300 XS possible coil issue

I have a 2007 300 XS SN#1E002970 that is showing signs of a coil issue. No alarms on my Smartcraft gauges, idles fine, but will not get on plane. You push the throttle forward and nothing happens, no misfires or rough running. I searched online and found Mercury Service Bulletin 2008-09, although my specific engine is not list, it is the same part # for the coils, so I used the chart on page 3 that shows the ohm range(s) for testing the ignition coil. On 4 of the six coils I am getting just out of the range for Primary Pin D to Battery Pin E, range is 13000 to 23000 ohm. Coil #5 reading D to E is 12,790 ohm, Coil #3 reading 12,720 ohm, Coil #2 reading 12,850 ohm and Coil #1 reading 12,760 ohm. Did all 4 coils go bad at once or is this an acceptable reading considering they are close to the 13000 ohm minimum? Or am I heading in the wrong direction? If 4 of the 6 are bad, should I replace all? All help is greatly appreciated.

Lots of issues with those early coils... My 2008 was within the bulletin --- I replaced two before finding out about the bulletin --
Got Merc. to replace them all...
My suggestion would be to replace all Or at least carry a spare---It will sure ruin a good trip..

I cannot address your Ohm variances, but according to bulletin, if one is bad replace all.
My 300XS a bit older than yours (1875) lost a coil under warranty in 2009 and then multiple coils thereafter (out of warranty) as we replaced the bad one,one at a time. ( we would replace one, another would fail) Mercury would not replace mine, so I Finally replaced all as a unit last summer> Runs great now. 200 Hrs, no further problems.

ordered (7) new coils, one for a spare. I will update after the coils have been installed

Cha ching!

I have a 2009 250 Pro XS that fell inside the S/N's for the service bulletin. Merc and my dealership I bought the boat from were no help, so I ended up ordering all six of the "improved" coils. I have smartcraft gauges, and tested the coils at idle and had same issues you were having. In the end after replacing all 6 the boat never ran better, and I have the peace of mind that I don't have any of the crappy ones that Merc should have replaced a long time ago. Good luck, but for me it was worth the cost to know my coils weren't "faulty" or "inferior"...... Bad soldering in coil packs is a very poor excuse for a motor that costs this much, but it is what it is.

Be sure to report back.

For others reading.... a SPARK TEST is a good starting point when suspecting a coil problem. :wink:

Update, new coils came in and installed. I definitely had a coil down. I had installed new plugs 2 trips prior to my loss of power. When pulling the plugs, one was clean and damp with fuel. The others had a lot of carbon building up, I'm assuming from the amount of idling I had to do to get back to the ramp. I cleaned and gapped the plugs at .044. I will test run this week. I'm assuming the plugs are still good or should I purchase a new set?

You'll know within about 5 minutes when you splash-test it. "Probably" ok... but results vary.

Took it out today and engine ran strong with the current plugs. I did order a second set of plugs for the next time. Thanks for the input.

:thumb up2: Thanks for the update !!!

where can i find this service bulletin?

At your local Mercury Dealer........

my 2012 250 pro xs had coil problems around 400hrs. replaced one and then 50 hrs later another. Merc stepped up and replaced all 6 under warranty. so far no problems