Compression 90 9.9 Johnson

Bob dobolina

Recruit
Joined
Dec 11, 2018
Messages
3
Recently purchased ‘90 Johnson 9.9. Compression reads 80 psi in both cylinders. My cousin Freddy says I need at least 95 psi. Can anyone help?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
Fire the cousin.-----Does the motor run properly ??-----Is your gauge accurate ?-----Did you try pulling it over a little faster ?
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,914
did you cousin Freddy :target: make you an offer to get off your hands ?? :nod:
 

Bob dobolina

Recruit
Joined
Dec 11, 2018
Messages
3
Thanks. I will try pulling faster. It seems to run fine. The gauge is brand new first time I’ve used it
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
Test with the second plug removed (both plugs out for spark testing). Crank until reading stops increasing.
 

wannabewelder

Seaman
Joined
Aug 10, 2018
Messages
71
Did you do a wet test with oil? Shoot some WD in the hole, turn over to lube and retry.
I have 3 compression gauges with 3 different readings. 1 is old and 20lbs low. I use it for dead heading gaskets and cracks.
 
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