85 hp 850 drawing power when off

[lmuss53]

I have an older 850 85 horse here to put an impeller in. The guy also brought a new battery for me to put in. I changed the impeller and went to put the battery in. When I hooked the battery up I saw a little spark from the negative cable when I hooked it up. I tested the motor and everything works fine (new impeller and starter), but the little spark kept bugging me. I took the meter and checked the flow and the motor is drawing 7 amps of current when everything is shut off and the accessories are not hooked up at all.

I called the guy and he said the previous owner told him he had a solenoid put it and then discovered the dead battery next trip.

This motor is not supposed to draw any current when the switch is off.

I'm going to post a picture and talk about how this solenoid is wired, hopefully you guys can help me get it sorted out

 

[lmuss53]

Top big yellow wire goes to starter.

Bottom red wire brings 12 volts to solenoid.

Right side red wire is from ignition switch, I'm assuming it brings 12 volts to that side of the solenoid when switch is in start position.

Left side has a wire that runs to a ground post AND a small wire bringing 12 volts from small wires coming out of the inside of the black Mercury plug. I'm thinking this is the drain right here and that wire with the 12 volts does not go on that post. I didn't think of this until after I started the thread, so I might have figured it out.

The motor has some backyard wiring on it, using parts of the old Force in the dash harness and the Mercury all in the controller harness.

I think I will unhook the left side 12 volt wire tomorrow and see what happens. If the motor starts and still charges I will cap it off and forget about it.

Nothing ever got warm, or smoked. Everything is unhooked from the battery now.

Those red wires in the foreground are user added, carrying voltage from the output side of the rectifier. I am thinking that is where the wire on the solenoid post should be.

I didn't do any of this wiring.

The new owner just bought it, but has never used it.

 

[Chris1956]

I presume the red wire on the starter solenoid is a replacement for the yellow wire from the ign key? Those extra red wires connect the rectifer to the battery? That is not standard, but should be OK,

A 7A draw is a lot. It could be the starter solenoid, the recifier or just a place where the insulation rubbed off the red wire. Put your ammeter in series with the positive battery post and positive battery cable and read the draw. Now disconnect the rectifier red cable and see if that fixes it. If not remove the red cable on the starter solenoid and see if that is it. Finally, disconnect the engine from the boat harness (round plug or quick disconnect on side of motor) and see if that fixes it.

 

[lmuss53]

There is not supposed to be a 12 volt wire on the grounded side of the solenoid is there? It is coming out of the engine harness. Funny, but the yellow wire for the solenoid was hanging in there loose. That's all a result of the blended harnesses.

 

[merc850]

Since you didn't post the year here's a diagram that shows typical wiring, the ground is - with no + leads attached; the small yellow in this case is the solenoid start wire.

 

[lmuss53]

Serial number is 4539460, so a 1975 or '76.

Thanks for the diagram,

It looks like there is no second wire on either small solenoid post.

I also think the hot wire is coming from the area of the number 3 wire on the harness. That would explain the jumpers on the makeshift wiring, since that wire should be on the rectifier, not the solenoid.

I'll double check everything and if that is the case I'll move the #3 wire and get rid of at least of these add on wires.

Thanks much guys.

 

[Chris1956]

Sometimes the wires will break inside the quick disconnect plug. I had my yellow starter solenoid wire break there.

I did some surgery and pulled the wire connector out of the plug and soldered it to a wire I added from the harness before the plug. I sealed it with silicone caulk.

Sort like cardiac bypass surgery. except with silicone and solder, vs sutures.. Maybe the PO had trouble with the yellow wire at the plug?

You have distributor ignition or 4 coil ADI ignition?

 

[lmuss53]

4 coil ADI.

I see the same breaks in the yellow wire that was laying under the hood that you talked about. Someone else already did the bypass surgery here and if it looks ok and works I am going to leave that as is.

I just have to get rid of the 7 amp leak, and I think the extra wire on the solenoid is the cause of this. This is actually a very nice, smooth running, easy starting 40 year old motor.

Thank you all for the replies, I will try to get this sorted out today and let you know what I find.

 

[merc850]

The only thing that I can think of that would draw 7 amps without starting a fire is the choke solenoid on all the time.

 

[lmuss53]

This electrical system is as big a headache as I've seen on a boat motor yet.

Is the CDI and the aluminum plate it is mounted on supposed to be grounded to the battery? It looks like it is isolated but nothing works unless I ground that plate.

The starter works and the engine runs when that big blue wire is run between the ground wire on the starter and the big ground lug on that plate. If you unhook that wire the engine won't crank, even with the solenoid connected directly to that ground wire on the starter.

The short is coming from the stator yellow wires being shorted out, with 0 resistance when probed for OHMS. This stator looks new, I hate to buy another one and just kill it with this wiring nightmare.

I guess I'll blow that wiring diagram up and double check the whole thing.

 

[lmuss53]

. .

You know I think I sorted it out, the ground running from the solenoid ground post, to the screw on the rectifier base (at about 10 o'clock) was doing the same thing as the big blue ground wire I put on.

The 12 volts was coming from the yellow stator wires having a dead short, allowing the battery current to flow from the battery back through the yellow wire to the short then down the other yellow wire to the post on the rectifier in the 9 o'clock position which goes to ground.

Now the question is, can I replace the stator and have this fixed, and is that added ground wire not to be there and going to cause issues? The original set up here had a similar wire running from the solenoid to that cdi base doing the same thing.

The ammeter in series with the battery is how I determined 7 amps.

Removing the wire from the rectifier did stop the short and lead me to the shorted stator.

 

[lmuss53]

Sorry for asking you guys to sort this out from a couple pictures. It helps sometimes to just write it down and get a set of fresh eyes. I am going to order the stator and make sure the rectifier is wired back up right and see what happens. Thanks for all the advice and especially the wiring diagram.

 

[merc850]

If you can run the motor hook a voltmeter on AC to the yellow wires and see if you get 13-16v output and as well hook up the voltmeter to the red post on the rectifier + and a ground and you should get a DC voltage 13-15v.
Here's the method for checking rectifiers

 

[lmuss53]

Again, thanks for another useful chart. I have all those Merc manuals in the PC in my shop, but once I started this thread I figured I's just stick with this..

 

[Chris1956]

One side of the battery charging coil on the stator is grounded. So if battery current gets onto the yellow wires, it will short to ground. However, battery current should not flow thru the rectifier to the stator. If it does, and it sounds like it does, the rectifer is bad. Run the rectifier test, if you have an ohmmeter, to prove the rectifier is good or bad.

Radio shack used to sell 25A full wave rectifiers which are much better than the OEM. You needed to change the ring terminals to spade terminals, and ground the - DC post to the block to wire it properly.

 

[lmuss53]

Just a follow up to say thanks one more time, the old 850 is back together, charging correctly and not drawing any power when off.

 

[GA_Boater]

Was it the rectifier?

I see that Radio Shack is going through bankruptcy for the 2nd time. I better get a couple of those rectifiers before they all disappear. The last one is working great and some cheap insurance.

 

[lmuss53]

I think it was just bad back yard wiring by whoever blended the Force factory harness and the Merc 850 harness, they had a couple extra wires on the rectifier. One of them was bringing 12 v from the solenoid and putting it on a post with one of the yellow wires from the stator. It was bleeding off at the 7 amp draw through the stator. I wired it to the diagram provided above and everything worked like it should.

 

[GA_Boater]

Oh - POOP. Prior Owner Obligatory Procedures. :smile:

Glad it's all good now.