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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 1976 Mercruiser 165 IO on a 23' Allmand My ignition

Customer Question

I have a 1976 Mercruiser 165 IO on a 23' Allmand
My ignition has failed twice now after replacing coil, points, condenser, plugs
After about and hour of running, especially at idle, it shuts down and will not restart
No fire to'points, coil hot
Replaced coil with aftermarket at 2.25 - 2.5 ohms resistance
What do,I do to cure this annoying and expensive towing back home !?
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.

What coil are you using? Internal or external resistor?

Customer: replied 1 year ago.
Expert:  Jeff G. replied 1 year ago.

Check the actual voltage going into the coil when the engine is running. The coil should get warm but not hot.

Post the voltage.

Customer: replied 1 year ago.
Points have no spark
Have power to points so will not start
Customer: replied 1 year ago.
no SPARK at points
Expert:  Jeff G. replied 1 year ago.

Remove the high tension lead from the coil to the dist, hold it near a good ground, crank, what do you get?

Do you have a ohm meter to check the points? With the points open, ignition on, bridge the points with a screwdriver, do you get a small spark?

Expert:  Jeff G. replied 1 year ago.

Did you check the voltage to the coil + terminal?

Customer: replied 1 year ago.
I have power to the points from the HV wire but am getting a very weak spark at points ( .014 gap )
Is this a special wire ?, I replaced it with a larger gauge as it was suspect of shorting out
Tried several times to start, nothing
Also put in a new capacitor/condenser
Since the new coil was very hot when it shut down the last time out and would nor restart, even after cooling, might it be shot now ? What causes a coil to overheat anyway ?
Expert:  Jeff G. replied 1 year ago.

The coil could be bad now. The coil takes the 12 volts and increases it to 25,000+ volts. When it steps up the voltage it creates heat, so coils can get hot. If the key is left on with the points closed you will not only kill the battery but can also ruin the coil. If other components in the ignition system are substandard or not working correctly then the coil can't release the voltage and overheats.

As for your problem you need to make sure the voltage is not over 12 volts. If the voltage regulator is bad and putting out too much voltage the coil will go bad. So that's why I need the voltage going to the coil both at rest and while running.

If you hold the high tension wire, the fat one from the center of the coil to the distributor next to ground do you get spark?

Customer: replied 1 year ago.
I am getting spark from coil wire to ground when cranking, weak when testing a plug with them out and grounding one
Tried to start after testing, no go
Is the lead wire a special resistance one. ?
Also, what ohm resistance coiled is needed ?
Expert:  Jeff G. replied 1 year ago.

So the problem is the distributor. Check for clean terminals in the distributor cap. Are your spark plugs clean, not black and no build up of carbon. Check the surfaces of the points, are they smooth or pitted? If pitted use a fine file or sandpaper to clean them. If transfer of metal, then replace the condenser.

Your coil should be fine, it is firing.

Customer: replied 1 year ago.
All above has been done
Still no starting
Customer: replied 1 year ago.
All new parts
Expert:  Jeff G. replied 1 year ago.

If you have spark, the ignition is working. Have you checked the timing? Spray a little starting fluid down the carb, what happens?

If you have spark at the coil or spark plug it should work. Try this, take a new length of wire and run it to the + on the coil directly to the battery. Crank the engine, what is the result?

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