose. So you'll need a wheel puller tool too. BillS
jimh posted 06-29-2006 11:03 PM ET (US)     Profile for jimh  Send Email to jimh     
It is also possible that the motor with the unregulated charging circuit had a stator whose coils tended to saturate at a certain engine speed, and thus the stator coil output was more or less self regulating. The model with the higher output stator coil will likely be able to produce greater voltage output.
jero posted 07-02-2006 03:13 PM ET (US)     Profile for jero  Send Email to jero     
I ordered the $30 part, and put it on to try it out. Seems to work just fine. It charges @ 12V at idle, and about 14-15 volts WOT. Now my problem is how to figure where to hook up the tach so it works again...
jimh posted 07-05-2006 09:01 AM ET (US)     Profile for jimh  Send Email to jimh     
It is practically universal that the tachometer pulses are derived at the input of the rectifier. The gray wire should attach to one of the AC connectors on the rectifier. In this way it will produce a half-wave rectified output.
seahorse posted 07-05-2006 08:21 PM ET (US)     Profile for seahorse  Send Email to seahorse     
Oh Goodie, I get to slap Jim's hands for his last post !!! :)


Hooking the tach lead to one of the yellow wires does not produce a 1/2 wave rectified signal. The yellow wires are strictly AC voltage, not rectified.

the tach lead should be connected to the yellow-gray wire as that is what the factory does.

jimh posted 07-05-2006 11:11 PM ET (US)     Profile for jimh  Send Email to jimh     
The stator does output an alternating current/voltage. However, the leads from the stator, when connected to the rectifier, become part of the rectifier circuit. If you look at the signal that results you'll see the effect of the rectifier. The tachometer pulse signal is clamped (by the action of the rectifier) at about one volt above the battery positive and similarly clamped (by the action of the rectifier) at about one volt above ground. If the rectifier were not attached, the signal would be quite different.

Are there three wires involved? Two yellow leads and one yellow-gray?

jero posted 07-06-2006 01:40 PM ET (US)     Profile for jero  Send Email to jero     
Thanks for all the replies folks, I'm glad I stumbled upon this [collection of information]

My old rectifier/regulator had four wires; yellow/grey, yellow, violet, and red. The new rectifier only has two yellow, and red. I believe the tach connected to the purple lead, but as you can see, I'm short a lead and didn't want to fry anything... I'll try connecting the tach to one of the yellow, unless yall think that would mess somthin up.

jero posted 07-10-2006 02:31 PM ET (US)     Profile for jero  Send Email to jero     
Connected the tach to the yellow/grey wire. Works great. Thanks.
jimh posted 07-10-2006 10:04 PM ET (US)     Profile for jimh  Send Email to jimh     
The VIOLET lead (purple) has nothing to do with the tachometer pulse signal. In installations which follow the ABYC recommended color coding, the conductor with VIOLET insulation carries switched 12-volts that is present when the ignition switch is in the START or RUN position. You can see a listing of the color codes for marine electrical installations in the REFERENCE section.

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