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Max Online: 36273 @ 01/23/13 02:34 PM
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#12348978 - 07/19/17 08:37 PM Mercury compression specs???
i-Fish Online   content
Pro Angler

Registered: 06/07/16
Posts: 884
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...
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#12348985 - 07/19/17 08:40 PM Re: Mercury compression specs??? [Re: i-Fish]
i-Fish Online   content
Pro Angler

Registered: 06/07/16
Posts: 884
Or is it just commonly accepted to look for anything over 100 psi and each subsequent piston to be with 10% of each other?


Edited by HookinToads (07/19/17 08:40 PM)
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#12349121 - 07/19/17 09:25 PM Re: Mercury compression specs??? [Re: i-Fish]
grout-scout Offline
TFF Celebrity

Registered: 12/08/08
Posts: 6939
Loc: Boerne, Texas
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.

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#12349254 - 07/19/17 10:38 PM Re: Mercury compression specs??? [Re: i-Fish]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11439
Loc: Littlefield Tx & Lake A. H. US...
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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The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD

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#12349484 - 07/20/17 07:57 AM Re: Mercury compression specs??? [Re: i-Fish]
Muzzlebrake Offline
Extreme Angler

Registered: 12/26/14
Posts: 1664
Loc: Euless
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.
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From Genesis: "And God promised men that good and obedient wives would be found in all corners of the earth."

Then He made the earth round...and He laughed and laughed and laughed!


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#12349561 - 07/20/17 08:47 AM Re: Mercury compression specs??? [Re: Muzzlebrake]
Rick Collis Offline
Pro Angler

Registered: 02/09/07
Posts: 524
Loc: Lake Fork, Texas
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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#12384320 - 08/13/17 10:57 AM Re: Mercury compression specs??? [Re: i-Fish]
Gamblinman Offline
TFF Team Angler

Registered: 11/26/02
Posts: 3482
Loc: Yantis, TX
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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