75 mercury only fires in 2 cylinders

mjg

Cadet
Joined
Aug 5, 2003
Messages
9
My mercury 2 stroke only seems to be sparking on cylinders 1 and 4. the spark plugs on 2 and 3 seem to be dead. i have checked the spark plugs and HT leads on all 4 cylinders and they are ok. it has 4 seperate coils which i have yet to swap around. does anyone know of any obviuos solution to this problem or is it a case of just trial and error. any suggestions will be greatfully received. the engine is from the 70's i think with twin carbs. <br /> many thanks in advance.
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: 75 mercury only fires in 2 cylinders

Unless you have a DVA meter, you will have to swap wires out and see if what works and what does not work.<br /><br />You can swap all the wires. Stator wires to Stator wires.<br /><br />Trigger wires to Trigger wires.<br /><br />You will not hurt anything by doing this provided you are suppling a place for the ign coils to ground through the sparkies.<br /><br />With the symptems that you are reporting...it could be any of the electronics.<br /><br />TMD
 

mjg

Cadet
Joined
Aug 5, 2003
Messages
9
Re: 75 mercury only fires in 2 cylinders

Thanx marine doctor, i have tested the trigger wires with a dvm and they are ok, the only thing i didnt check was the trigger voltages which i will do later. if they are ok then all thats left is the 2 coils. i guess my theory about only starting on 2 cylinders is incorrect. thanks for your responce.
 
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