Re: '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
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.php?p=2648076#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!!!