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Over charging ?

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oldguy46

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I'M OLD SO BARE WITH ME PLEASE. THE BATTERY IN OUR 1988 SEARAY(100hp) SHORTED OUT SO I REPLACED IT WITH A NEW BATTERY BUT NOW THE AMP GAUGE GOES ALL THE WAY TO 16 AMPS AND DOES NOT COME BACK DOWN. IT WENT TO THE MIDDLE (13amps) BEFORE. A AUTO MECHANIC FRIEND SAYS NOT TO RUN IT , THE LOCAL MARINA QOUTED ME A $112.00 TO TELL ME WHAT IS WRONG & PROBABLY ANOTHER $200-300. TO FIX IF PARTS ARE AVAILABLE....WILL REALLY APPRECIATE ANY CONSTRUCTIVE ADVICE...MIKE
 
Since you don't say (but posted in the Mercury Outboard section), I will assume you have an outboard motor on this boat.

Your motor will recharge your battery by (controlling) the charge through either a rectifier (which simply converts the power the charge portion of your ignition produces to DC and sends it "un-regulated" to the battery) OR a regulator (which converts the power then "regulates" it so that it sends a more stable/constant charge to the battery - usually somewhere in the 13.5 volt range, give or take a bit).

Now, while it isn't unheard of that a rectifier would "throw" 16 volts down to the battery, from your post it's obvious that this was "not the norm" before you have the initial battery issue.

What I would suggest happened was 1) you toasted your battery 2) because there was "nowhere" for your system to send the charge it toasted your regulator/rectifier 3) you replaced the battery but the toasted regulator/rectifier is still there and it's trying to "cook" your new battery.

If your motor is a 1988 Mercury 100 horse outboard (came packaged with the boat when new?), then it has a "regulator".

The OEM part is about $200. The same part from Sierra (an aftermarket company) goes for about $125. They are held on by two screws and have about half a dozen wires with bullet connectors (to connect back into the engine wiring). It's about a 10 minute job to change. So yes, at a Merc dealer you would be looking at 300 to 400 bucks (parts plus a few minutes of testing and a few minutes of replacement - billed at a 1 hour minimum shop charge).
 
There is a rectangular box held on with two screws but when i ran the part number it was for low oil indicator. Other than that i can see the starter relay and another piece held by two screws but with three posts with 3or 4 wires held on by nuts. From a couple diagrams i looked at it appears to be a rectifier. The battery seems fine and starts up the motor, i checked it with charger and seems ok. Yes it is the original outboard but have not been able to find the exact serial # on line (b292347). Is the rectifier also the regulator or is it a seperate unit? I really appreciate the help, old age,fixed income,cancer does'nt leave alot to keep things going .
 
Your 1988 100hp Merc falls into this serial number range:

http://www.marineengine.com/parts/mercury-outboard-parts/100-4-cyl/0b209468-thru-0d283221-usa

Here's the electrical components breakdown:

http://www.marineengine.com/parts/m...09468-thru-0d283221-usa/electrical-components

You'll note P/N 38, the rectifier. This is the old-fashioned bridge rectifier without a regulator. Voltage will vary with rpm as the O.P. described. On this engine, when a rectifier is used, P/N 39 is also used. Called either a "terminal block" or "rectifier", it provides a tach signal via the middle connection.

What's more likely is that you have a combination rectifier/regulator installed. See P/N 40. This was available as a retrofit for those motors originally having the old-style, non-regulated rectifier.

Merc does it one way, using lots of wire and retaining the "terminal block" where the tach wire connects:

http://www.marineengine.com/newparts/part_details.php?pnum=MER815279A+2

Aftermarket does it a different way, using a rectifier/regulator that has its own "tach output" wire that hooks up to the engine's tach sensor wire:

http://www.marineengine.com/newparts/part_details.php?pnum=SIE18-5741

http://www.marineengine.com/newparts/part_details.php?pnum=CDI194-5279

There's one more listing, from CDI electronics, which does not have a tach sensor wire built-in:

http://www.marineengine.com/newparts/part_details.php?pnum=CDI193-5114

It's listed as a functional equivalent replacement for the standard rectifier, except it's regulated.

For this one I'd assume that you'd keep the "terminal block" and its tach connection. You'd have to figure out a mounting point for the CDI unit as it doesn't look like it has the same mounting holes. But it may be small enough to fit the same spot as the OE rectifier. And the connections are the same as the wires would be to a rectifier, 2 yellows from the stator and red +12V.

