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Mercury 50hp 1985 overcharging

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rockinhitz34

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Recently hooked up a gps/fishfinder and it shuts down under power, but runs fine off the battery. Hooked up a multimeter to check voltage under power and realized as throttle increased so did voltage until the gps shuts down to protect itself. What can I do to remedy the situation? Do I have an overcharging problem?

Thanks!
 
Most of the older models have rectifiers and not voltage regulators.

With a rectifier the voltage (and output in watts) goes up and down with the rpms - more rpms, more voltage/watts. The rectifier on my 15 horse can spit out in the high 16 volt range when she is running wide open.

In a rectifier system the battery acts as the regulator so you can't run your electronics directly off the stator output.

But if your rectifier is sending much more than 16 volts to your battery it may be on it's way out and should be changed.
 
Its a 4 bridge rectifier its either good or bad and it only puts out what it receives from stator.Check your battery or install a rect/reg
 
My first post, so bear with me. (my name speaks for itself) older than dirt. I hope I'm doing this in the correct place, as I'm new to this forum and don't want to break any rules.

I figured since the subject is on Rectifiers I'll post a question concerning my son's recent purchase of a 1978 Mercury 800 80 HP 4 cylinder 2 cycle outboard motor. When he finally brought it to me for doing the work needed to get it running, (after which he'd had several others attempt to get it running) I didn't even remotely know what I'd gotten myself into. A real project for certain! Especially for an old man nearly 80 and in bad health. However after coming upon Marine Engine, the rest of getting it up and running was going fairly smooth, although very time consuming. After removing the cowling I first found the Flywheel was totally loose on the crankshaft. My son informed me he'd never had it off, nor had anyone else in checking out the motor with him. So here is the total of what I've done to date. First was the fact that the folks in power (EPA) had the gasoline turned into Ethanol (the ruination of everything from gasoline hoses and most everything else that previously ran on good old leaded gasoline) I first torqued down the flywheel. then I found both of the "Center Square Bowl Carburetors" were completely plugged up with all of this green crap. So I totally rebuilt both. The engine would then start up but only run at idle. and would die upon attempting to throttle it up. So, I checked the Stator and found the high speed wires to be open (no continuity). After installing a new stator that cured that problem, however it was still running horrible at best. Next I found out the trigger had an intermittent problem so I replaced it. Problems all solved and it runs like a champ. However, in checking out the Rectifier, (just to be sure of it being ok) I found it was also bad. One of the diodes had opened up where the Stator output wires (Yellow in my case) going to it. So that's where I'm currently at. I dug out all of the Liquid Rubber crap to find out exactly what was going on inside it. (first off, I'm not a parts replacement artist as some folks are. I'm the type that wants to know why whatever fails and repair it if at all possible. I also must admit although I've been an Auto Mechanic most of my life, I'm NOT a marine mechanic by any stretch of the imagination. What I've been in life was from hard study of what I needed to know in order to get the job done, regardless of what that job happened to be. So there you have it. My first post and hope you found it a bit interesting. Thanks for allowing me this time, and I really want to thank Marine Engine for all of their fast shipping of parts I bought through them. These folks are some of the best I've found. Thanks again. Hope I didn't bore you too much!
PS: I wanted to send a picture of the inside of my Rectifier that I've soldered the broken leg back on, and also ask if anyone can tell me if testing the + Positive Terminal to case Ground should it show open when testing with an ohm meter (in either direction) or if it too should test as a Diode would. forward bias direction allowing current flow and reverse bias preventing current flow?

Thanks to any and all who respond. It's appreciated.
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I take my hat off to you.I hope to be able to walk if I ever get to eighty never mind be able to fix and repair 80 HP Mercurys,mine is a '69 Merc800/80. Here is a link to testing the rectifier http://myoutboardengine.com/rectifier.html .I hope it is of some help to you.
There is a post,somewhere,on how to use a $5 rectifier from some of the electronics stores as opposed to the $35 OEM on.And with your skill it wouldn't be difficult to fit a regulator inline on it.Have thought about this for when my rectifier goes.
 
Sorry it took me so long to respond. Thanks for the site, that is just about how I tested mine. However that didn't show going from the + post to ground either. However, after more evaluation, I'd say my Rectifier is somewhat of a Rectifier/Regulator. Here is why I feel it may be (at least) A Bridge Rectifier would have 4 regular Diodes, whereas this one has two of those and the other two are Zener Diodes therefore it sort of acts to keep the voltage around 14 volts (or around that amount) so you can run all of your optional electronic devices (directly off the battery) without worry of them burning out from too much voltage. I'm going to try (I say try) to upload a couple of pics if I'm capable of doing so, in order to let you see inside of one. I'm going to be digging it out a little better as I noticed that those Button Diodes have numbers on them. They look exactly like the cell batteries inside of a 7 volt battery when you take one of them apart. Quite interesting. I made a drawing on a napkin as well. Ok, here goes a try of uploading. View attachment 18236
PS: I'll have to find my drawing before I can upload it. Hope this is clear enough to see. I'm a bit shaky when holding a camera steady enough for it to focus as it otherwise would.:cool:
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fastjeff said:
As in fried!

Jeff
Click to expand...

That's the problem, it's really NOT fried. It has one leg inside that broke loose from where it gets soldered to the post. So it wasn't from overheating it was probably from someone over torqued it and pulled it loose. If I soldered it back and filled (what I chipped out to have a look inside) it back up with liquid rubber, it would be the same as new. However, I'm not going to do that. But I'll agree with what you said, in it looking to be fried. But again, that's only from me sitting here with nothing better to do, than chunk out that liquid rubber tiny pieces at a time with needle nose pliers..:cool: Hey old folks like to have a look at what actually took place.

Question: Does Marine Engine have rectifiers? I'm bad at looking things up online. The motor's serial number is: 5008355 and this site (and many others) can't look up that number for whatever reason that is, so I use from that number up to where the cutoff for that model ends.

PS: I really do appreciate your reply. Just wanted to let you know it only looked as if it was fried. But I most certainly did appreciate your post. I'd have felt the same if I seen something that looks as it does now.:cool:
 
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faztbullet said:
That's just a rectifier no regulation...
Click to expand...

Could you tell me exactly why there are two Silicone Diodes and Two Zener Diodes if they are not for a slight amount of regulation? A Bridge Rectifier usually uses 4 Silicone Diodes. Just wondering as in old men like to learn the why's of things as they go.:cool:

Thanks a whole lot for your reply. Much appreciated
 
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