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Author Topic: HOW DO YOU COMPRESSION TEST OUTBOARD?  (Read 1402 times)

April 20, 2011, 09:25:46 PM
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dtuck

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HOW DO YOU COMPRESSION TEST OUTBOARD?
« on: April 20, 2011, 09:25:46 PM »
How do you use a compression tester? Do you unscrew spark plug/attach(screw in)tester than crank motor?  What compression number am I looking for on a 150hp Johnson Ocean Pro?  Do I test each cylinder individually? Thank you for all of your help. D
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April 20, 2011, 09:34:46 PM
Reply #1

seabob4

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #1 on: April 20, 2011, 09:34:46 PM »
You can do it simply by pulling the kill switch lanyard, this allows the motor to crank but not turn over...

Remove a plug, screw in the compression tester, crank for about 8 secs., note the reading.  Repeat for all cylinders...

What you are looking for is consistency across the board.  Could be from around 100 to around 120.  What you DON'T want to see is a cylinder that is way off (low) from the others...
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Corner of 520 and A1A...
April 20, 2011, 09:59:37 PM
Reply #2

LilRichard

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #2 on: April 20, 2011, 09:59:37 PM »
Its also best to warm the boat up first...
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April 20, 2011, 10:44:20 PM
Reply #3

seabob4

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #3 on: April 20, 2011, 10:44:20 PM »
Quote from: "LilRichard"
Its also best to warm the boat up first...

^^^^^ :thumleft:
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Corner of 520 and A1A...
April 20, 2011, 10:54:03 PM
Reply #4

flounderpounder225

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #4 on: April 20, 2011, 10:54:03 PM »
Make sure you take all the plugs out on each side (all 3 on your 150) while testing that "bank" if a head gasket is suspect, by not taking the adjacent plug out, the compression from the tested cylinder could possibly leak across to the other cylinder, build pressure and give a false positive reading.  Also, have the throttles opened all the way up, all of this eliminates possible false readings and isolates each cylinder as best as possible.
Marc
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Marc
1997 245 Osprey, 250 HPDI.  SOLD
April 20, 2011, 11:12:58 PM
Reply #5

seabob4

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #5 on: April 20, 2011, 11:12:58 PM »
Marc,
If dtuck is talking about Alex's 200 Osprey, then he should be good to go on a standard comp test with no known head gasket issues.  The motor was in great shape and ran like a champ when I had her for a "tidying" of the wiring...
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Corner of 520 and A1A...
April 21, 2011, 08:28:50 AM
Reply #6

dtuck

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #6 on: April 21, 2011, 08:28:50 AM »
Alex decided to keep his 1986. Probably all that great rigging done by SeaBob. Cant say that I blame him-I wouldnt have sold her either. The boat I am currently looking at has been sitting for a few years-that concerns me a bit-I will warm up engine-than pull each side of plugs/test each cylinder and see how it goes.  Any addl. advice would be great-keep it coming-Thanks, Don
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April 21, 2011, 09:22:14 AM
Reply #7

slvrlng

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Re: HOW DO YOU COMPRESSION TEST OUTBOARD?
« Reply #7 on: April 21, 2011, 09:22:14 AM »
Here is a link over to iboats about compression testing. Its pretty much what everybody has already said. If you check this area of iboats there are a lot of tests and procedures listed that could help.

http://forums.iboats.com/showthread.php?t=391323
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Lewis
       1983 222 Osprey "Slipaway"
       1973 19-6 "Emily Lynn"
      
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