Proper Method for Compression Check

[Codedog]

Just to make sure I don't do anything to "injure" a motor, what is the proper method to run a compression check on a 2-stroke boat motor. I will be checking a few prospective motors this weekend but don't want to cause a problem. <br /><br />I have much experience with checking car/truck engines, but not boats. <br /><br />Throttle open or closed? I know a spray of oil will improve compression/mask problems. Is it OK to do this check dry? How long to crank motor? All plugs out or only the one being checked out?<br /><br />Thanks again!

 

[petryshyn]

Re: Proper Method for Compression Check

>run engine until warm<br />>remove all plugs and disable ignition<br />>wide open throttle<br />>5 - 7 hits per cylinder (same number of hits per cylinder)<br />

 

[rolmops]

Re: Proper Method for Compression Check

Hello.<br />Make sure the seller does not run the engine with a 1:16 or 1:24 mixture (The exhaust will be smoking more than it should)because a larger amount of oil in the mixture tends to increase the compression a bit (less leakage along the rings)and this may be crucial in seeing the difference in compression between the two cylinders which is really the most important piece of information that you want.And do run the engine whith water running through its cooling system.<br />good luck.