Running on 1 Cylinder

[johnrolf]

I have a 1972 20hp mercury pull start. The motor will only run on 1 cylinder at a time. The left coil is wired to the top cylinder and the right coil to the bottom cylinder. The top cylinder works fine. The bottom cylinder will also work if I connect it to the left coil. But only one cylinder will run at a time. The right coil is producing enough spark to shock me, so I think it's good...? I know that the problem is NOT the spark plug wires or plugs. What could the problem be?

 

[emckelvy]

Re: Running on 1 Cylinder

Could be a number of things, culminating in a bad stator assy.<br /><br />But before you condemn the stator, pull the flywheel and clean/regap the points to .020"<br /><br />Also replace the white insulators where the wires come thru from the outside, to the points. These insulating blocks have a bad habit of shorting to ground and killing the spark.<br /><br />Many stators have been diagnosed as bad when all along the insulators were shot.<br /><br />If you don't get a spark in #2 after doing that, most like the stator is shot and needs replacing.<br /><br />Suggest eBay or finding a used one at various outboard parts sites, as a new one is quite $$pendy.<br /><br />HTH and Good Luck.........ed