Compression test

SweeperForce

SweeperForce

Chief Petty Officer
Joined
Feb 7, 2010
Messages
487
I hate to ask but I can't find the post on the procedure.
I finally bought a nice screw-in comp tester. 0-370 psi. It came with 10mm,12mm,14mm,14mm long, and 18mm tread adpators. I hope one of those will work. I plan on doing this Saturday. I'm not sure what to ground, how to ground, motor hot, motor cold, dry, wet, use WD-40?
Can someone please give me step by step instructions on how to do a compression test?



Thanks,
Tom
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,926
Re: Compression test

I do mine with the key off.That way i don't have to ground out the plug leads.
Remove all the plugs.Get a jumper wire or jump box.
Screw in the tester,I think 14mm.
Or try until you get the right one.
The throttle open all the way(really doesn't have to be).
Then jump solenoid turning it over till it stops going up.
Then release pressure,do the next cylinder.
The readings should be close to each other.Within 5-10# of each other.
Mine all 6 read 150-155#
Your guage might read different.
I don't add any oil or WD untill after the inital reading.
If there is a problem with a cylinder then I might add oil or WD to see if it brings up the reading.
 
SweeperForce

SweeperForce

Chief Petty Officer
Joined
Feb 7, 2010
Messages
487
Re: Compression test

OK here we are
1) 151 psi
2) 145
3) 146
4) 151
5) 144
This from a slightly warm motor, I ran it for about 10 minutes in a tub on my driveway. Waited for 30 minutes, them test the comp.
The plugs looked really good, here's a pic
Compression test_0002A.jpg Compression test_0006A.jpg
 
P

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: Compression test

Everything looks good. I always do a compression test before I put the motor away for Winter. The readings have stayed the same for the past 5 years.
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,926
Re: Compression test

As long as you run good gas and don't add to much oil and don't mess with the air screws and don't troll to much keep out of the mud,sand and,and,and??
This motor will last a long time.
Just remember if it doesn't start right away!!!!
There is something wrong.Catch it early.
Oh yea flush after each use if it's been in any salt water.
 
W

wickware

Lieutenant
Joined
Jun 20, 2009
Messages
1,286
Re: Compression test

Should compression gauge adapters be compared with plugs to make sure the piston will not hit the adapters? Then make a rotation by hand before power to be positive of no contact?
 
SweeperForce

SweeperForce

Chief Petty Officer
Joined
Feb 7, 2010
Messages
487
Re: Compression test

I lined up the threads and contact point before I inserted the adapter. They were spot on, if anything they might have been 1/32 over.
Put the plugs back in and it turned right over. I then put half a gallon of fuel,oil,stabil, and seafoam in my spare tank. Started it up, put some seaform in a spray bottle and hit each of the carbs. Shut it off and waited 30 minutes. Started it again, ran the spare tank almost out. Then I switch to my main tank and ran that for a while to get rid of any lingering seafoam and/or deposits. After the treatment I swear it sounds better and runs better. The real test will be next weekend.
Thank you all for your help and comments.

Tom
 
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