Grounding the plugs?

[myelo]

I want to do a compression test on my 72 Merc 65 hp outboard. Im reading everywhere, including my Clymer manual, that you need to ground the plugs. Exactly how do you do this? I check my fuel pump earlier while cranking and didn't do anything but disconnect the leads from the plugs. Did I screw something up doing this? I did get one hell of a spark from the battery connection, but that's all. Thanks in advance for any help/suggestions!

 

[Hooty]

Re: Grounding the plugs?

Leave the ignition switch in the "off" position. Use a jumper wire and jump from the big red (+) cable, from the battery, on the starter solenoid to the small post with (I think) yellow w/red stripe wire. Do not touch the jumper wire to the post with the black wire. That post is ground. When you touch the jumper wire to the small post, that will pull the starter solenoid in and spin the engine without spark. <br /><br />g'luck & c/6<br /><br />Hooty

 

[Boatist]

Re: Grounding the plugs?

Myelo<br />Pretty easy for me but I only have a two cylinder outboard. I remove the plugs then put the plug wire back on. I use a battery charger clip to hook to the plug base and ground the other end of wire with another clip to the head or block. The connectors were cheap. I actually made to ground a plug with a wide gap so can very easy check spark when I suspect a weak spark.

 

[myelo]

Re: Grounding the plugs?

thanks for the info. Can I just pull the kill switch? I thought I read somewhere where you could do that. Also, do I need to remove plugs to ground them, or just pull the wires? I'm pretty visual, so a diagram somewhere would be great. Thanks again!

 

[one more cast]

Re: Grounding the plugs?

Remove ALL the plugs to do a compression check.

 

[Hooty]

Re: Grounding the plugs?

....or you can just pull the kill switch.<br /><br />c/6<br /><br />Hooty