1990 90hp Merc charging question

[dingo99]

Does this motor contain a regulator / rectifier or just a straight rectifier. I am as well having an excessive voltage problem and am wondering if it is regulated or do i have a battery problem?

 

[Laddies]

Re: 1990 90hp Merc charging question

It's tough to tell without a seriel number but if you look at it and it has 3 studs its a rectifier and 5 wires it's a regulator

 

[Texasmark]

Re: 1990 90hp Merc charging question

On the regl, my maint manual shows 5 + gnd for a total of 6.

If manual start, OEM has no rectifiers, and no regulator. That Stator output was only for running lights, unless you bought the rectifier kit. Merc never told us if a regulator was part of the "Rectifier Kit" used to charge a battery; but probably was. The stator was Black and 9 ampere.

The elect start version of the 90 hp, with the 5+ gnd regulator/rectifier was hooked to a red stator for 16 amperes of regulated direct current to recharge your batteries and run your running lights.

Want more, ask!


Mark

 

[fatherervin]

Re: 1990 90hp Merc charging question

Can someone breifly explain the difference between a rectifier and a regulator?

Thanks,
FE.

 

[Texasmark]

Re: 1990 90hp Merc charging question

A rectifier rectifies alternating voltage (AC) into direct voltage (DC). House power is AC. Batteries supply DC.

The alternator on your OB supplies AC. Recitfiers are necessary to condition it so that the battery can accept it.

Regulators look at how fast and how far the rectified alternator output gets crammed into the battery. They monitor current (amperage) and voltage (DC) so that the battery doesn't charge too fast nor charge too long (to too high a voltage). Among other things, this keeps the water in your battery and prevents it from boiling out.

Mark

 

[jpollman]

Re: 1990 90hp Merc charging question

I'm assuming that you saw my post concerning the same problem. At this point I think that I may have solved it but won't know until the parts come in and I can get it reassembled.

Briefly I'll say that I had an overcharging problem also and was getting as much as 16.8V out of the regulator. I tried installing a new CDI regulator and that did nothing. I then discovered that recently (before I bought the boat) someone had installed a new CDI 9amp stator. I tried three different batteries and the only one that worked seemed to be a big Delco Voyager deep cycle. With that I could only get 13.5V out of it. But after testing a couple more times I found that the voltage creeped up even on that battery.

Eventually I found a Merc dealer in my area that was very helpful and I think he's solved the problem. I gave him the S/N of the motor, the part number of my flywheel and regulator. He did some looking and found some service bulletins. Apparently in the early 90's Merc had a LOT of trouble with their "black stators". I guess they redesigned them and made them a "red stator kit". This was to fix the problem. I guess in the "kit" there is a stator and a module that plugs in between the stator and the regulator.

Anyway, I've ordered a 16A Red Stator kit and a new regulator/rectifier. The parts should be in today or tomorrow. Unfortunately it's an hour drive to go pick them up but at this point I just want this thing fixed so I can get some fishing time in while we've still got some summer left.

Oh yeah, I thought my motor was a '91 90hp Merc but by the serial number I think it's a '92 model. Either way, I think it's probably pretty much the same motor that you have. The dealer also told me that if I brought the boat with me he'd change the registration on it to my name so that if there are ever any safety recalls or issues I'll be informed by mail. Which is good because I guess that there's a fuel line/filter issue that needs to be dealt with on this particular motor.

Good luck and I'll let you know how things work when I get this new charging system installed. It should only be about an hour worth of work and she'll be ready for the water again!

John

 

[dingo99]

Re: 1990 90hp Merc charging question

Thanks for your help, I have a 3 wire rectifier, 2 yellows from the stator the third stud to the battery terminal connection. The rectifier and diodes check properly for continuity. One of the yellow stator wires has a lt gry wire that continues to the 9 pin plug( I assume it for the voltmeter) Load tested the battery this AM and found it fine . Local merc. dealer says 99.9% it is the rectifier, as this type of rectifier has a ziener tyoe diode built in which you cant check. Before I cough up the $40 for the new rectifier, does this sound like a logical comment??

 

[Texasmark]

Re: 1990 90hp Merc charging question

That light grey wire is either for running lights, or since you only found 2 yellow wires and none others, it may be used for ignition.
--------------------------

The 3 wires are yellow for ac input as I said before and the stud is apparently the + output to the battery pos. The Battery Neg connection must be through the base of the rectifier (where it mounts to the engine). You have to have a ground return somewhere; won't run without it. Might insure that the mounting hardware and surfaces are clean of corrosion and tight.

HTH

Mark
The zener diode is a gate. It is reverse biased (no current flow) until the applied voltage reaches it's breakover point, at which time it starts conducting current to maintain that breakover voltage.

It tests and will run as pretty much any other diode except for it's PIV (Peak Inverse Voltage) being matched to the circuit, rather being much higher (like a rectifier diode) which don't (aren't designed to) break down under applied voltage.

Problem with trying to check it is that it is wired up reverse to the rectifiers and unless you take it out of the circuit other things there can give you a confusing reading.

On $40, what is your time worth?

HTH