1980 Johnson 140 hp compression test-how

[Jim Robbins]

I'm going to look at a ($1000.) 1980 Johnson 140hp outboard motor and I would like to know how to do a compression test and the ( + / - %) between each cylinder reading?
If I read ___,___,___,___ numbers, do not buy or OK to buy?
What else do I need to check out?

I have a blown 1892 Evinrude 140 hp motor, How can I find out if they parts will fit on the 1980 Johnson 140 HP motor. Thank-you

 

[tashasdaddy]

Re: 1980 Johnson 140 hp compression test-how

cross reference parts here: http://www.evinrude.com/en-US/Accessories/Literature/

what i do is remove the spark plug wires, and arrange them so they will not ground out. then remove plugs. then test compression 4 -5 revolutions each cylinder. your looking for 100 psi plus, the higher the better. and need to be in a range of 10% of each other. you have to take inmind that every compression tester is a little different.