Odd Compression Test Results

[AnglersEdgeNY]

The motor is a 86 Johnson 225. The compression test I did yesterday gave me an odd result. I used the old gaskets which where removed and put back a couple of times for the test (not the best idea).

First test showed
Cylinders 1,3,5 at 78,85,90 and Cylinders 2,4,6 at 56,55,63.

The second test after tightening the bolts a little more (I didn?t have a torque wrench with me, we were there to do other work but my friend brought a compression gauge so we were curious)

Second test showed
Cylinders 1,3,5 at 90,94,110 and cylinders 2,4,6 at 45,105,75

Why would cylinder #2 go down after tightening the bolts when all the others went up?

Also since the lower unit of off the motor can a hose be connected directly to the water tube to run the engine.

 

[rick_l]

Re: Odd Compression Test Results

Unless you have a bad compression tester sounds like you have problems. When you repeat the compression test do you get the same results. You should not have that much difference between the cylinders.

 

[Joe Reeves]

Re: Odd Compression Test Results

The cylinder head bolt torque and the sequence that they're torqued are critical. Simply tightening them, especially not in sequence is not a good idea to say the least.

Bolt torque is 18 to 20 foot pounds, and the tightening sequence is:

9....10

5.....6

1.....2

4.....3

8.....7 Continue on in an ever widening circle.

If those old gaskets are sealing properly, and you still have readings as you mention above after tightening the bolts properly with a torque wrench, the engine has problems.

When time permits, visit my store (copy/paste) at: stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

 

[AnglersEdgeNY]

Re: Odd Compression Test Results

I plan on running the test again this week. This time with new head gaskets, my torque wrench and using the proper torque sequence.
I'll see if I get the same erratic readings.

Thanks

 

[AnglersEdgeNY]

Re: Odd Compression Test Results

I purchased new gaskets and torqued them down properly.
A dry test of the cylinders 1,3,4,5 and 6 gave a reading between 90 and 100. Cylinder 2 gave a reading of 50. A wet test of cylinder 2 gave a reading of 70.
I thought it might be a stuck ring so I soaked it in Marvel Mystery oil overnight. Next day test showed same result 50psi.
All of the cylinders look exactly alike. There is no scoring on any of the bores, the pistons are clean ( I can read the stamped lettering).
I am debating two options
Hone all the cylinders and install new rings and pistons or install new rings on #2.
The crosshatch pattern is not visible on any of the bores.
Would a light honing, just enough to create the crosshatch pattern change the size of the bores that I would have to go to oversized rings and pistons?

 

[Joe Reeves]

Re: Odd Compression Test Results

That low compression does indicate a problem but your thoughts are headed in the proper direction.

Regardless of what procedure you decide upon, it will be necessary to tear the engine completely down. It's usually not necessary to replace the pistons unless they're scored, damaged in some respect. Just a case of cleaning them properly and installing new rings.

Those new head gaskets...... they can most likely be used again if torqued in the proper sequence.

Let us know what you find.