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Compresion on 1989 mercury

M

marriog207

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"Sorry maybe I asked the wrong

"Sorry maybe I asked the wrong way earlier.
Can you tell me if these compression readings seem ok, and why would #2 be 150,#4 145 and #6 120, I had all the plugs removed and motor was cold, could that do it, this is what the readings were.
The left side from behind outboard read top to bottom,
#1 - 130, #3 - 130, #5- 120,.
The right side top to bottom
#2 - 150, #4 - 145, #6 - 120
Thanks M"
 
"Nevermind, I looked at a few

"Nevermind, I looked at a few other compression posts from this one, and other sites, it more less tells tells me mine are fine.
Thanks for all your help and advice, gentlemen talk to you later."
 
"Mario...
I don't want to

"Mario...
I don't want to scare you but....
#2 = 150 and #5 & #6 = 120
You may have worn rings or reeds on the low ones, or excessive carbon build up on the high one. It might run forever like that, or it may cause a big problem some day. You normally look for no more than a 10% difference between highest and lowest. Warm the engine up and try a cyl. leak down test to see where the compression is going on those low cyls. If it runs good, you may get away with it, but keep it in the back of your mind that there could be something going on in there.

Wrench"
 
As far as I know reed valves a

As far as I know reed valves affect crankcase compression and have nothing to do with cylinder compression while testing.
 
London...
You're right. I

London...
You're right. I stand corrected. I had a momentary laps of brain power there. Reeds are for the crankcase and not cyl compression. I should do some more sudoku to keep my brain sharp.

Wrench
 
"Thanks Wrench and London Mari

"Thanks Wrench and London Marine,
so should I get into decarbing all the cylinders, and replacing all the rings I wonder if sitting for 15 yrs ate up the the lower rings or what? And is this an expensive process, (any estimations helpfull and aprieciated) I have taken apart many automotive engines and put them back together, but never taken apart an outboard.(I have to get a repair book on this outboard).
Thanks M."
 
"Sorry, new question how do I

"Sorry, new question how do I do a cyl leak down test?"
 
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