1976 merc 7.5 missfire

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capnfred

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Jan 20, 2007
Messages
10
I have an 76 merc 75 which has a missfire, if I pull the wire off the plug so it arcs to the plug it will smooth out, any ideas are appreciated. I have replaced the coils and the wires, and the plugs..... any ideas are appreciated... it starts easy, runs fine once I pull the plug wire..... thanks

Capnfred
 
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Laddies

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Sep 10, 2004
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12,218
Re: 1976 merc 7.5 missfire

It sounds like low voltage at start up, needs to be tested with a DVA to be sure but that quite common as a switch box is a on it's way out
 
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capnfred

Cadet
Joined
Jan 20, 2007
Messages
10
Re: 1976 merc 7.5 missfire

Thanks, do you know what the voltage should be on the coils coming from the switchbox....I have quite a high potential on the secondary of the coil, will arc 1.5 inches or more.......also I have read many conflicting lists as for what the correct plug and gap should be. The previous owner had H10C champions in it.... any advice there is appreciated...

Thanks

Capnfred
 
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Laddies

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Sep 10, 2004
Messages
12,218
Re: 1976 merc 7.5 missfire

Switch box output should be 150+ volts with a DVA. L78V plugs some use L77J4Cs
 
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