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Author Topic:   Using Unregulated Battery Charger Output from Older Outboard Engine
MarbleCharlie posted 07-27-2015 12:50 PM ET (US)   Profile for MarbleCharlie   Send Email to MarbleCharlie  
Hi all. I have a 1992 Mercury 40-HP four-cylinder two-stroke-power-cycle two-carburetor electronic ignition outboard engine. My outboard was not charging the battery at all. I replaced the rectifier and now the voltage shoots to 16 to 18-volts under full throttle. So I looked up the part for the regulator in the mercury parts catalog and ordered that. It won't fit, in fact I can see the mounting holes for it above and below the rectifier.

So on closer inspection, the parts catalog only shows a voltage regulator under "design II" and the service manual stated that some motors have the regulator/rectifier combo, and some just have the rectifier (you still with me?). Am i correct in assuming that my design has no regulator? Is it okay to run just a battery and lights, no radio for now without a regulator? Can I adapt my current regulator-rectifier combo into this motor? The parts catalog lists a different starter solenoid for "design II". Is there a generic regulator I can plumb in there?

Thankfully I can return [the rgulator-rectifier I bought] and it only set me back $40 versus $180. My [outboard engine being discussed has serial number] 0D106203.

goldstem posted 07-28-2015 12:19 PM ET (US)     Profile for goldstem  Send Email to goldstem     
You [outboard engine has] no regulator. This is very common for smaller, older outboards. You can run fine with no regulator. The battery itself acts as a regulator. You should probably stick with good-old-fashioned batteries. I find so-called dual-purpose or a deep-cycle works best. Your 40 is pretty easy to turn over for starting. Periodically check the water level in the battery, as the high voltage can boil out some water. Depending on how often you use it will dictate how often you should check the battery level. Usually once mid-season and again at the end of the season is sufficient.
jimh posted 07-28-2015 02:39 PM ET (US)     Profile for jimh  Send Email to jimh     
Electrical circuits are wired, not plumbed.

Be sure to use a flooded-cell lead-acid battery that is not sealed. You will need to periodically add water to the battery due to chronic overcharging and poor voltage regulation of the charging voltage.

A good Mercury service shop that is familiar with your vintage of outboard engine can tell you if the non-regulated charger can be adapted to a regulator.

As mentioned, for decades there was no voltage regulation in small outboard engine charging circuits. People just added water to the battery to compensate for the electrolyte becoming boiled off.

I don't know of any add-on generic voltage regulators for 12-Volt charging circuits of old outboard engines, but that does not exclude the possibility there might be one.

Maybe this one would be useful: dp/B000C5H8RQ

R DAVIS posted 08-01-2015 11:14 AM ET (US)     Profile for R DAVIS  Send Email to R DAVIS     
One thing to keep in mind.

Although most electronic devices used in small boats such as GPS, sonar, AM FM radios, lights, etc. are OK to run as high as 16 to 18 volts, some cell phones can be damaged at that level.

If you decide to add an outlet or plug for phone charging, be sure to check your phone owners manual for maximum permissible voltage. Note: Although most 12 volt incandescent bulbs will work OK at 18 volts, they will burn out more frequently. If using LEDs, check the spec sheet for max voltage.

seahorse posted 08-01-2015 04:36 PM ET (US)     Profile for seahorse    
Check with CDI Electronics < > as they designed a rectifier with built-in regulation for many outboards that were the old constant charge only types.
Tom W Clark posted 08-01-2015 04:52 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark

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