Re: 70 HP Johnson 1978
Those numbers arent bad, the middle cylinder seems a little low, try a decarb and see if that evens things out a little. Invest in a can of seafoam, in a portable tank, mix 3/4 gallons of premix gas, an 3/4 can of seafoam, (assuming you don't have the vro connected). Put the remaining seafoam in a spray bottle, run the motor up to temperture, remove the plugs, one at a time, spray some seafoam into each cylinder and replace plug. Let it sit 15 minutes, remove the air silencer from the carb while waiting, restart motor, and spray seafoam into each carb, until it start to stall. Repeat until the seafoam is gone. Run out the remaining gas. It will smoke like it is on fire, and drip goo on the ground. Replace the plugs with new ones, and then do the compression check again. This procedure burns the carbon out of the motor and been known to free up rings and increase compression. If you cant get the jet out, you could always try some small wire then aerosol cleaner or compressed air to blast it out. The high speed jet is about half way up the side, in what looks like a long tube running the length of the carb. And finally like I said, a manual would pay for itself 100 times over.
