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

M

mattsjohnson

Cadet
Joined
May 27, 2011
Messages
9
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

lindy46

Captain
Joined
Nov 27, 2008
Messages
3,886
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.
 
E

eddie_m

Cadet
Joined
May 6, 2010
Messages
15
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
 
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