General head gasket question

I have this 75' 9.9 HP Evinrude. Been using in a salty area for about 6-7 years.
My son had it out the for the second time this year, 14' boat loaded with teenagers (all girls too).
Stopped on an island to grab something and couldn't restart. Finally got it restarted and made it back.
My initial eval in the water was it was running on one cylinder for sure. I also though it looked like water in the gas, grey sludge on plugs instead of black.
I was guessing bad head gasket. Seems odd two things would go bad at once, but I assumed one cylinder was too water logged to fire.

So, checking out in the tank today, fired right up, but was on one cylinder for about 30 seconds then it picked right up and was firing on two again.
I verified with a timing light.
So I popped the flywheel and found one condenser wire rubbed bare against the flywheel. That explains the ignition issue.
Did I misdiagnose the water in the gas?
Is it possible to have an intermittent head gasket issue, or did a 10 minute ride on one cylinder make it look like that (grey sludge on plugs, one dry one wet)?
Also, while cleaning the plugs I was using an air compressor. A small piece hit my lip. It tasted salty for sure.
He swears it didn't get swamped or anything and it doesn't look like it did. The boat was riding pretty low in the water.

Forgot to mention compression is 68 and 70, which hasn't changed much since I bought it.

Thanks

Jim

you need a new compression gauge as no way will that run with 70 psi compression...

and grey sludge is normally water sign, it could be in the tank , only needs small amount in the bottom of the tank.

Everybody says the same thing about the compression. I am pretty sure my gauge is 10-15 psi low.
All my small engines are in the 70 psi range and the bigger ones with electric start are about 95 psi.
My 1973 65 HP (at 95 psi all three cylinders) will push a 1200 lb. boat and pull two skiers out of the water.
I hope you are right about water in the tank, but it was salty and I don't see condensation being salty.
With all the teenagers in the boat, anything could happen.

Thanks, Jim