73 Mercury 20hp won't start

[bjarnold1]

I have a 20hp Mercury that will not start. I have done a compression test and both cylinders are at 125lbs even, spark on both cylinders, disassembled and cleaned the carburetor. It will not start even with fuel mix sprayed directly into the carburetor throat.

 

[jbjennings]

Re: 73 Mercury 20hp won't start

If you've checked spark with an actual spark tester and it will truly easily jump a 1/4" air gap with a hot blue spark, then:

Put some fuel/oil mix into the spark plug holes and see if it will attempt to run. If it will, you sadly will probably have to check into the reed valves.
Just my opinion---I'm no mechanic.
JBJ

 

[bktheking]

Re: 73 Mercury 20hp won't start

Did you pull the flywheel and inspect the woodruff key, timing might be off. Does the motor have surface gap plugs in it?

 

[bjarnold1]

Re: 73 Mercury 20hp won't start

I checked the spark with a spark tester. The plugs are the correct surface gap plugs. I also tried putting fuel/oil mix in the cylinders and still nothing. I cleaned all the ground connections and I put an ohm meter between the + and - sides of the coils and everything looked good except when I put the ohm meter between the + and the plug wire or the - and the plug wire on the #2 cylinder it was dead. However when I make the same connection on the #1 coil I get a reading