199x 70hp johnson

[dieselcat]

I am going to look at a 1990's johnson 70 hp outboard this weekend with possibility of purchasing it and am going to do a compression check.can someone tell me what numbers I should be looking for on compression?

Thanks in advance

 

[boobie]

Re: 199x 70hp johnson

No more than 15 psi variation between cyls. Post back with your #'s.

 

[dieselcat]

Re: 199x 70hp johnson

Will do

 

[dieselcat]

Re: 199x 70hp johnson

Ok boobie im going to look at motor now and am not gonna have the luxury to post psi numbers so can u tell me how low of compression is to low.the guy told me when he checked it when he purchased it that it had 95-100 psi per cylinder. ..

 

[boobie]

Re: 199x 70hp johnson

His #'s sound okay but what are they now ?? You can rent a compression gauge from most parts houses,

 

[dieselcat]

Re: 199x 70hp johnson

Ok checked it,it seemed good to me top cyl 98 mid cyl 94ish bot cyl 98

 

[JB]

Re: 199x 70hp johnson

Gauges, conditions and techniques vary too much to put criteria on psi, but since there is no variation from cylinder to cylinder it is the spread that matters. Done this way http://forums.iboats.com/engine-frequently-asked-questions-faq/compression-test-jb-391323.html the spread should be 10% or less.

It is near impossible for three cylinders to go bad by the same amount at the same time so don't fret about psi unless it is down to around 70-80psi.

EDIT: You posted while I was typing. Those numbers are fine.

 

[dieselcat]

Re: 199x 70hp johnson

Thanks for the speedy feed back,I really appreciate it!