compression

C

cavy

Recruit
Joined
May 14, 2008
Messages
5
Hello

I have a 1993 mariner mag 3 150 hp. I decided to to a compression test.
I took all the spark plugs out and measured each cylinder. i got between 70 and 72 on all six cylinders. What should it be? Does this seem low?

Jim Cav
 
Barnacle_Bill

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: compression

That is low. How many times did you let the motor turn over when getting a reading? I usually let them turn over until the gauge stops rising.
 
S

Steven1962

Seaman Apprentice
Joined
May 23, 2008
Messages
34
Re: compression

It does not matter what your numbers are, what matters is that they are all close to the same. not more that 15 psi differance between them. All gauges very, all people do things a little different. If they are all that close you are good.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: compression

Lower compression "readings" do not mean lower compression, cavy. They are simply readings. That is what Steven is saying.

The purpose of compression checks on 2 strokes is diagnostic. . .is there a bad cylinder or two? In your case the answer is no, there is not even one bad cylinder.
 
T

thefairlaneman

Banned
Joined
Sep 5, 2007
Messages
1,790
Re: compression

The low numbers as others have said can be misleading. Dont forget when the engine reaches its running temp to pressures will go up. Sounds like you dont have a problem.
 
B

bchoate

Cadet
Joined
Apr 28, 2008
Messages
25
Re: compression

Sounds like you have a bad guage. The compression reading on that engine should be about 115 to 125. But as long as all are within 10 to 15 percent as noted in previous posts it sounds normal. Try a different guage.
 
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