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Erratic voltage readings

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chonka

Member
Good morning all,

I have a 1967 Mercury 950 SS with serial number: 2100114 and it is mounted on a 1965 Lone-star aluminum hull. I am getting some erratic voltage readings from my charging system at the battery and at the engine. I am using digital multi-meters for the testing.

First off at the battery my meter reads 12.5 vdc before start up. After start up the meter readings jumps around and then the meter shuts down (It just turns off. I'm assuming this is a safety feature on the meter). I switched to a Kliein Tools meter(MM2000). I hook the meter to the battery in volts DC mode, start the engine and the meter readings start to jump around and then switches to AC mode while still jumping around (not going above 4 volts AC)(I'm also assuming that it has an automatic input feature (AC to DC)). I also get erratic readings while the engine is running and I touch only one lead of my meter (in volts DC) to the chassis of the engine. The other lead of the meter is dangling in the air.

At this point I disconnected the stator from the rectifier and restart the engine. I now get 5 volts from each of the yellow leads of the stator to chassis ground and 19 volts AC across the two yellow leads. I still get the erratic reading when I touch one lead of the meter to the chassis.

This has lead me to believe that I have AC voltage leaking into the ground of the chassis or a loose connection. I removed the fly wheel and checked continuity from the chassis ground to each of the output wires to find none, so its not grounding to the chassis. I did find where the yellow leads connect to the first two coils on the stator to be a bit corroded and the timing belt to be well dry rotted ( i do not feel the belt had anything to do with my problem, but needs to be replaced).

This outboard seems to have the older rectifier(32177A 2) with shorting clipper. I am not sure if this is the right one, I thought it should have the 78614A rectifier.

I am looking to replace the stator, if I can find one, along with the rectifier and belt. At the very least I will replace the rectifier and belt and reconnect/clean the corrosion from the two yellow leads and re-insulate the wires.

Any help is appreciated with this issue. Also, I know the stators are obsolete, but does anyone know were to get one, or a compatible replacement?

Thank you,

Chonka
 
kimcrwbr1,

Thank you for your speedy response. Here are a few clarification points and a few more questions.

I put a new internal and external wiring harness in about 6 months ago. There is only a few wires that didn't get replaced i.e. the choke solenoid , the wire from the rectifier to control box and wires to coil. I will go back over them again and check for resistance and continuity to chassis. This boat and motor combo is new to each other. I installed the outboard at the same time the harnesses were installed. The outboard runs great and idles really smooth.

I will also check resistant from the stator wires ends back to the coils on the stator again and post my findings.

So with your information and suggestions I have several more questions:

-If I confirm the stator is good and replace the rectifier/regulator with the newer style, I do not need the clipper, correct? It is my understanding that the clipper was used on non SS models and was to protect the control box from shorting.

-The rectifier by CDI electronics that you posted a link to on Ebay is for a Johnson/evinrude, will this work on a Mercury?

-If the stator is bad or the wires coming out of it are bad what are my options? I have not found a good replacement. Is there some way I can retrofit a stator from a new model on to it?

I use my boat as a dive boat in area lakes. Its a work-boat and by no means a "classic that needs to stay all original." If I can retro some new technology that is a little more dependable, I'm all for it. With that said, A new boat and motor would be ideal, but right now it's not in the cards.

I again want to say: I appreciate all the help I can get. Information about old mechanics is dying out with the newer generations of boaters. I have experienced the same thing with older Harleys. Most of these new riders don't want to learn how there bikes work.

Thank you again,

Chonka
 
Thank you,

This gives me a starting point. I am going to do some more testing tomorrow morning. I will report back after that.

Chonka
 
You stated: "At this point I disconnected the stator from the rectifier and restart the engine. I now get 5 volts from each of the yellow leads of the stator to chassis ground and 19 volts AC across the two yellow leads. I still get the erratic reading when I touch one lead of the meter to the chassis. "

I don't know much about those old Merc's. I've owned one back in the early 80's and then sold the rig. However, the 19 volts AC off the stator sounds about right. The erratic readings are likely from the rectifier/regulator. And if the only thing the rectifier/regulator is doing is charging the 12 V DC battery, then it seems to me that just about any marine rectifier/regulator that converts the 19 volts AC to, say, 13.5 volts DC will do the trick. Heck, many years ago I hooked up a rectifier/regulator from an old Kohler engine to a Johnson 50 and it worked fine. Ugly as hell, but it worked.

BTW - many digital multimeters have a difficult time accurately reading the fast switching AC sine curve produced by a small engine stator. I learned that the hard way.
 
