Normal cylinder pressure for 6.2?

[MAKC]

I was looking for, but not able to find, anything that would indicate the normal pressure for the cylinders of a 6.2L on a 2005 model. Engine survey showed 1 cylinder at about 75 where the others were twice that (give or take a few psi). Anyone know what they should be at?

The dealer is going to take a long look at it tomorrow to figure out if it was a misreading or it really is a problem. I'll keep my fingers crossed for something simple.

Thanks

Mike

 

[H2ONUT]

I'd say anything in the 150ish range is what you need. If one cylinder is reading 75, I would suspect a cracked valve.

 

[Nehalennia]

yeah, 150-175

 

[gmurtic]

Hello from Croatia!!!
Not many manufacturers give what the pressure should be, but that it should not vary more then 15-20%
Your problem is most likely the valve if the reading is correct, but what you need to do first is heat up the engine on operating temperature before measuring.
How long was the engine sitting? This is what happens if the engine was not properly winterized.
If you get the same reading I would suggest the following;
Take off the spark plug and squirt some oil into that cylinder, and check again, if the pressure rises you have bad rings, if not it is the valve...
If it is the valve, there is a possibility that it is stuck inside the valve guide, there are ways to loosen it , but in most cases it is already bent from hitting the piston...
If the rings are the problem, try to run your engine without load for a few hours under various rpm, but not more that 3000, maybe the rings will loosen.
If the valve is a problem you need to take the head off and rebuild it, don't rebuild only one, do both, when you remove everything from the engine to get to one head, you don't have much to do to take the other one off, parts are not expensive do do complete heads rebuild.

I hope that it was only bad reading!

Best regards, Goran!

 

[Newbie]

Sounds like its time for a leakdown test. Basically, you apply air pressure to the low cylinder and determine where the leak is going to. Into the coolant, bad head gasket. Into crankcase, compression rings. Into intake or exhuast manifold, then its intake or exhaust valves. I can't think of any way off the top of my head you could get a false reading on a compression test. Typically though, if its a head gasket the cylinder next to it would be low also. My first guess would be to say a valve. I have always been told compression reading should be within about 10% of each other. If you get 150 for most, the lowest you would want to see is 135. SB

 

[270SLX]

My 2006 6.2 has failed a leakdown test as well. I should know this week what the cause was. I'll let you know.

Dennis

 

[270SLX]

I meant to say I have a 2005 6.2. Not 06.

 

[Nehalennia]

I meant to say I have a 2005 6.2. Not 06.

Didn't you just have the complete hull redone?

 

[270SLX]

Yep, Todd, the complete hull has been replaced, I guess, but the boat has not yet returned to Wakeen's Family Boating from the SR factory in Knoxville. It should show up any day. The engine is another chapter in my "SAGA".

The engine always wanted to stall when cold. It was worked on twice then, last November, Wakeen's Mercruiser guy came and got my boat from my marina to do a leak down test. He wasn't happy with what he had done for my boat previously so he took it upon himself to go further. Good for him. I think he had circumvented the feature that slows the idle speed when the boat is shifted to give that smooth shifting the newer mercs have. So, he felt guilty, I guess, from not solving the problem and circumventing a desired feature to get the desired result.

It took a while for them to get around to the leakdown test so I visited my boat while it was awaiting this test. That's when I spotted the cracks in the hull that had returned even after the SR factory team had "fixed" it with lots of fiberglass reinforcement in the bottom of the hull. Then, the engine was tested and sure enough failed the leakdown test.

Fast forward. The boat went to Knoxville for a new hull and the engine was shipped back to Rock Island for tear-down to determine why it wouldn't hold compression. Today I was told that the cylinder walls were scored and glazed and I'm getting a new long block. So, I'll essentially have a 2005 boat with a 2008 hull and engine. And, it will be blue instead of cinnebar.

Sea Ray and Mercruiser stand by their products.

Dennis