1996 Johnson 150 J150ELEDB Compression

[Richrico]

What would the standard compression readings be for this year motor? Considering its age and understanding that the readings should be within 10% of each other can you give me a baseline to start with? Thank You.

 

[kevinj]

I just tested mine this spring and I think it was right 100 PSI on a non-certified, non-calibrated compression gauge. I'll have to look up the exact the numbers tonight. These engines had relatively low compression so don't be alarmed if you're not getting 120+ numbers.

KJ

 

[Boobie]

On these motors if you get 100 to 115 on the cylinders don't worry about it. They run fine.

 

[Richrico]

Thanks for the feedback. Hitting in the mid 90 range on first go round. Replacing the thermostat seals and the rubber o rings and cleaning out all the old RTV in the holes. Hopefully the piston rings have not seized up with carbon and will test compression again. I would like to see 100 across the board. Thanks again.

 

[timguy]

Be sure to take compression test with all spark plugs out and a nice fast cranking speed. In some cases, if the motor is in the water, it may be struggling a bit for air......why? A 2 stroke can get it's air from exhaust side as well as intake. What's that mean? When in the water the ability to draw air is restricted because of exhaust discharge being directed below water for obvious reasons. When someone is cranking the motor, the throttle butterfly is normally closed. So in order to provide ample air for cylinder compression, you can wedge the carb cam open a bit with a rag, or something......then do your test. Normally then, you will reach max compression in 4 to 6 revolutions.
Case in point I just had a 1984 Johnson 8 horsepower here for a tune-up. I was getting low compression readings and taking 7,8,9 revolutions to achieve max compression. Then I wedged open the carb butterfly and retested. The result was full compression in five revolutions and almost 100 PSI. What did I decide? Immediately removed power head and found the exhaust tube almost completely choked off with carbon and only a pencil sized hole allowing exhaust to escape. There ya go!