1995 30 hp Merc ignition problem

Over the years I've got a lot of help from the guys on the Johnson/Evenrude forum for my boat but I have never posted on this forum. So let me introduce myself, I'm Mike. My son called me last night and was having problems with his 30hp tiller model Mercury. I went over and discovered he was getting no spark to either spark plug. After checking the kill switch and on/off switch I started checking and cleaning connections. By accident I hit the starter with the top ignition coil unplugged and it fired up and ran on the bottom cylendar. When I plugged the connection going to the top ignition coil back in she shut off and was once again getting no spark to either plug. Anybody know what might be causing this?

Re: 1995 30 hp Merc ignition problem

I brought this back to the top to give a little better explaination and to see if anybody had any ideas. <br /><br />It makes no sense to me that with everything connected as it should be I get no spark but if I disconect the top ignition coil I get spark to the lower cylendar. Any ideas?

Re: 1995 30 hp Merc ignition problem

If a CDM unit is bad on any cyl. it can kill all of the cyls. Nice deal huh! that could be your trouble.

Re: 1995 30 hp Merc ignition problem

try to switch the coils and leave the bottom one unpluged this time if the top fires your coil is bad and grounding out causing none of them to work

Re: 1995 30 hp Merc ignition problem

Thanks that was it.....By the way what is the difference between a CDM unit and an ignition coil.... besides the cost LOL had to add that or someone would surley answer about $50

Re: 1995 30 hp Merc ignition problem

The CDM unit has it's portion of the switch box built into it