Engine Wiring - Won't charge battery

[bucchb]

Well here are 2 pics of a powerhead I switched onto a Mercury 85hp frame.
I believe it is a late 70's /early 80's Mariner. 80hp - 4cyl.

Runs great, but probably needs a new engine wiring harness. However there is a broken wire and the battery won't charge.

Can someone tell me exactly where this wire goes and if it will fix the charging problem??

thanks
Bill

 

[Chris1956]

Re: Engine Wiring - Won't charge battery

Those pictures are of your switchbox. The motor charging system is seperate. Trace two yellow wires from under the flywheel to a black rectangular rectifier, with three connections. The flywheel magnets revolve past the stator under the flywheel providing AC current to the rectifier. The rectifier converts it to DC and sends it to the battery via the red wire.

 

[bucchb]

Re: Engine Wiring - Won't charge battery

Thanks Chris, I took 2 more pics of rectifier. From the look of the harness it might be hard to believe this motor actually runs?

It looks like there are (2 yellow) new wires from the rectifier and what looks like a (brownish) red-ish wire coming out.

I guess I need to start motor and check for 13+ volts from the red-ish to ground? If nothing rectifier is bad, and Radio Shack $3.00 25A is a good replacement?

If I do have voltage I need to run or replace a wire?

Second QUESTION: Is there any cheap way to rebuild these harnesses?? $130 is a rip off. If I could buy a connector the rest would be easy!

 

[Chris1956]

Re: Engine Wiring - Won't charge battery

Yeah, That harness looks bad. The RS Full wave rectifier (about 25A model) is a good replacement. You will need to convert the ring terminals to spade terminals to use it however, and remember that the -DC pole of the rectifier needs to be well grounded. The brown wire connects to either of the yellow stator wires and provides the tach signal on motors newer than '73 or so, which works with newer standard tachos. On the older motors, the tach signal came from the switchbox. I recommend you connect the brown wire to one of the yellow wires, unless you have a vintage tach already, since they are hard to find.

You might inquire about buying a new motor harness. I found one at surplusunlimited.com, for a good price. The harness is universal for both the dissy models and the ADI Ignition. On your motor the orange wire is the ignition killer.

 

[Chris1956]

Re: Engine Wiring - Won't charge battery

OK, I messed one think up, just a bit. You have the ADI Ignition, so the brown tach signal wire needs to be connected to one of the yellow stator wires, at the rectifier. Your switchbox won't generate the signal the old style tach's want.

 

[bucchb]

Re: Engine Wiring - Won't charge battery

Thanks again. When I put a meter on the red and ground and started the engine the meter jumped readings all over the place. I thought I would see "clipped" 14-16V pulses?

I guess this means I need to change. I may try this 1st and be real careful with the wires. This engine has been running for 29 years, so why fix if ain't broken (yet) ?
Need to be able to re-charge batteries though.

thanks again, and I'll let you know the outcome.

Bill

 

[Silvertip]

Re: Engine Wiring - Won't charge battery

Not so fast on junking the rectifier. This engine doesn't have a regulator so check the red wire from the rectifier along its path to the battery. This is typically the same terminal on the starter solenoid that the positive battery cable is connected to. If the battery is not being charged, it is not presenting a load to the charging system and voltage at the output of the rectifier will dance around and read higher voltage. You can also disconnect the leads from the rectifier and do a forward and reverse resistance check to prove if it is bad or not.

 

[bucchb]

Re: Engine Wiring - Won't charge battery

Ok, makes sense. However when I check the red terminal with the engine off, I do have battery voltage. Is this wht you mean?

I think you (or someone else) once sent me a rectifier test procedure showing resistance values and a diode checking procedure. That was a 1976 85hp with a potted rectifier.

Is there anything else you can think of?

 

[bucchb]

Re: Engine Wiring - Won't charge battery, 2nd POST

Re: Engine Wiring - Won't charge battery, 2nd POST

OK, I have not done anything on this yet. I figure I can use the boat without a tach and re-charge the batteries after each use for now.

I have run the boat and noticed that the tach is either not correct for this engine or there are major wiring issues. When I turn the key on the tach jumps to 2000 rpm and when running tach "flutters" at the 0 mark.

I will definetly change or repair the harness. When I do I would like to get charging and tach working. This post is a combination of facts for doing this all at once.

Laddies gave me this test procedure for the rectifier some time ago for my 85hp motor. I have attached.

Can anyone add anything???