For completeness and ease of installation, the Merc upgrade is a shoe-in. It has a nice aluminum mounting bracket for the rectifier/regulator, all the wiring you need, mounting hardware, and a new terminal block. But it is more $$$ than the aftermarket parts.

If you can fab-up a mounting bracket, or already have a regulated unit on there and just need to replace that, the CDI or Sierra rect/reg's with tach output (grey wire) would do the job for less $$$.

If you have the very large rect/reg with fins shown as P/N 40 in the diagram, there may be enough room to mount the later-style, smaller rect/reg right in its place without having to build a mounting bracket. And if that old rect/reg uses the terminal block for the tach output, you don't need the rect/reg with grey tach wire and could use the inexpensive CDI rect/reg I described above.

It would help if you posted a picture of the Stbd side of the motor, showing the electrical component's mounting plate, without the plastic cover. Then we could better figure out what you have and what needs to replace it.

And if you want to be even more cornfused, check out P/N 43 which is yet more rectifier/regulators! Crazy, huh? :confused:

HTH............e
 
you said 16 amps...did you mean 16 volts?

if you have a rectifier only charging system and replaced the battery with a sealed maintenance free one the voltage will go to 16 volts or even higher...this is bad and will eventually blow the rectifier and possibly electronic gear...you have a choice...either replace the rectifier with a regulator or replace the battery with the type that you add water to maintain...
 
Will try to upload pics of the motor, yes i am totally confused at this point. I have removed the rectifier and tested it according to instructions with a multi tester and it checked out ok. If i have the unregulated motor what failed to cause itto start overcharging as it was not a problem befor?
 

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What type of battery are you using? Do not use a closed cell or maintenance free battery to begin with. Either regulated or unregulated you must use a flooded cell lead acid battery. There is no place for the added voltage to go with a fully charged maintenance free battery. If you have a old style car battery in good condition handy put it in and see how it works. You can allways run some high amp draw appliances to use up the excess power produced with the high revving outboard motors.
 
THE BATTERY IS A JOHNSON CONTROL MARINE BATTERY AND ALTHOUGH IT SAYS ' maintenance free ' IT HAS THE REMOVABLE CAPS TO ADD WATER. ALSO NO PROBLEM WITH THE OLD BATTERY THAT WAS THE SAME EXCEPT HIGHER CRANKING AMPS UNTIL IT QUIT WORKING.
 
I can see where this is going. Just because it had the same battery does not mean it was correct. Your probably better off letting someone else figure it out.
 
Ok so i swapped out the new battery for an older one and the results were the same....went to 13 for about 5 seconds then buried at 15-16.
Le it idle for a few minutes but showed no sign of coming back down.
 
oldguy46 said:
CHECKED THIS OUT BUT LISTED FOR 1993 & UP, 15hp....I HAVE A 1988 100hp motor..?
Click to expand...

That's the generic description, if you drill down to the part numbers you'll see that the Merc standard ol' square bridge rectifier (like yours) is one of the parts this one can replace.

Your old-style charging system only puts out about 10 amps, so No Worries, Mate!
 
oldguy46 said:
No tach wire
Click to expand...

Take a look at the installation instructions posted; they say to take the existing tach wire and connect to one of the yellow wires off the rect/reg unit. If your tach wire hooks to a terminal block, it will no longer be connected there, but directly to one of the stator yellow wires.

If you're saying there is no tach wire at all on the motor, that's a different story. Maybe post a close-up picture of your existing rectifier, with the obscuring wires pulled out of the way so we can see what's connected.
 
I'm going with ed-mc suggestion as soon as i can afford it as it makes the most sense to me.
There is one more questn i needhel with and that is about marine batteries. I have seen alot of warnings
about low or maintenance free batteries when used with my motor. I have always thought they were a sealed
battery that you could'nt add water/acid to. The new marine deep cycle battery in the boat now has removable
caps and you can see
 
I am going to repeat myself...if you have a rectifier only charging system and the battery says maintenance free then you need to check the owners manual and get the correct battery...it is a boaters habit when replacing a battery to get the best he can afford....that usually is a maintenance free one..this is a mistake with the rectifier only system...this is a known problem and we get many threads on this over time...
 
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