Logo
FULL SITE MENU

1986 omc 2.5 Coil overheats engine quits

G

guitarguy

New member
new alt, new carb, new fuel pump,points. cond. rotor, runs great until about 30-40 minutes then dies. Moved coil about an inch away from the block, now it runs for 1 hr and 20 minutes and quits. Coil gets real hot. Help!
 
coil should be warm but not "hot"...you should be able to touch it with no problem. excess heat indicates too much current flowing thru the primary.are the points still in or did the distributor get a conversion kit?
 
makomark said:
coil should be warm but not "hot"...you should be able to touch it with no problem. excess heat indicates too much current flowing thru the primary.are the points still in or did the distributor get a conversion kit?
Click to expand...

Still got points..... and thx so much for replying. :) Coil gets quite hot to the touch.
 
makomark said:
what's the voltage between the + terminal of the coil and ground when the engine is running?
Click to expand...

Voltage is 11.20ish... Let me give some history. When the old alt. went it made a popping sound. After installing the new alt. the new batt. would not hold a charge. The batt. tested for a dead cell. Thank you Mr. Alt. Now the only problem is the coil overheating and at this point I am wondering if the alt blew the ballast wire and were and how do I get a new one? There is nothing like a little fun on the high seas. :)
 
With a voltage that high, I'd suspect there's a mismatch between the ballast wire and the coil allowing too much current (thus the heat)....see if the coil has any part number on it or, better yet, specifies the required ballast resistor (usually in ohms). You can also measure the voltage drop across the "ballast wire"....FWIW, I've never seen a ballast wire fail in a low resistance mode....they usually open (or a bad crimp corrodes). It may be easier just to add an old style resistor.....another option would be to get a breakerless conversion (replace the points) - many, but not all, direct you to remove any ballast resistor or wire.....
 
makomark said:
With a voltage that high, I'd suspect there's a mismatch between the ballast wire and the coil allowing too much current (thus the heat)....see if the coil has any part number on it or, better yet, specifies the required ballast resistor (usually in ohms). You can also measure the voltage drop across the "ballast wire"....FWIW, I've never seen a ballast wire fail in a low resistance mode....they usually open (or a bad crimp corrodes). It may be easier just to add an old style resistor.....another option would be to get a breakerless conversion (replace the points) - many, but not all, direct you to remove any ballast resistor or wire.....
Click to expand...
One of the manuals says that a sympton of a defective ballast resistor wire is that the engine will shut down when you let the starter key return to the on position. That is not a problem here. I would like to thank you for your input, just not sure what to do at this point. :)
 
the manual describes the "open" failure mode of the wire.....I'd say you have the wrong coil and the wire is fine or you have the correct coil and the wire is wrong....have you measured its resistance (measuring the voltage drop across the wire will give you the same info)?

Either way, the time to shutdown will continue to decrease if you don't figure it out...eventually, the coil will fail.
 
makomark said:
the manual describes the "open" failure mode of the wire.....I'd say you have the wrong coil and the wire is fine or you have the correct coil and the wire is wrong....have you measured its resistance (measuring the voltage drop across the wire will give you the same info)?

Either way, the time to shutdown will continue to decrease if you don't figure it out...eventually, the coil will fail.
Click to expand...

The ballast resistor wire is as far as I can tell is original. It measures 2.5 ohms. The coil measures 9.8v w/. eng not running. 11.20v w/ eng. running. Batt is 12.9v not running 14.6 running. Thats all the news thats fit to print, film at eleven. :) Thx again for all your help.
 
I am now suspecting that the mounting bracket is transfering heat from the cyl head to the coil. Time to reconfigure the mounting bracket.
 
Back
Top