View Full Version : Compression test results.

Lowell Bernhardt
11-19-2002, 08:12 PM
Today I finally got a compression guage to test ye old Mercury.

Well, let's just say that now I have a compression guage. :(

I tested all 6 cylinders and thus far I'm not too impressed. I didn't get any really what I thought were good readings. #s 3 & 4 are reading about 15 pounds lower that the others. They all read better when the cylinders are shot with oil. From what I hear this could be one of two things. Rings that are stuck and or not doing their job. Or scored cylinder walls. I'f it's the latter does anyone need a 300# paper weight? It'll hold down a BIG sheet of paper.

I'm hoping that the rings are just stuck from sitting in the barn for 5+ years. I would think that they would break loose over use of the motor?

I guess I'm going to proceed with the test fire this weekend (hopefully). If I can get it to fire and turn over this weekend I guess that it would be worth a new set of rings.

Any suggestions would be greatly appreciated as always. Do you all think I'm nuts?


11-19-2002, 08:27 PM
Mouse Milk. Give it some Mouse Milk. Or is it Marvel Mystery Oil? One of 'em is sure to free up them rings.


Peter Malcolm Jardine
11-20-2002, 12:00 AM
it could be a stuck ring. If you can get it running, you will probably find that it will improve. Hey if it runs and doesn't blow a lot of oil, who cares? if you are that close to running it, sounds like you are doing all right. Those older engines are not as sensitive to a compression loss as the new injected ones are. computers arrgggh. Yours will probably run with one or two cylinders down 30 pounds

Peter Malcolm Jardine
11-20-2002, 12:02 AM
by the way thats a :cool: motor. I bought one out of the paper once for 50 bucks, but the bottom end was seized so hard I couldn't even get it apart... but 300 pounds of aluminum got me my money back anyway. Good luck

Peter Malcolm Jardine
11-20-2002, 12:04 AM
Oh and diesel fuel or transmission fluid is the best for freeing up rings. pour it in and let it sit in the cylinders for a bit. diesel would be best in your case.

Sam F
11-22-2002, 04:35 PM
Try Marvel Mystery Oil.
I've seen it do amazing things.
Next door to an old job, a guy brought in a Model T based truck that had spent ages sitting out in a field. Trees had grown through the bed and the cab basically fell off when he brought it into the garage. The engine was seized up of course.
He poured MMO everywhere, on and in that engine.
He let it sit a few days and then started cranking... yes that's with the hand crank. I went over and helped on my break and about wore my arm off but it kept sputtering and before the day was over it started and ran rather well.