# 1996 evinrude ocean pro 150 compression



## Fishing flip (Jun 16, 2012)

i have a 1996 ocean pro 150 and i was wondering what the compression should be at. mine read 70-75psi in all cylinders is that normal


----------



## TheCaptKen (Mar 14, 2011)

OK, before someone drops in here and starts the, that's too low and the engine is bad. Compression is relative to cranking speed. Those looper engines are slow turning engines anyway and will also register lower unless you really have a hot battery and the starter is in good shape. Also all compression guages are not created equal. My regular shop compression guage us usually 15-20 pounds low when compared to my high dollar Yamaha guages. Bottom line, being your compression is that close in all cylinders, you are good.


----------



## Fishing flip (Jun 16, 2012)

thanx


----------



## Fishing flip (Jun 16, 2012)

TheCaptKen said:


> OK, before someone drops in here and starts the, that's too low and the engine is bad. Compression is relative to cranking speed. Those looper engines are slow turning engines anyway and will also register lower unless you really have a hot battery and the starter is in good shape. Also all compression guages are not created equal. My regular shop compression guage us usually 15-20 pounds low when compared to my high dollar Yamaha guages. Bottom line, being your compression is that close in all cylinders, you are good.


should i try useing another gauge and see if it differs in psi


----------



## SHO-NUFF (May 30, 2011)

The question is the problem you are having. Is it a performance issue? 
Or looking to buy a used engine? As CaptKen said, the OMC looper engines turn really slow during cranking speeds. You need to have all of the spark plugs out of the engine to get it to turn as many RPM's as possible when testing. 
The static compression specs you will find listed in repair manuals are under ideal conditions as far as cranking RPM's and "new" engine specs. A compression test is only good as the quality of compression gauge being used, and cranking speed, so the numbers can be irrelevant. 
The important issue is cylinder balance, or all the cylinders being close to the same PSI during the test. Within 10 to 15 pounds of each other. It is very rare, that all cylinders will have low compression, and well below the said specs at the same time. So, a compression gauge is basically just a tool to isolate one cylinder with a low number due to ring or gasket failure, not a measure of engine performance or longevity. 

The proper procedure is a cylinder leak down test, where air is injected into each cylinder, at a known PSI, and a known amount of time to measure piston ring seal efficiency.

If the engine is running fine, I would careless what the static compression numbers were. 75 lbs at cranking speed equal what PSI at 3000 rpms??


----------

