New Coil, No Spark

[litroc]

I have a 19 ft. Searay with 165 hp Mercruiser.(late '70s)
I put in new plugs, points, rotor, cap and tuned it up like I do every year.
The gas is fresh, the battery is new, the starter turns real good.
I took it out on the lake and it started and ran good for 10 minutes at WOT. Then it just stopped dead in the water and would not start. I checked for spark on the plugs and got nothing. I checked for spark on the high voltage terminal and got nuthing.
I replaced with a new coil and I still got no spark. I have 4.3 - 4.7 volts on the coil terminals when the key is on. I get 7.5 - 10.2 when the engine is cranking. But I get 'No Spark'. Any suggestions or help would be greatly appreciated.

Thank You

 

[bruceb58]

Re: New Coil, No Spark

As a test, run a jumper wire from your battery to the coil and see if it will start. if it starts, you need to track down the voltage supply to your coil.

There are many places for a bad connection.

This is the path

1) Starter solenoid where battery connects
2) Engine connector toward your dash
3) Fuse panel up to your ignition switch
4) Back to your engine connector.
5) Ballast resistor or resistor wire.
6) Finally wire going to the coil.

With the points open, you should measure 12V at the coil. With the points closed, down near 7V.

 

[JustJason]

Re: New Coil, No Spark

pull the condensor out and test it with a DMM. Put your meter on OHMS and attach to the condsenor. If the resistance gradually builds up to infinity the condesor is good. If it does anyting else it is bad.

 

[litroc]

Re: New Coil, No Spark

Thanks guys, I went through all the steps you both wrote. It was my condensor, that really surprised me because it was a brand new condensor, I bought 2 days ago and put it in. I did not expect a new condensor to be bad. Anyways, thanks again guys for your help. I hope I can return the favor some day.
P.S. This a great site!

 

[JustJason]

Re: New Coil, No Spark

I hope I can return the favor some day.

If you can't pay it back, try to pay it foward.

BTW, I've had many a dud part or a part that goes dud within a day that was new in a box. It's enough to drive you crazy sometimes.

 

[bruceb58]

Re: New Coil, No Spark

I have had condensors go bad as well but was throwing me off were the voltage measurements. Please explain how you were measuring voltage. Were you measuring from positive side of the coil to ground or across the coil terminals. Measuring across the terminals really isn't going to tell you a whole lot other than the voltage drop of the coil.

 

[litroc]

Re: New Coil, No Spark

I was measuring across the coil. I also discovered that I don't have an external resistor. I have a resister wire going to my coil. That surprised me I had never heard of that before.

 

[bbbobbb]

Re: New Coil, No Spark

I'm getting into a problem finding my external resistor but on another boat, Were is your located at ?

 

[Bondo]

Re: New Coil, No Spark

I'm getting into a problem finding my external resistor but on another boat, Were is your located at ?

Ayuh,... So start a thread of your Own, explaining Your boat, motor, etc.,+ Your problem...