200 EFI Compression Question

[tmanala]

I have a 1999 Mercury 2.5 Liter 200 EFI (20" Std Rotation) motor that has been sitting on a motor stand for almost two years in my garage.

During this time the spark plugs were out of the engine.

I am selling the motor with a project boat and decided to check the compression on the motor.

I checked the cylinders and walls - all clean no scratches or marks.

Connected remote maintenance starter switch and battery to motor and did a compression check.

At first the motor did not turnover as quickly as I thought it should as I was using a new cranking battery.

Then after a few tries it jumped up and started turning over as you would expect a Mercury should spin.

Here is the findings for the two test passes I ran.


<tbody>
Cylinder
1st Check PSI
2nd Check PSI
% Increase


1
80
110
+27%


2
50
75
+33%


3
40
85
+53%


4
80
100
+20%


5
115
140
+18%


6
110
120
+8%

</tbody>


Is this normal for an engine that has been setup for so long.
It seems like the rings may be stiff and are getting loose the more we turn it over and sealing better.

Would one expect that if we cranked the motor and got it up to temp that the rings may all seal bringing the PSI up to normal numbers?

Any thoughts from the Certified and Experienced Mercury techs who travel through this blog.

[outasite]

My first impression would be that there was some rust you did not see.Two years and no plugs,good chance of moisture.It may be just dry but! If your going to sell it, pull the heads and take a look.

[tmanala]

thk... I did pull the heads and looked at cylinder walls they looked clean....

Not selling as a running motor but just want to make sure next guy has accurate information about what he is getting.

If I pull pistons and put new rings then get running I'll sell the motor as complete running motor and not project.

[outasite]

If the walls are ok you can go in through the front for rod bolts pull piston & rod, out the back for a re ring.Put some paper towl in the ports and scotch bright the walls.Just keep it clean!

[kingsbiship]

Run some 'Sea Foam' thru it for a while! It'll clear up and give better compression results!

[CharlieB53]

Oil the cyls, all of them.

Rig fuel with SeaFoam for a decard, add water, fire it and run at moderate to fast idle varying speed.

Retest compression.

[tmanala]

Thanks for the advice... ordered some new rings and will re-ring all six and clean up cylinders....

Hopefully that will bring up compression.

I am also going to pull injectors and send them off to be serviced/cleaned.

Get motor running and be in god shape.

Let you know how it goes.