Compression readings on my 1984 90hp

[ricohman]

Last night I rebuilt the carbs on my 1984 90hp as it was would not idle. Now it starts instantly with a touch of the key. The idle is good now but I'm not sure if this V4 is supposed to shake a bit at idle. It certainly is smoother than my old merc tower of power and my 40hp Johnson but it does shake a bit at idle.
Anyway after it was warm I decided to do a compression test. here are the reading.
#1- 125 psi
#2- 125 psi
#3- 130 psi
#4- 120 psi

It appears I have a 10psi difference on that lower cylinder. Is this something to worry about? I have read horrr stories about guys ignore a low readign and destroying their motor.
This motor runs a VRO pump which appears to be an upgraded ethanol fuel type.

 

[boobie]

Compression looks good but if it was my motor I'd do a good de-carb on it.

 

[ricohman]

Compression looks good but if it was my motor I'd do a good de-carb on it.

Not sure what that is? Additives?

 

[GA_Boater]

Boobie is talking about Seafoam or another cleaner to put in the tank.

 

[ricohman]

Boobie is talking about Seafoam or another cleaner to put in the tank.

Ahh. Something that could free up a sticky ring and gum. This motor has really not been used much. And not much in the last 15 years.

 

[interalian]

Those are great numbers for low-compression heads.

 

[boobie]

That's why a good de-carb wouldn't hurt it. JMO. Get some BRP Engine Tuner, follow the directions on the can and run that through it.