Mercury Compression

[jorgeinmiami]

I have a 1992 Mercury 200 Offshore outboard that I ran a compression check over the weekend.

All cylinders came out at 110 psi.

Im not sure if this is good or not.

What would be a indication or where should they be?

[DonV]

Well....that's very good! One question, don't take this wrong because I did this myself on a tire pressure gauge years ago, did you release the pressure on the gauge after each cylinder? Seldom are they all the same to the exact pound. My 225 EFI was no more than 5 psi between high and low and I was very happy.

[jorgeinmiami]

Yes I released the pressure in between each

Now they were not all exact but the difference was so little less than 5 psi

[Bigshrimpin]

Originally Posted by jorgeinmiami

I have a 1992 Mercury 200 Offshore outboard that I ran a compression check over the weekend.

All cylinders came out at 110 psi.

Im not sure if this is good or not.

What would be a indication or where should they be?

There are some 2.5L 200's that have lower compression. I'll check to see the number on the heads. I have two 1992 2.5L 200hp in my garage compression is even on both engines right at 110psi.

[flyingfrizzle]

More even the better, A lot of the latter 2.5s should have 120-130 per cylinder and you want all of them with in 10%. The 1992 year compression could be a little lower than the latter years 2.5s but 110 is not bad if even. Seems like the 1991 year had a ton of changes or variances but the 1992 model should be more standard. Never the less if you are with in 5 psi of each hole I would be happy. A leak down test will give you a little better idea of what the bores look like but the 2.5s live forever if taken care of.

[gofastsandman]

Great numbers for OMC.

Mercs of that vintage tend to be a bit higher.