how to check compression

[kking]

I know this is a dumb question, but how is the best way to check compression on a XR6 motor. Do I disconnect the kill switch to check it? Thanks

[prepsdk]

Don recommends taking compression numbers ONLY as follows:

-Engine warmed up FULLY
-Fully charged, properly rated battery
-ALL Spark plugs removed
-Kill switch in OFF position
-Plug wires on spark tester (or grounded- an added precaution)
-Throttle plates at WOT (Wide Open Throttle) position

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by prepsdk &raquo;</td></tr><tr><td class="quote">Don recommends taking compression numbers ONLY as follows:

-Engine warmed up FULLY
-Fully charged, properly rated battery
-ALL Spark plugs removed
-Kill switch in OFF position
-Plug wires on spark tester (or grounded- an added precaution)
-Throttle plates at WOT (Wide Open Throttle) position</td></tr></table>

Precisely correct.

[kking]

How do you suggest grounding the wires? Thanks

[Lockon]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by kking &raquo;</td></tr><tr><td class="quote"> How do you suggest grounding the wires? Thanks</td></tr></table>

Don't know if the way I did it is right or wrong....but I took some 10GA wire and stuck it in each spark plug wire then stuck the other end to a bolt on the heads.

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Lockon &raquo;</td></tr><tr><td class="quote">

Don't know if the way I did it is right or wrong....but I took some 10GA wire and stuck it in each spark plug wire then stuck the other end to a bolt on the heads.

</td></tr></table>

That will work.... a Spark Tester is the BEST choice. A set of alligator-clip jumper wires can also be used.

This is a "redundant precaution" of course... but I personally witnessed one scenario where a tech TURNED OFF the lanyard switch in the boat, proceeded to do a compression check, and got one heck of a scare when escaping fuel/air mixture was IGNITED by a nearby spark plug wire (someone thought it would be a good idea to just disconnect the lanyard switch when it failed).

Nice, big (but fortunately short-lived) ball of fire.

[prepsdk]

Would that be one like this:

[EuropeanAM]

Exactly like that.

[kking]

where can I get one like that Don?

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by kking &raquo;</td></tr><tr><td class="quote">where can I get one like that Don?</td></tr></table>

Sherm @ Sherm's Marine (or I) would be more than happy to order you one.

They're available in CDI, or as a Mercury Part Number.

Email or Phone are the BEST means of contacting the Parts Department(s).