Compression?
 

Can anyone tell me what the compression is supposed to read for a 50 hp mercury? Picking up the new motor tomorrow afternoon and would like to check the compression before I drop the cash. Motor looks very clean and seller says less than 100 hrs but still want to verify.

Google ?

just make sure there is not more than a 10% drop between cylinders. Clean does not mean anything believe me

best i can find, sounds about right to me though but im no mechanic

Going to rent a tester from Oreilly tomorrow on the way to Prien lake, never done it before. Figure all I have to do is pull the spark plug hoods and hook the tester up working from top to bottom and spin it, correct?

You have to pull each spark plug and screw the threaded end of the tester into to spark plug hole. The dial gauge is the other end of the tester. Normally, you would want to turn the motor over at least three times to record the compression.

Have it checked out by a mechanic.....it'll save ya money in the long run........trust me......Tim

Ran motor on sellers boat down at Black Bayou south of town, water was almost all gone. Did not run long or far enough to get it very warm but did check compression on all 3 cylinders. All were at 100 not the 120 everyone said I should see. Anyone have any suggestions, still am go unless the gallery says differently.

were all 3 exactly on 100? some motors read low like that..and also there can be a difference in reading between different compression gages...i'd try another gage and see the difference..

if all 3 were exactly at 100..thats a good thing, i personally like to see higher than 120 though..its rare that a motor will wear down all 3 cyls evenly.....which would mean to me that its one of those motors that read low or the gage reads low...

Indicator gage needle was between 95 and 120 consistently on all three. O-ring was worn on plug and only hand tight which could explain the low reading??