Blowing 20amp ignition coil fuse on a 200 efi 3.0 serial number 0T944663

[Jesse welter]

serial number 0T944663

I keep blowing my 20amp ignition fuse on my 2004 200 efi 3.0. It was vary hit and miss last year
only blowing once every 2 weeks now blowing every time I’m on the water. This all started when I
switched to bigger batteries and new charger. Everything is tight and wires look fine. Also it only happens
when at a idol In The water runs great on muffs no issues. Any help or just pointing me in the right
direction would be great. My temp alarm also starts going off for a little bit after fuse blows not sure that has anything to do with it.

thank you
jesse

[JOE54]

test each coil as per serv manual , you can heat them with a hair dryer sometimes to find shorted coil , also look for potting leaking from coils can indicate bad coil

[EuropeanAM]

WHAT SPARK PLUGS are you running? VERY important question!

[Jesse welter]

I’m currently running NGKs BR8HS.

[JOE54]

QL77CC are recomended plug for your engine

[Jesse welter]

Joe could the plugs I have in there currently cause problems like what I’m having?

[Savage]

You really need to use the Champs. The Champs are not to be substituted for any reason according the Mercury

[EuropeanAM]

I have PERSONALLY observed the wrong spark plugs blow this fuse, not once but TWICE.

Use ONLY the recommended QL77CC plugs, and if you still have a problem after that... we're here to help.

[Jesse welter]

Also would a deep cycle 27 group battery have anything to do with it?
the old batteries are group 34 cranking with more cca then my new batteries.

[EuropeanAM]

Possibly if they're weak or discharged- but it's been my experience to ALWAYS address the blatantly obvious problem FIRST, before hunting for "casper" and his cousins.

[Jesse welter]

After 4 days of running fine the 20amp ignition coil fuse blew again
battery's are good and connection are good and new spark plugs. Any other things I can look for or try??

[EuropeanAM]

Sorry for the broken record- but "new spark plugs": Are these CHAMPION, QL77CC spark plugs?

[Jesse welter]

Correct. I thought I had the problem nailed. I had the boat out 4 times the last 2 week
with no issues. It will still crank after fuse blows just no spark on any 6 of the cylinders. I did re rig the boat with 4 new graphs
not sure if the rigging has anything to do with it?

[EuropeanAM]

You may actually have a bad ignition coil, or coil harness. Inspect the electrical connectors and plugs for each coil very carefully (good starting point).

[Jesse welter]

Is there a goood way to test each coil??

[EuropeanAM]

Yes- coil tests are outlined in the Repair Manual, as well as Service Bulletin 2007-25

First step, as suggested, is to inspect the connectors, and each ignition coil VISIBLY. Might even unbolt each one for inspection.

[Jesse welter]

Sounds good. I appreciate all the help and answering all my questions.