20hp johnson wont start. plug wires, compression issuse.

[mattsjohnson]

Hi guys, I recently posted about a 1966 20 hp johnson that had 58#s, and 60#s of compression on cylinders, good spark but wouldn't start even if I sprayed gas or starting fluid in the carb. only a backfire. I was concerned with the compression,(if it was enough to start?) but some one replied about the clue of the backfire and questioned the plug wires, I only assumed the wires were hooked up right when I bought it. WRONG!! 60lbs. is enough compression to start but you wouldnt want to run it long without a rebuild. Oh and the rear coil matches to the top cylinder. and the front coil to the bottom. I hope this helps someone as it did me. Thanks.

 

[lindy46]

Re: 20hp johnson wont start. plug wires, compression issuse.

Front coil fires the top cylinder. Try placing the motor with the cylinders pointing up and pour a small amount of Seafoam in each cylinder. Let soak a day or two and re-check compression.

 

[eddie_m]

Re: 20hp johnson wont start. plug wires, compression issuse.

It could be an easy fix Seafoam does work i learned about it on this site and have used it . It could be the head gasket