Merc 500, 1973, 50HP, compression testing

[cbcrawford]

OK, I'm sure this is out there somewhere already, but I can't seem to master the search function enough to narrow it down to what I'm looking for.<br /><br />I just want to make sure I'm not crazy - My manual says that, to test compression, I pull all the plugs, then GROUND them to the engine? Does this mean that I need to run wire up into the plug wires and tie them off to a ground on my motor?!?!? <br /><br />Next question, it says once the compression tester is in place I turn the motor over at least five compression cycles - do I use the key, or do I need to hook up a pull rope? <br /><br />Thanks is advance for any help here!<br /><br />CC

 

[cbcrawford]

Re: Merc 500, 1973, 50HP, compression testing

oh yeah, and how do I "hold the throttle at WOT" for the test? it won't turn over in gear, will it?<br /><br />CC

 

[NathanY]

Re: Merc 500, 1973, 50HP, compression testing

Does this mean that I need to run wire up into the plug wires and tie them off to a ground on my motor?!?!?

Yes they have to be grounded. <br /><br />

oh yeah, and how do I "hold the throttle at WOT" for the test? it won't turn over in gear, will it?

I just stick a screw driver in the carb to hold the butterfly open, if I even worry about it, which I usually dont. <br /><br />Also it is best to check compression on a warm engine.