compression test procedure?

[pataterchip]

Warm engine. Ignition disabled (pull kill switch), remove plugs. Install gauge and spin engine 6 or 8 revs. No oil unless you doing further diagnosis of an apparent issue such as low compression on one cylinder. Numbers should ideally be within 10% of each other and over 100# or whatever your service manual indicates. Throttle needs to be full open on a four stroke motor but it doesn't matter on a two-stroke.

I see lots of posts talking about grounding the spark plug wires, is this necessary and if so how exactly would I ground them the boot on mine don't seem to be removeable? I realize this may sound stupid but I can't afford to screw this up. I need to do a compression test but don't want to ruin the ignition coils.

I have a 2001 mercury 60HP 4 stroke 4cylinder bigfoot S/N# OT 294062P.

 

[Silvertip]

Re: compression test procedure?

Pull the kill switch lanyard. That safely kills the ignition and then there is no need to ground anything.

 

[rtpassini]

Re: compression test procedure?

i have no clue where my kill switch lanyard is...lol.

otherwise use alligator clips

 

[James R]

Re: compression test procedure?

Some motors don't have the kill switches. Two methods.
One.Dont turn the ignition on and jump the starter sol to turn the motor over.
Two. Use a piece of bare copper solid wire, say a piece of 12 or 14 gage household electrical ground wire, and fasten it under a casing bolt, ie under a thermostat bolt, and form loops to take the threaded part of the plugs. Make sure they are tight so that the plugs dont fall out. Then you can use the key to turn the motor over. Also a good way to check if the plugs are firing.