Simply start with points. Clean and adjust. Double check carb again. Those two are good it's a cool. Simple. I'd really have high doubts it's in the plug wire but could be. My 64 9.5 has a kill switch. Just sold a 71 6hp. No switch

double checked the plugs no fouling, removed the kill switch no change in trying to start it. Im thinking now of pulling the top to check the points. Im starting to think like Jonnytrapper now that both points corroded over the winter. But if the coils are prone to going bad I guess both could have went at the same time. I will see if I can use the few wheel pullers I have to pull the top if not will build one. Then hope to find some parts if not might have to go with Newts suggestion and pony up for a new one maybe a 4 stroke seems the old 2 cycles are going like the fur market!

might have to go with Newts suggestion and pony up for a new one maybe a 4 stroke seems the old 2 cycles are going like the fur market!

You will be glad you did.
Nothing like a new 4 stroke

With the energy transfer magneto system if just one set of points stops working neither plug will have spark.

Guys I made a terrible mistake. I guess I was sleepy the night I entered my post about your 1975 Johnson. I told you I had a 1975 Johnson with the electronic ignition. I totally lied to you, but not meaning to lie to you. My Johnson is a 1985 model. I knew that it was, but for some ding dong reason I told you it was a 1975 model year. Sorry about that. If you have not figured out what your problem is I will think about what can and will go wrong on that model year. I commercial fished for years and always worked on my out boards to keep them running. Only a few things can be wrong with that model and they are pretty easy to figure out. Good chance you have a short some where in your system. Your spark advance plate might be getting a worn bearing around you crankshaft. Have you pulled off your flywheel yet? If you have not, then you need to and start seeing if anything is loose or wobbling to much. Then check your points to make sure they are opening and closing correctly. Also make sure the little cam that drives the points is working. That is a couple things for starters. These things may have already been mentioned by someone else. I didn't read any of the other post past my big screw up.

id start with easiest first-new plugs, especially if its bee sitting
next clean your points, I use either fine sand paper or a fingernail file
then check your wiring for rubbed(shorted) wires
after that could be condensors.
if you don't have much experience id recommend getting a manual. these engines are pretty simple and easy to work on

I have a 77 15 hp and had to change the kill switch several yearsw ago. Still runes great. I use the gas additive at every fill up also.....jk

Ok pulled the fly wheel today cleaned up the flywheel contacts and checked for loose wires or cracks all the wiring looks great the points are both opening all right and according to the stamp on the flywheel the points are supposed to be gaped at .20 and I used a feeler gauge and they are about .18 and one slightly out of alignment but Im not thinking bad enough not to totally fail. Not sure how to test the condenser or coils. All of the wiring looks and feels like new very playable and everything looks tight. Put in new plugs and no change. Is there a way I can test condenser or coils or magneto before buying new parts?? Also might mention the cam seems in good shape and on top dead center the points seem to open properly. Thanks for the continuing help.

I'm not sure this will help or even work but..if you can pull the wire going INTO the coil and check for spark there ...that might indicate the problem is back upstream.....or at the coil. Was there an exciter coil or anything like that under the flywheel ?

I'm pretty sure with this setup if a condenser was bad you have no spark at only that cylinder. Since you have no spark on both cylinder your likely going to find a bad set of points, bad driver coil or shorted kill switch.

Did you unhook the kill switch and try it? Both the points and coils can be tested with an ohm meter. To test the points unhook the wires and check resistance. I'm the closed position it should read pretty low like less than .5 ohms. You'll have to look around for the specs for the driver coil.

Condensers can fail without warning, I have read you can check them with ohm meter. They have an Internal spring or contacts of sort I believe. They short out and fail.

A condenser is just a capacitor. It stores energy and in this application is used as a dampener to prevent arching when the points open.

They do fail but then he would more than likely have spark at 1 cylinder.

Well back at it tomorrow got on line just to look for parts and not finding much but will keep working at it to good of motor to just chuck. I guess everything gets to the point where they quit making parts though 1974 heck thats way younger than me! I really do appreciate all the help. Will let you know what I finally figure out. Seems like the figuring out the problem with electrical is harder most times than the fix!

I did unhook the kill switch right after testing for spark that was my first guess since no spark to either plug but no luck.

Just ordered up some new points cheapest part also found all the components I might need at a great source CDI marine electronics easy to use site just pop in the model number and type of engine pull up a schematic which list all the parts and numbers for original parts and after market. All the parts seemed very reasonable price wise except a kill or short switch $65!! I did check that 3 times and don't think its the problem and if I ever did need one $5 single pole switch will suffice. They also have all the manuals for boat motors, how to videos and a forum for repair questions so will try that for ideas. Thanks again for the help will let you know what the problem was.

Well and the winner is! it turned out to be the driver coil that works with the magneto and supplies the juice into both coils. Anyway I really appreciated all the help and found a great and easy site to order parts on line for the older motors and also new. The site is CDI marine and electric parts. Time to go fishing!

Glad to hear it. It's always nice when people come back and let everyone know what the problem actually was.