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Mercury compression specs??? #12348978 07/20/17 01:37 AM
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i-Fish Offline OP
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Where in the world can I find compression specs for a 2014 Mercury 150? Testing a motor tomorrow and I ain't got time to buy a manual...


If you can't find em wind em.
Re: Mercury compression specs??? [Re: i-Fish] #12348985 07/20/17 01:40 AM
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i-Fish Offline OP
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Or is it just commonly accepted to look for anything over 100 psi and each subsequent piston to be with 10% of each other?

Last edited by HookinToads; 07/20/17 01:40 AM.

If you can't find em wind em.
Re: Mercury compression specs??? [Re: i-Fish] #12349121 07/20/17 02:25 AM
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grout-scout Online Sleepy
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You have to test compression on mercs in a very particular way. You can't just stick a gauge on them and get an accurate reading.

Re: Mercury compression specs??? [Re: i-Fish] #12349254 07/20/17 03:38 AM
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gary purdy Offline
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A leakdown test is the only true test of a cylinders condition. A simple sparkplug out cranking speed compression test is a starting place, then check each cylinder at full throttle, then leak test, if an abnormality is found then bore scope.


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Re: Mercury compression specs??? [Re: i-Fish] #12349484 07/20/17 12:57 PM
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Muzzlebrake Offline
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Cranking compression will be different between 2 strokes and 4 stroke engines.
Ballpark, you might see 120 on a 2s and as much as 175 on a 4s.


From Genesis: "And God promised men that good and obedient wives would be found in all corners of the earth."

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Re: Mercury compression specs??? [Re: Muzzlebrake] #12349561 07/20/17 01:47 PM
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Rick Collis Offline
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It depends on how you take the compression. There are several methods. The best engine I ever owned was a 225 Optimax. It had between 90 and a 105 lbs compression shortly after it was brand new. It is still running great with over 1700 hrs. So don't get too carried away with numbers. As already stated all cylinders should be fairly close.


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Re: Mercury compression specs??? [Re: i-Fish] #12384320 08/13/17 03:57 PM
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Gamblinman Offline
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Motor hot, kill switch pulled, throttle wide open, All plugs removed...test each cylinder. You should be looking more for a wide variance between cylinder pressures.

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