how to check compression on my merc

[jdmjunkiemonkie]

i was just wondering how would i go about testing compression on my 1997 merc 50 2 stroke.

i know how to test compression on a regular vehicle, is it the same or is it different. if it is different can someone tell me how to do so.

also what should the compression read?

 

[oldman570]

Re: how to check compression on my merc

Compression test is basicaly the same. A reading of 100 with no more that 10 Lbs. diffrance between cylenders should be good. Readings will differ at times if the test is run while it is cold and when it is warmed up. Best is with motor warm ,WOT, all plugs removed, motor turned over atleast 3 times, kill switch pulled to prevent any spark, and the prop removed so you will not get hit by a spinning prop while testing. Readings below 100 as long as they are close can be a ware indication of the rings, piston, and cylender, and the motor still run ,but not up to par for the motor. JMO
Oldman570

 

[JB]

Re: how to check compression on my merc

Look here, JDM:

http://forums.iboats.com/johnson-ev...ion-test-jb-313963.html?highlight=compression

 

[quicktach]

Re: how to check compression on my merc

Basically the same. Pull all plugs and ground. Stop/Run switch on stop. Disconnect fuel. You want it just turned over 3-5 cycles. 100+ psig per cylinder - difference about 10% is good. Get a good readable gauge, one with a pressure release valve is good....