I just got a little run about that has a 1975 Johnson outboard. It supposedely ran when it was put up. Motor spins over, has seemingly good compression. The symptoms are no spark while cranking over when spark plugs are screwed into the heads[ motor spins over at normal speed] but if i remove the plugs from the head and ground them I get good blue spark. I put new plugs and battery in as a precaution. I also tried unplugging the control box harness and jumping the solonoid,same results. I also tried grounding the base of the plugs to a different grounding point thinking the heads might possibly have weak grounding[ Yeah I know but I was out of ideas] Any ideas , Thanks

Are you sure it's getting fuel?

(If you've got a spark when they're out, not really sure why you wouldn't have spark when they're in.)

make sure that you have fuel in the BOWLs, older premix engines somtimes the fuel evaporates and just leaves oil in the bowl. Pull the plugs on the bowls and pump the primer ball on see if you get fuel flowwing

I agree with the other responses. Make sure you are getting fuel. If your plugs are wet with fuel and it is still not firing, you have bad fuel. How long has it been sitting?

Drain the carbs (there is a bowl drain) connect fresh gas and try.
If the motor has been sitting for a couple of years, pull the carbs and clean them. A plugged jet can put a cylinder in a lean condition and cause damage.

There is fuel in the bowl. I am using a in line spark tester to diagnose the no spark condition. will this type not work on a CDI? I tested the devise and it does in fact work.any other ideas, I also lifted the black/yellow grounding wire, same result. weird right!

These battery CD ignition need at least 9.5 volts to fire the pulse pack. Check all the connections and grounds. Make sure your battery is fully charged. A starter that is dragging will also cause no spark with the plugs in.

You hit the nail on the head!!! Pulled the flywheel just to check..ok ,new battery fully charged,,, while cranking and all plugs out ,plenty of spark. still cranking I held the plug over the plug hole,rpm's dropped SLIGHTLY and spark went away. I then put my battery charger on boost installed plugs ,Engine popped right off. Checked starter and battery leads,although cables looked good they had way high resistance. good call mwillis

wasn't 75 mag cd..?
post your model number or a photo of the powerhead from the RHS
69 70 71 72 all had Motorola batt cd and I thought all models changed to mag cd for 73....or am I loosing some grey matter..had to happen one day

while your there check to see if the 2 (charge ) coils you can see on the front and back of the stator ( under the flywheel with it still on) have not dripped their potting glue down onto the powerhead... this means they are on their way out and can make the difference when your cranking speed drops a little.
Sensor coil voltage gives the same sympton.
The quick check is with a peak voltmeter..