1982 Mercruiser MCM 140 No Spark

I recently purchased an old 82 Rinkerbuilt that has an 4cyl Mercruiser MCM 140 in it. The motor will turn over but there is no spark. I have replaced the ignition switch, coil, points, condenser, rotor, plug wires, and spark plugs. The points have been set to the specs on the side of engine block. When I try to start it I get a current through the wire that goes from the coil to the distributor cap but I get nothing through the plug wires. The cap looks brand new so I have not replaced it and when I jump a current from center of the distributor cap to one of the posts I get a good voltage reading. I cannot figure out what else could be causing no spark. Please help...

if you claim you see voltage ,then your reading 30,000-60,000 volts so you have spark?????????

With the key on the "on" position you must have 12v at the + side of the coil. putting your meter on the neg side of the coil and a good ground, cranking the motor must make the needle move. that tells you the points are opening and closing to produce spark

Is the carbon 'finger' in the cap still there, and is it touching the rotor?

Jeff

After a few more tests it is apparent that it is not producing anywhere close 30,000 to 60,000 volts. The voltage is there it just seems that it is not strong enough to produce a spark.

Disconnect the tachometer from the neg side of the coil. recheck

Also you may have a wiring issue.
The wire that feeds the coil + is a resistance wire and it is about 3 feet long.

it is taped in the wiring harness on the engine.

I would do this as a test only.

Schematic shows three wires possibly to coil.

1. wire from starter solenoid (Cranking 12 volts to coil)
2. resistance wire (ignition on 12 volts while running to coil)
3. possible lead to alt but most likely not there

remove the wire (s) that goes to the coil + and tape it/them off.

The + 12 volts wire it may be purple/yellow or tan in color and it comes from the starter solenoid I terminal??
The other will be the resistance wire remove that also and tape off

Then run a wire directly from the battery + to the coil +.

Recheck the spark only. if you run it this way you will burn out the coil (no resistance, which by the way should be ~ 2 Ohms for the 3 ft of wire)

If it looks good then you most likely have bad wiring. Check the wire from the starter solenoid to coil and connections for cranking spark.

check resistance wiring for running spark


Oh and you will be lucky to get 30,000 volts no matter what

When I try to start it I get a current through the wire that goes from the coil to the distributor cap but I get nothing through the plug wires. The cap looks brand new so I have not replaced it and when I jump a current from center of the distributor cap to one of the posts I get a good voltage reading. I cannot figure out what else could be causing no spark. Please help...

With the key "on" check for 12v at the + side of the coil. Using volts, Put your meter one lead on the neg post of the coil and the other lead to a good ground. report the results

..."Is the carbon 'finger' in the cap still there, and is it touching the rotor?"

Hate to have to repeat myself!

Jeff

Had the same problem with my old rinkerbuilt 470. The signal to the points was getting lost to the tachometer. Disconnect tack.