Re: 1972 Merc. 4HP MN.

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20mercman

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Replies: 613
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#79310

John, It is Interesting that I just completed a full restoration of a 1974 4hp this week. One thing I would check is the coil. I know you say it is producing spark, but I have found these style coils start to crack, will fire in open air, but will jump to the cindered iron core when under compression. Your insulator in the primary side of the ignition circuit should be OK, or it wouldn’t have spark in open air. These systems create a high voltage in the primary circuit that goes to ground when the points close. This allows the capacitor to discharge through the primary windings of the coil to ground. This is why they are called "Maker points" vs. "Breaker Points" These "make" the circuit when they close. This causes high voltage on the points, and they will typically have a significant burned look. This is normal and should not be a reason to replace them. Another issue you may have, is a flooded condition. If you have a failure of your fuel pump diaphragm or the fuel pump is assembled wrong, the fuel will run through the pulse line directly to the crank case, and cause a flooded condition. Is your test tank full of unburned fuel? Pull the pulse line off the fuel pump or the case end, and see if it has fuel in it. This will cause a no start condition as the motor will be severely flooded.

Please keep us posted.
Thanks!

Steven A. Carlson

P.S. (Valerie is doing OK)