unregulated voltage question

[neversinksmith]

hey guys. finally got my 1973 merc 850 85hp outboard up and running. the rectifier was shot so I replaced it w/ new one. I fired her up and checked voltage at battery and it was showing 18.+ volts of output at just over idle speed. from what ive read on other posts, this is an unregulated power supply, as in there is a rectifier but no regulator. I can confirm that there is no regulator but this doesn't seem right. any other motor ive worked on spits 13-15 volts back to the battery when running. the last thing I want to do is fry expensive components.
what do I do here? thanks

 

[emckelvy]

Sometimes the type of battery used affects the peak voltage; these systems were designed for lead-acid batteries. You can turn on the running lights and that'll probably drop voltage down to a reasonable level. Later model Mercs use a combination regulator/rectifier assembly, and these can be retrofitted to older unregulated systems.

Here's an inexpensive used reg/rect on eBay: http://www.ebay.com/itm/181680245014

Plenty of new ones there, too.

Tech Pic courtesy of my good friend "Dr. Frankenmerc".

HTH........ed

 

[neversinksmith]

can I just go to radio shack an pick up a regulator? how do I go about wiring one into my system?

 

[gm280]

can I just go to radio shack an pick up a regulator? how do I go about wiring one into my system?

NO you can't just pick up a voltage regular at Radio Shark. Because your charging system would blow those little regulator quite quickly due to the fact that the alternator output of your OB engine is beyond the current capability of the norm Radio Shark voltage regular. :nono:

I could actually tell you how to build one with similar electronic parts, but unless you already know electronics, it would be better and cheaper for you to buy one already built for your engine, install it, and carry on... JMHO!

 

[neversinksmith]

well the problem might be my meter. it was laying next to the outboard in 12v mode, not hooked up to anything, and when I started the engine, it jumped to 18.88 volts. when I mover it 3-4 feet away, it lost its reading, got closer and it jumped to 18.88 again. unless my outboard has the capacity to send current through the air, its probably the meter lol. ill try again later after I replace the batteries. uggg

 

[gm280]

well the problem might be my meter. it was laying next to the outboard in 12v mode, not hooked up to anything, and when I started the engine, it jumped to 18.88 volts. when I mover it 3-4 feet away, it lost its reading, got closer and it jumped to 18.88 again. unless my outboard has the capacity to send current through the air, its probably the meter lol. ill try again later after I replace the batteries. uggg

Sounds like you were picking up RFI from the engine. So yes is a way your engine was projecting sporadic voltages through the air. But not reliable voltage reads at all... Make sure you set the meter to the DC scale and to the 20 volt scale as well and read the voltage at the battery. Let us know how that works out...

 

[bruceb58]

I wouldn't be too worried about that. Meter inputs are very high impedance so the inputs can float to almost anything. Put a 1K resistor across the input and it will read 0 again. Your meter leads are acting like an antenna.

First I thought it was your meter sampling rate but then you said it was just sitting there doing it.

As far as what regulator to get, send an email or call these guys. They will know what is best for your engine.
http://www.cdielectronics.com/
http://www.boatingmag.com/converting...harging-system

 

[Texasmark]

Not hijacking the thread as it looks like it's been answered, but on your specific engine:

I bought one New back in '73. Had it about 5 years and fished every time I could and most every weekend (I could sneak out of the house and honey do's). Other than gas and oil, I did nothing to that engine in that time span and it never let me down. Probably the finest engine I ever owned. I used to fish in the winter as much as the summer and I used to get a kick out of launching first thing of the day. Numerous other anglers were fiddling with their engines, trying to get them started or run right during the prime fishing time. I went fishing.

I'd squeeze the bulb, fast idle up, back the trailer into the water, jump in, spin her over for about 15 seconds (in the winter) and "varoom".....she was alive.

Enjoy a great engine.

Mark

 

[neversinksmith]

step one in troubleshooting electrical issues:
make sure your meter is working properly
my charging system is fine, thanks guys