1970 4 hp Johnson

[mamarat]

What is the compression on a Johnson 4 hp suppose to be i have one with just 70 pounds that's not good is it ? It has been run hot but I but on a new head gasket and had the head resurfaced.. Thanks for any help.

 

[Boobie]

How's it run ??

 

[mamarat]

It don't run... think I have a bad tester I checked again and it was 50 on both cylinders.

 

[racerone]

Does spark jump a gap of 1/4" on a test device ?----Inspected the coils under the flywheel ?

 

[mamarat]

Yes, It has really good blue spark.

 

[Boobie]

Squirt some fuel in the carb once and see what happens.

 

[mamarat]

Squirt some fuel in the carb once and see what happens.

Already done that it don't even try to start. has good blue spark I even tried another set of plugs. I don't think 50 pounds is enough compression for it to run what do y'all think?? I have another one just like it and it has about 90 pounds on it.

 

[Boobie]

How did you check your spark ??

 

[Snapper Fisho]

It should still start with 50psi comps, good spark and a proper functioning carby. I have an Evinrude 1969 4hp that does with 55psi compressions and I run it at a 24:1 fuel-oil ratio as those motors from that era don't have needle bearings. Here is a video of mine running:

https://drive.google.com/file/d/1wwh...ew?usp=sharing

From my thread here: http://www.marineengine.com/boat-forum/showthread.php?470542-Advice-on-1969-Evinrude-4Hp

 

[racerone]

Do a compression test with rope directly on the flywheel.----If spark can not jump a gap of 1/4" on a test device you have a " no spark " condition.-----Laying plugs on the block is not a good test.----A waste of time !----With fuel in the cylinders it should bark at least.---Unless leads are on wrong plug.

 

[bigtime_mcalpine]

maybe the points have not been set correctly?