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  1. #1
    Petty Officer 1st Class 1stgenbird's Avatar
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    Default '57 Lightwin Compression Specs

    What are the factory cylinder compression specs for this motor, Model 3022? I can't seem to locate this info in my manual.

    Thanks

  2. #2
    Moderator JB's Avatar
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    Default Re: '57 Lightwin Compression Specs

    That is because there are no specs, bird. If both cylinders fit in a 10% span and over about 50psi if the test is done correctly you are fine.

  3. #3
    Vice Admiral nwcove's Avatar
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    Default Re: '57 Lightwin Compression Specs

    is 50 psi enough? or does it vary between year/model and make? always thought 80 psi with 10% +/- between cyls was kinda a "low end of the scale" benchmark to look for? (higher =better?)

  4. #4
    Petty Officer 1st Class 1stgenbird's Avatar
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    Default Re: '57 Lightwin Compression Specs

    I can't believe there are no specs. I know my 57 Fastwin should be about 120psi but 50psi for the Lightwin seems too low.

  5. #5
    Vice Admiral nwcove's Avatar
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    Default Re: '57 Lightwin Compression Specs

    Quote Originally Posted by 1stgenbird View Post
    I can't believe there are no specs. I know my 57 Fastwin should be about 120psi but 50psi for the Lightwin seems too low.
    i agree, there should be service manuals to give guidelines, from back in the day. how else could these motors be diagnosed for problems? has to be factory specs for comp!?????

  6. #6
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    Default Re: '57 Lightwin Compression Specs

    I've seen a lot of factory shop manuals, ansd don't ever recall seeing any compression numbers, likely BC of variability in individual samples. Most mechanics have a pretty good idea of where a specific motor should be from experience. The more important criteria is cylinder to cylinder variation. 50 psi is fine for a pull start motor, unless you can pull a motor over 300 rpm.
    Jim

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    OEM shop manual: outboardbooks.com or Ebay

  7. #7
    Petty Officer 1st Class 1stgenbird's Avatar
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    Default Re: '57 Lightwin Compression Specs

    I've got to dig further in my manual.

  8. #8
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    Default Re: '57 Lightwin Compression Specs

    I agree with wilde1j, I have never seen printed compression specs in all of my years working on outboards. If you are getting 50 psi hand cranking the engine you should be good.

  9. #9
    Vice Admiral nwcove's Avatar
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    Default Re: '57 Lightwin Compression Specs

    is this 50 psi an across the board thing for pull start motors? just asking, 50 psi seems soooo low for reliable running?!!! would really like to know (for future puchases of old motors) what is acceptable for comp #'s?. i've read many posts, and the lowest ive heard for a motor running ok is 60?? that even seems low for reliability. more concrete info needed here!

  10. #10
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    Default Re: '57 Lightwin Compression Specs

    I don't know about concrete info, but if I were looking at an engine of that vintage and the compression was anywhere 50 psi or above and very close on both cylinders I would consider it good. If you were to run the engine and do a good decarb, you would probably see an increase the compression.

  11. #11
    Chief Petty Officer cajuncook1's Avatar
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    Default Re: '57 Lightwin Compression Specs

    Quote Originally Posted by 1stgenbird View Post
    What are the factory cylinder compression specs for this motor, Model 3022? I can't seem to locate this info in my manual.

    Thanks
    I have a comprehensive Johnson service manual that gives all the specification from late 1940's to 1964. The guys are right, no compression figures were printed.

    I have a 1957 Evinrude 3hp Lightwin and the compression numbers are 80psi on the top and 82psi on the bottom. Now that being said, it does not mean your motor is no good. A lot variables affect compression testing. It could your guage or your technique. *** The most important bit of information is that they are 10% of each other.

    Your piston rings could be all coke up with harden carbon and preventing them from moving and effecting your compression. You can try facing your motor up (spark plug holes to the sky) and pouring a ounce of Seafoam in each cylinders and let it sit a couple of days. Replace the spark plugs back in the holes. Hopefully the seafoam with seep into the crevices of the piston rings and start to soften and dissolve the harden coke/carbon.

    A very experience lightwin AOMCI forum member stated this about the JW and Lightwin 3hp motors.

    Compression reading:

    80 to 90's psi, the motor idle very low and run like new
    70 to 80 psi, the motor will idle low and run great
    60 to 70 psi, the motor will idle decent and will run fine

    Here is a link to the Iboats article on how to decarb your motor. Very good article.

    http://forums.iboats.com/showthread....76#post2648076

    Seafoam cost about $7 or $8.00, cheap way to decarb your motor and it will certainly not harm it.

    Check your compressionnumbers after the decarbing and hopefully it will improve your numbers. Clean your plugs after you decarb the motor and torque them back to specifications.


    Just a bit of friendly advice that was given to me. If the motor is running fine, don't get caughtup with numbers. If its a fishing motor and it gets you the fishing hole and back, then great. At 50psi, it you may have to idle it a little higher to keep it smooth, then again some people don't have boats or a motor to enjoy, so enjoy it!!!
    Being cheap and not getting a manual will cost you hundreds or maybe thousands of dollars

  12. #12
    Moderator JB's Avatar
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    Default Re: '57 Lightwin Compression Specs

    Change the guage, air temp, barometric pressure, engine temp, arm pulling the string or technique in some other way and PSI measured WILL CHANGE, But if the cylinders are close the engine is good.

    The only way both can be low (Which WILL be under 50psi) is when the head gasket is blown between cylinders.

    The chances of two or more cylinders all going bad by the same amount at the same time in a 2 stroke are about zero.

    That is why the ONLY thing that is important is that you measure the same (+/- 10%) psi in all cylinders.

    This is true only of 2 strokes. Multi-cylinder 2 strokes are essentially multiple engines sharing a crank and flywheel.

  13. #13
    Petty Officer 1st Class 1stgenbird's Avatar
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    Default Re: '57 Lightwin Compression Specs

    I did a thorough re-read of the Evinrude factory service manual and no specs are given nor are any psi numbers mentioned. I will install the head and see what I get. Thanks to all that responded and provided helpful info.

  14. #14
    Vice Admiral 1946Zephyr's Avatar
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    Default Re: '57 Lightwin Compression Specs

    I got 60 on both holes with a JW I had and it was in top shape. You're not going to get much, these pistons are only 1 9/16" in diameter.

    Do what cajuncook1 says about the sea foam. Cleaning the rings and grooves out will get your rings working good and your numbers will max out.
    Vice Admiral Zephyr

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  15. #15
    Petty Officer 1st Class 1stgenbird's Avatar
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    Default Re: '57 Lightwin Compression Specs

    Thanks. However, I never said I have a problem with compression. I just wanted to know what the specs were and the thread just went off on it's own into surmising that my motor has poor compression.

  16. #16
    Moderator JB's Avatar
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    Default Re: '57 Lightwin Compression Specs

    Don't worry about it, bird. It is one of those topics where everyone is an expert, based on what some know it all told them.

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