Your opinion on this compression reading?

[Pleasure Boat Junction]

I just checked the compression on this new to me 71 evinrude 60hp. The compression readings are as follows:
1: 150
2: 170
3: 169

What would you do?
Also, in several post this motor is called a looper. Could somebody explain what that means?

 

[Joe Reeves]

Re: Your opinion on this compression reading?

The term "looper" pertains to the way the fuel mixture enters the combustion chamber.

There is a 20 psi difference between the lowest and highest compression reading....... not a good sign.

 

[Pleasure Boat Junction]

Re: Your opinion on this compression reading?

No, probably not good. Would you run it as is or tear into it?
Wasn't sure what looper meant. Saw it posted several times and googled it and came across the Quincy Welding sight. I didn't think it had anything to do with their type of motors.

 

[Carbkid]

Re: Your opinion on this compression reading?

Did you check compression cold or hot. I would run it and check the results after it cools down. If it were me I would run the motor as is. I personally don't think 20psi difference is that bad.

 

[karlow1]

Re: Your opinion on this compression reading?

De-carb it, and recheck.
Then I would live with the results!
But then, what do I know!

KP

 

[Pleasure Boat Junction]

Re: Your opinion on this compression reading?

Checked it cold.
What is the procedure for De-carb?
Do those readings seem high? I don't have anything to compare it against, but I wasn't expecting numbers that high.

 

[jonesg]

Re: Your opinion on this compression reading?

compression guages are known to be wildly variable.
The first test on my engine showed 30 psi !,
the next guage we tried showed 65psi.
Did a decarb and it jumped to 70,
did it again and bought a new guage 85psi.

Low but they are all closely grouped around 85.
And it runs good.

I would get a can of seafoam and follow the directions, half in the tank and shoot some in the cylinders, let it soak then run it whilst spraying some into the carbs. It gets the carbon out and will free up any stuck rings.

 

[Pleasure Boat Junction]

Re: Your opinion on this compression reading?

Same gauge on my 40hp got 95 per cylinder

 

[mthieme]

Re: Your opinion on this compression reading?

Rule of thumb, 10% difference tolerance. You're just beyond this.
Given it's age and if it ran, well - I would just go ahead and use it.
If it's been sitting for a while, the readings could easily change after a little loosening up.

 

[Pleasure Boat Junction]

Re: Your opinion on this compression reading?

Ok, I ran it for about a half hour in a tank and checked the compression hot.
As follows:
1: 140
2: 160
3: 157

When I say hot, I mean as hot as it would get. The head is just warm to the touch. I think maybe the thermostat is stuck open.
Is the seafoam available at most boating stores? I'll give it a try if I can find it.

 

[Joe Reeves]

Re: Your opinion on this compression reading?

That 20 psi difference is still there. At a minimum I'd suggest removing the cylinder head to check the head gasket, sealing surfaces, etc. There's always a chance that a slight flaw exists that can be corrected to prevent further damage. And if not...... you've lost nothing except the price of a head gasket and some time.