Burnt Points

[FISHERMAN1]

I Have A 1986 Mercruiser 3.0 Liter Io
My Problem Is That After A Complete Tuneup This Spring I Have Burnt Up 2 Sets Of Points
They Are Geting So Hot That The Metel Is Turning Purple And They Are Burning Hole Thru Contact Area
I Have Checked Voltage To Coil And It Is Around 10 Volts After Passing Thru Ballast Resitor
Any Ideals What Could Be Causing This

[TerryKing]

There are basically 3 components involved:


Ballast Resistor
Coil
Condenser


One or more of these is probably bad. More likely condenser or ballast resistor if the engine runs...

Measure the ballast resistor resistance with a good meter, compare to a new one...??

[Frosty]

A set of points are the same for ballast resistor system or without. In other words the points will handle 13.8 volts without damage.

However they wont handle continuous arcing from a high current.

A damaged coil would cause a high current draw.

[FISHERMAN1]

I Did Notice That The Coil Was Very Hot
But The Problem Seems To Have Started After The Tuneup
Plugs , Wires, Points ,condenser, Rotor Button, Dist Cap
A Mechnic Friend Told Me That He Had Heard Of Bad Rotor Buttons
Jumping Spark Back To The Points Which Cooks Them Very Quickly

[alan white]

It sounds like a bad condenser. If you haven't replaced the condenser you installed with a new one yet, take the old one and reinstall it. The circuit is simple. When the points ground the primary coil the condenser prevents the points from burning. A bad rotor button would probably only cause misfiring.
Also make sure the condenser is well grounded. The condenser, I think, is where the problem will be found.

Alan

[TerryKing]

I Did Notice That The Coil Was Very Hot(snip)...

Something is wrong here (But, you knew that :-))

My votes: Either the Coil has shorted turns, or the ballast resistor is bad.

You said 10 volts on the coil; that's a lot; usually more like 6 after the resistor. Typical resistor is 1.0 to 1.5 ohms as I recall..

Make sure you tell us what you find out!

[Frosty]

Did you check the ballast resister off the coil or on.

10 V is fine.

[FISHERMAN1]

I Took Everyones Advice And Changed The Coil, Points, Rotor Button, Cap Ballast Reistor And Condenser
Took It For A Run This Weekend And After Getting Home Removed Points To Inspect Them They Look Good After Running About 2 Hours On Them

[TerryKing]

(snip)...Removed Points To Inspect Them They Look Good After Running About 2 Hours On Them

As much as we'd like you to reinstall each part one at a time, as an experiment to prove exactly what happened, it's much more important to be out there on the water :!: