Need Help w/mecruiser 2.5 spark issue

I've been going round and round with test light and multi-meter trying to figure this out.

I have a Mercruiser 2.5 installed in a Glasstream 170 Malibu with Alpha 1 sterndrive. I am getting no spark to the plugs.

I have purchased and fully charged a good marine battery and installed a new starter ( old one was froze up ) carefully replaced corroded cable ends and connectors and reconnected them one at a time in the right places so I have a good electrical connection where it's needed. When I turn the ignition to the on position with shifter in neutral position, I have spark at the coil on both positive and negative connections. I have spark at the points, the distributor rotates and points open and close. The cap is not cracked nor is the rotor damaged. The point gap is correct. Yet I have nothing going to the plugs. I have changed coil wire to distributor cap with same results. I have even replaced the coil with two other known good ones ( tested all three with multimeter). I have checked wiring for breaks, none, bad connections, none, and juice and all seems to be in order. What am I missing? Why is there no spark to the plugs ( gaps are correct ) ? Any ideas?

Re: Need Help w/mecruiser 2.5 spark issue

Did you check the coil wire? The one from the coil to the center of the distributor cap?

Not sure you really know how to check for spark from the coil.

I have spark at the coil on both positive and negative connections.

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That is not how spark is checked. Remove the big coil wire from the center of the distributor cap, hold it about 1/2" from a clean ground (not painted or rusty) and see if you have a bright blue snappy spark. That is how you check for spark.
On the + and - terminals the only spark you will get is if you ground a wire and scratch the other end on the terminals. But that is not what fires the plugs.

Re: Need Help w/mecruiser 2.5 spark issue

I realize that Don, my apologies for not fully explaining how I checked my coils. I used an ohm meter to check that I had the proper resistances .075 - .081 at the terminals and 10k at the center of the coil.

I did use a different wire from coil to distributor and got the same result.

When checking center coil wire for spark when cranking, there is no spark.

I'm pretty good with motors and can usually get things running quickly or at least figure out what is wrong; but this has got me stumped. Is there something, some switch or component that could be grounding out the coil preventing spark? I'm not all that familiar with this motor as it's the first Mercruiser 2.5 I have dealt with.

Thanks for your help.

Re: Need Help w/mecruiser 2.5 spark issue

While cranking the engine, the ballast resistor in the feed to the coil is bypassed so the coil gets full 12 volts. When the engine starts and you release the key the coil voltage drops to about 9 volts to extend coil and point life. So what may be happening is the solenoid is not bypassing the ballast resistor and/or the ballast resistor is open or there simply is no voltage on the coil. You have done resistance testing on the coil but you have not done voltage testing to see if they have the voltage required for operation.

Re: Need Help w/mecruiser 2.5 spark issue

How do you know you have spark "at the points"? And what does that mean.

I used an ohm meter to check that I had the proper resistances .075 - .081 at the terminals and 10k at the center of the coil.

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That does NOT mean you have spark at the coil, that means you have reistance in the secondary and primary sides of the coil only.

To be quite honest, I think it needs a new set of points. The old ones are glazed over and will not actually make electrical contact. They may touch, but elecricity will not flow.

You might want to have a read at this thread. http://forums.iboats.com/showthread.php?t=335407

Re: Need Help w/mecruiser 2.5 spark issue

Issue was a bad tach wire grounding out the coil. Replaced wiring to the tach from the coil and boat is running. Thanks for the help guys.