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Compression on 1962 Johnson FD-16

OkieFromMuskogee

OkieFromMuskogee

New member
Does anyone know what the compression should be for each cylinder on my 1962 Johnson 2-stroke FD-16? I got a reading of 50 psi on the bottom cylinder and 55 on the top. I'm assuming it should be around 100 psi on each. If compression is low on both, should I be thinking rings or a cracked head? Thanks.
 
Remove bypass covers and inspect pistons / rings.----Have never seen a cracked cylinder head to cause low compression.
 
I'm assuming the test I did was correct minus not being able to warm it up. I cant get it started in order to warm it up. I pulled both spark plugs and attached my compression tester to the bottom spark plug hole and pulled 5 times and repeated for the top hole.
 
Remove bypass covers and inspect pistons / rings.----Then depending on what you see you determine the next step to take.-
 
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Just found this..........

Garrys%20OMC%20Compression%20Numbers_zpsvb9svbe2.jpg
 
Like racerone said, you'll have to have a look at the cylinders, rings, pistons to get an idea why your compression is low. You can pull the head first to get a view from the top, but again as racerone said you'll have to remove the bypass covers to see the rings and more of the pistons/cylinders.
 
Do you have access to another compression gauge? Compression should build to max in 5 to 6 swift pulls. When did the problem start? It should run with even 60 psi, but poor idle and low power. My opinion is that 120/130 psi on this motor is only in a "perfect world". In my 50 plus years of twisting wrenches, I have never seen those high compression numbers on this motor. Have had the compression tester for 45 years....know it well and tested it against others.
 
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