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Whitecap36, Marine Technician
Category: Boat
Satisfied Customers: 1545
Experience:  28 years Certified Marine Technician and past FL State Certified teaching degree
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What should compression be on a merc 2000 225 efi engine

Resolved Question:

What should compression be on a merc 2000 225 efi engine
Submitted: 7 years ago.
Category: Boat
Expert:  Whitecap36 replied 7 years ago.
As compression is not a recommended test for an outboard engine there are no such spec's in the Mercury service manual. We have seen case after case where good compression reading are dismissed with poor leak down test readings. The only accurate compression reading is a bad or low reading. So before you make this boat purchase I recommend taking to a dealer that will check over including performing a leak down test.

To understand the leak down test better we first run the engine to operation temp and remove all spark plugs. We then pressurize one cylinder at a time with the piston at TDC and read the percentage of leakage as we move the piston down to the ports and back. This is a very accurate test and is recognized by all marine engine manufactures.

Edited by Mike on 12/4/2009 at 5:33 PM EST
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