I did a little more testing this morning and here are my findings:


Rectifier(Bench test):

-From input post A (one of the input terminals) to rectifier output: 6.78 M ohm
Reverse leads of meter: .671 M ohm
-From input post B (the other input terminal) to rectifier output: 3.226 M ohm
Reverse leads of meter: .374 M ohm
-Between input post A & B: 4.16 M ohm

I originally stated, in my first post, that I was not getting continuity from the stator output wire back to my chassis, but when bench testing I was getting some. Here are my findings:

Stator (Bench test):

-Yellow output 1 to stator mounting screw hole: .521 M ohm
-Yellow output 2 to stator mounting screw hole: .511 M ohm
-Between the two yellow outputs: .3 ohm

One of the problems I am have is my two reference books have conflicting information. I am not sure what to go by. I have included a few pictures of the relevant pages. The Mercury service manual does not even list the right stator for my year.
The rectifier seems bad. It should not have continuity in both directions (through the diodes). I checked for grounding in the rest of the wiring and found none. I am still questioning if the stator is good. I will be contacting CDI to see if the stator 174-4793 has the same bolt pattern. I am contemplating replacing both if I cannot determine if the stator is bad or not.
Thank you both for the input; I am at ease about the rectifier I just need to figure out the stator now.
Thank you,
chonka
 
I failed to mention what started the whole thing. It was me trying to hook up a new tachometer. I did the research, bought a FARIA THC622A. Put the tach on 12 pole and hooked in to the output side of the rectifier, nothing. Put it on the tach wire of the control box, nothing. that is when I started tracing voltages.
 
I have not found any markings on the stator, but it is a 12 pole and looks just like the ones in the service manual. It has long leads that are hard wire, not braided. I replaced both internal and external harnesses with CDI harnesses. Both harnesses had a orange and a brown wire that wasn't used. I used the brown for the tach and the orange for a "key on" to the hour meter.
 
Ok, I am eating a little crow here. The second reply to my topic was from kimcrwbr1, he suggested I go through every wire. I thought I did. Evidently I did not test the wires well enough in the distributor. the following is what I just posted to another forum:


Hello all,
I have a 1967 Mercury 950 SS with Serial # 2100114. I have been trying to track down an electrical issue on this outboard and found that the two wires coming from the distributor (points) were bad (Bad as in: internal corrosion, shorting, cracked insulation and very high resistance). I installed a new engine wire harness last year and have checked every other wire that was not replaced. I have tested the stator and it checks out, OK. The outboard originally had the older orange rectifier; I switched it out for the newer diamond shaped one. The old one tested bad and now the new one tests bad. I am assuming it is from my shorted out wires. It must have blown one of the diodes. I already have a new rectifier (new style) and will install it when I replace the wires from the points.
Know here is one of my dilemmas. I was combing the internet today and came across a post on another forum and this is one of the replies in the topic:

“There were three 950s (and 1100s)...

Early 66 ones had the original dual point distributors with side electrode and dual coils. These also had thicker rings. The middle SS models made in 66 had dual point distributors that fired an electronic ignition and the 67 SS models had full electronic ignition. The 66 SS models used the 1/16" rings with small piston pins and the older style rods. The 67 models used the newer larger rods and pistons with larger pins.

The distributor head from a 67 will, I believe, mount on the earlier models to give a easy path to electronic ignition. I'm not sure however with the tang on the drive shaft and the rotor shaft, it might even run backwards...

There's a picture of my 66 1100SS on the site somewhere. It has silver/red decals and a flame on the lower cowling trim horse shoe.

I always thought the 950 was rated at 95hp instead to make the 110hp 1100 look more attractive. That's probably showing my bias against marketing people. Just as the 1250 looked much more attractive vs the 1000 instead of the 1100... Kinda like $19.95 seems like a lot less than $20.00?!?”

This reply was written by username CrayzKirk. I suspected something like this went all, but was not sure. It all makes more sense to me about the identification of my outboard. Mine falls in the middle category, so I have a dual point set up with single ignition coil. My question is: will the solid state trigger coil fit my distributor (I would change the rotor also) and where do the three wires hook up. As of right now the dual points have one wire each that connect to a single post of the switch box(left side of box as if you are driving the boat). The condenser is also connected to the same post. The newer solid state trigger coil has three wires from it (brown, Black and red, (I think)) that connects to the switch box using three separate terminals. Would I have to change out the switch box? Or is there a way to hook up the trigger coil to the older switch box. Cost is also a concern; if I have to switch out the switch box I will stay with points.
I will upload some pictures of my set up.

Thank you,
Matt
 
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