No voltage regulator on older Mercury. Can I add one?

[DJ_Allatoona]

1986 Mercury 75hp. Serial: A932083 Everything is great, she starts right up and runs strong and smooth. This is a constantly-evolving project for 10+ years and I've got a PhD in older outboards thanks to this baby. My only remaining issue is the 12V spikes very high when running above 50% throttle. My Garmin fishfinder has a voltage readout and it goes up to 16.5 and sometimes the message "Battery Voltage High" flashes and the unit shuts off. Also, sometimes my in-dash stereo head shuts off when I idle down quickly. So what regulates the voltage, and how can I get that in check? Shop manual diagrams show no regulator, only rectifier. Can I add a 3rd party regulator?

 

[GA_Boater]

Hi Dave.

On your motor the battery is the regulator, same as mine. I bought a combo rectifier/regulator on Ebay or Amazon to replace my Radio Shack rectifier.

My stator only puts out like 6 or 9 amps and I'm not sure about yours.

 

[DJ_Allatoona]

Hi Dave.

On your motor the battery is the regulator, same as mine. I bought a combo rectifier/regulator on Ebay or Amazon to replace my Radio Shack rectifier.

My stator only puts out like 6 or 9 amps and I not sure about yours.

I haven't metered my stator in awhile, only when I replaced it a couple of years ago and checked it was within range per the book.

Could my battery be going bad if my 12v is suddenly spiky? No charging issues or other electrical weirdness so I just assumed rectifier & battery & stator were all doing their jobs.

 

[GA_Boater]

Have you cleaned the cables and posts lately?

 

[merc850]

You can add a regulator to that system and then you can use a maintenance free battery, if you are using one now there is a possibility that the electrolyte will boil off - those systems were used with non-maintenance free batteries.

 

[Faztbullet]

Here..remove old one and install and go.
CDI 193-5114 Johnson Evinrude Rectifier/Regulator 3-Wire (wholesalemarine.com)

 

[sam am I]

Can I add a 3rd party regulator?

Yup.....Nothing special needed. Even if you have 1 amp, 9 amps or 16 or 20 amps, green, blue, red or pink, or whatever stator, the standard stock (or replacement 3 party) Merc 20 amp rec/reg will work just fine and live just ducky in your engine compartment!!.

The two (or 4, 2 pair) wire charge windings on ALL merc stator's are simply just a single (and the newer 3 phase) phase AC output that can vary in current capacity and amplitude generated by a simple magnet whizzing by a simple coil of wires wrapped on iron(a simple magneto if you will), the rec/reg doesn't give a s**t . New or old, there's NO Merc secret magic built into these charge outputs that needs special parts........FAR from it!!.

Rectify the no magic AC to DC, then ya regulate the no magic DC to the Batt.........Easy Peasy!!

Ya just need a rec/reg designed to handle max current (over is fine) the coil can supply at it's max amplitude (over is fine) and handle the enviro (over is fine), hence, no need to re-invent the wheel....

https://www.amazon.com/gp/product/B00BGTMCT6/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Hook the rec/reg's two yellow wires to your stator's two charge windings output wires, tie the rec/reg's blk wire to ground, tie the rec/reg's two red wires together(local sense mode), tie a 20/30 amp inline fuse to that two wire junction and run the fuse's output wire (single wire now) to your starter's batt post.............Hook the rec/reg's gray wire to your tach if needed.

It's is that simple!!

 

[Dukedog]

jus my way a thinkin'... if ya have a "factory" motor that does not come with a regulator and its puttin' out 16+ volts i'd say ya have a problem that a reg. may/may not fix... my understanding that with a "non" regulator motor tha battery serves as tha regulator............. i'd be lookin' at stator and/or battery condition............... jmo.

how many out there that are in "spec" and still runnin' fine without a reg???

 

[sam am I]

With good batt, good connections and the like, Isn't the normal spec on most, if not all non-reg'd at high rev's, can normally be as high as +16.5V?

Non-reg'd (rec only) batt charge systems that use the battery as the regulation unnecessarily and continually charge even a fully charged battery (e.g. OVERCHARGE) have been boiling over batteries, spewing acid water from vent hole cover caps and have been shutting off "now'a days" sensitive electronics since before we landed on the moon and before dirt was even old.....

There's a billion + ruining just ducky perfect out there and most are all still boiling 1950's flooded cells batteries over, can't be used with any current AGM/non-vented "current tech 1980" battery and STILL shutting off our more sensitive electronics...........But since we're in 2021, we've moved forward just a tad, and yes, even for some good.

All IMHO..........

 

[Dukedog]

don't know 'bout you but i've run tha 9's and 16's without a reg. from early production 150 2.0s ta later stem winder 280/300+ 2.5's without seein' 16+ ona gauge (usually 'bout 14/14.5 at most).. or boilin' a battery?.. but thats jus my experience........................

 

[merc850]

Unregulated systems started in 1955 with the Mark 55 and were used up to the '80s and having been a boater for 50 yrs. I have never had a battery "boil over or spew acid" neither have the guys I boated with, the electrolyte would slowly go down over a season but no more than Granpa's old chevy. Maybe this was an omc problem. They added a regulator because of increased use of electronic systems.

 

[DJ_Allatoona]

Maybe this was an omc problem. They added a regulator because of increased use of electronic systems.

I think you have a point here. More (and more delicate) electronics now than they envisioned when this motor was made (1986).