75hp Chrysler No spark in one of three cylinder

[northworm23]

Hello all.<br />New problem...actually old but just diagnosed. My 1976 75hp engine has three cylinders with the three carb setup. It has the magnapower ignition with the disributor and cdi pack. It runs very rough and won't hold a good idle. I put in new spark plugs and after a run up I checked the plugs. The bottom plug was still clean and dry. I tried another plug with the same results. What would cause just one plug not to fire?<br /><br />Thanks!<br />-Steve

 

[eurolarva]

Re: 75hp Chrysler No spark in one of three cylinder

Looking at the schematic it appears you have CD units for that ignition. Each CD unit supplies spark for two plugs. The second unit will have a spare because you only have three cylinders. I have no experience with this ignition system so you might want to try THE MARINE DOCTORfor more exact information. If the cd unit is bad you could try moving the wire over to the un used postion and see if it will fire the plug.<br /><br />Also it would not hurt to compression test this motor to verify that this is a spark plug issue and not a blown head gasket. Either a compression test or move a dirty plug to the non firing unit and see if it comes out clean after you run it awhile.