Compression Numbers - Are these bad?

F

Fl_Richard

Lieutenant

Joined

Jan 21, 2005

Messages

1,428

• Dec 26, 2006

• #1

Hello everyone,

I havent really been having any problems but I boughta new compression tester and decided to try it out. Here are the numbers from my Johnson 150 (1995 Model J150EXEOM sn G03788662)

top to bottom from the rear

87 88
89 90
88 88

Any comments are gladly appriciated

 

WillyBWright

Fleet Admiral

Joined

Dec 29, 2003

Messages

8,200

• Dec 26, 2006

• #2

Re: Compression Numbers - Are these bad?

I like them.

 

S

steelespike

Supreme Mariner

Joined

Apr 26, 2002

Messages

19,069

• Dec 26, 2006

• #3

Re: Compression Numbers - Are these bad?

They are a tad low but its good they are close to the same on each cylinder.You might try a de carb to bring the numbers up.Most say 100 psi is a minimum.I'd try the decarb but wouldn't worry as long as they stay pretty even.

 

tashasdaddy

Honorary Moderator Emeritus

Joined

Nov 11, 2005

Messages

51,019

• Dec 27, 2006

• #4

Re: Compression Numbers - Are these bad?

you can use seafoam, fuel additive, and seafoam deep creep.

http://www.boatsetup.com/Decarb_Carb.html

 

iwombat

Captain

Joined

Jul 12, 2006

Messages

3,767

• Dec 28, 2006

• #5

Re: Compression Numbers - Are these bad?

They might be low just because of cranking speed. I really wouldn't worry about the values, only if they all agree. And, they do!

 

O

oleliner

Cadet

Joined

Nov 10, 2006

Messages

20

• Dec 29, 2006

• #6

Re: Compression Numbers - Are these bad?

at one time i checked the shop manual , about compression , and it stated that as long as they are within 10% of each other.. that is ok ..not to worry..

 

W

Walker

Captain

Joined

Jun 15, 2002

Messages

3,085

• Dec 29, 2006

• #7

Re: Compression Numbers - Are these bad?

They sound pretty low to me for a looper. Could be your guage and as already mentioned it may be time for a decarb

 

kenmyfam

Supreme Mariner

Joined

Aug 10, 2006

Messages

14,385

• Dec 29, 2006

• #8

Re: Compression Numbers - Are these bad?

Does sound a little low !!! there again how good is the gauge ??? I had one many years ago that read everything about 10% low.

 

E

emdsapmgr

Supreme Mariner

Joined

Dec 9, 2005

Messages

11,551

• Dec 31, 2006

• #9

Re: Compression Numbers - Are these bad?

Did you have all plugs out of the engine when you did the test? Static compression depends on starter speed. It's spinning speed is much slower with all the plugs in.

 

tashasdaddy

Honorary Moderator Emeritus

Joined

Nov 11, 2005

Messages

51,019

• Dec 31, 2006

• #10

Re: Compression Numbers - Are these bad?

there are no to testers that read alike, hot engine vs cold engine, all relative. being equal is more important than the number. unless all are 50, then consult another tester.

 

JUSTINTIME

Captain

Joined

Sep 2, 2006

Messages

3,284

• Jan 4, 2007

• #11

Re: Compression Numbers - Are these bad?

did u have the throttles wide open?
u will get different readings also