Popping 20 Amp fuse

[blue perch]

S/N 1B972929 2013 Merc Pro XS 250
Good evening. This weekend I was landing the boat and suddenly it died. No sputter or any indication of a problem. Thought we were out of fuel but changed tanks and nothing. It’s cranking but won’t turn over. Got it on the trailer and popped the top. My buddy checked the fuse on the block and the 20 was blown. We replaced it and tried cranking it again, nothing. Checked the new fuse and it was blown. The boat was running great all day. Any insight would be appreciated.
thanks. Jesse

[lpugh]

Post a pic of the fuse block with an indicator of which is blowing, most likely has two 20 amp fuses
take a good visual look all the coils for cracks, deforming or material coming thru the case of the coils
Disconnect all six coil primary connectors and see if it still blows the fuse, reconnect one at a time to identifie which if this is the coil fuse

[EuropeanAM]

Probably a good idea to inspect the coils and coil harness connectors first. Be very careful about replacing the fuse as it is possible to destroy the PCM if you have a shorted ignition coil or harness.

Determine the wire colors that correspond to the blown fuse.

[basspro57]

Probably a good idea to inspect the coils and coil harness connectors first. Be very careful about replacing the fuse as it is possible to destroy the PCM if you have a shorted ignition coil or harness.

Determine the wire colors that correspond to the blown fuse.

Agree with Don...had a few buddies that had this happen and it was a bad coil. You can sometimes visually inspect them and see if one looks molten or oozing stuff out of it. It will also become much hotter than the others with the motor running. If the motor has a lot of hours, you might want to replace them all because it seems like once one goes the rest are soon to follow. As Don said...this is also hard on the PCM so you may not hurt it with this one but the next one might take it out.

[blue perch]

I can’t get it restarted since it died on the lake. I will check the coils but I have a feeling I’ll be taking it in.

[blue perch]

So what is the ballpark cost to replace the whole thing and is it something I could do myself?
thanks.

[Savage]

You don't want to replace all the coils on a 2013 motor, only the defective coil, if it's a coil.

[JOE54]

smell the coils. You will find the bad one.

stank dont they

[Savage]

Coils are NOT "made to run so many hours before failure".
Replacing parts that are not defective is the wrong way to fix something. Replace the bad part and move on.

[blue perch]

There are 487 hours on the motor.

[apdriver]

premature coil failures are quite often caused by lack of maintenance causing the coils to operate constantly at a much higher voltage outputs which can cause insulation breakdown and shorted windings and a lot more heat do to increased current flow

Leon, please expand on this. What lack of maintenance causes this?

[EuropeanAM]

Ok guys- there is a LOT of errant and questionable info being put out in this topic. For that reason- it's going to be cleaned up, don't take it personally.

Observations:

-Mercury doesn't use "Years". So all of the comments about "that year and this year" are merely a generalization.

-Comparisons of coils that were problematic back in the later 2000's to those on an engine that was manufactured on 11/15/2012 are not really relevant.

-There is no reason, other than the ability to spend a lot of money, for someone to replace "all" of the coils on this engine.

-IF it's actually a coil (note that very early on we still don't have a confirmation of this as a fact), replace THAT coil, inspect the connector FOR that coil, if all is good replace the fuse.

While I know that some are trying to help (and that's appreciated), it amazes me that the same folks who will tell folks to cheap out on something critical would be the same ones to recommend replacing "everything".

[lpugh]

premature coil failures are quite often caused by lack of maintenance causing the coils to operate constantly at a much higher voltage outputs which can cause insulation breakdown and shorted windings and a lot more heat do to increased current flow

Leon, please expand on this. What lack of maintenance causes this?

Open ckt plug wires, worn out spark plugs, extreme lean air fuel ratios, all will drive coil voltage very high

[apdriver]

Open ckt plug wires, worn out spark plugs, extreme lean air fuel ratios, all will drive coil voltage very high

Thank you, Sir...

[blue perch]

My plugs have less than 100 hours. I don’t put a lot of time on my boat motor per year because of the no wake rules on the lakes I fish. How often should the plugs be changed?

[blue perch]

7F67671E-07D0-4A06-8739-C735924A6F34.jpegAfter 30 seconds of inspection. This is what I found. Where can I get one that’s not eBay? Part# 8M0042380

[lpugh]

Mercury Parts, Mercury Outboards, Smartcraft & Accessories, European Marine Rhonda and Don will take care of you

[SilverFox579]

My plugs have less than 100 hours. I don’t put a lot of time on my boat motor per year because of the no wake rules on the lakes I fish. How often should the plugs be changed?

Maintenance schedule, and a whole bunch of other very useful information, readily available in the awesome FAQ at top of the forum - Recommended Annual Maintenance or Winterization for Optimax Engines

I second Leon's recommendation to contact Rhonda at European Marine, awesome support.

[basspro57]

Good to see you found the problem. With 487 hours, I would say you probably have an unit that failed a little earlier than the design goal MTBF (you all can search that term if you would like to learn something about how electronic devices are designed for reliability and life expectancy) for the coils. Replace it and see how it goes. If you start to get others failing, then I will again recommend replacing them all. As Don stated, the coil shorting does stress the PCM although the fuse blows. The fuse will blow in 0.1 seconds at 2x the rated current. So the PCM trace is seeing 40A for 0.1 seconds during this shorted coil event before the fuse blows. That does deteriorate the trace in the PCM. Do it too many times and you are spending $1800 for a new PCM. It also depends upon if you are a tournament fisherman (where bad coils could be a big problem) or just a recreational fisherman. Be sure to maintain your motor as the items brought up by Leon are certainly a possibility for early failure. If you haven't had your injectors cleaned and flowed in 487 hours...that needs to be done. Also, you should be following the maintenance (changing the plugs regularly).

[EuropeanAM]

Rhonda can set you up- see her post (pinned at the top of the Forum). BEST methods for ordering are on our website, or by email (using serial number of engine).

Be sure to check the connector for that coil as well.

In regards to the comments that Craig made (above) regarding the "trace"... the PCM actually does not monitor all of the coil circuits. PCM damage occurs when either GROUND or 12V+ power bridges to the EST (driver) circuit. Not all "fuse blowing" events on that fuse (even inside the coil) are due to this particular failure mode, but extreme caution is recommended due to the potential of PCM damage.