300 XS possible coil issue

[swaddict]

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.

[fishnfireman]

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..

[BobB2]

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.

[swaddict]

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

[Savage]

Cha ching!

[mikeaugustine]

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.

[EuropeanAM]

Be sure to report back.

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

[swaddict]

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?

[EuropeanAM]

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

[swaddict]

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.

[fishnfireman]

Thanks for the update !!!

[fiddler]

where can i find this service bulletin?

[Savage]

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

[canes1]

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