250 Pro XS - Down on Power

[AML Survivor]

Long time BBC reader, first time posting.

I purchased a new boat this spring. It has a 2009 250 Pro XS (now with 44 hours).

It has ran great until last week. I was in a tournament, blasted off, running strong (5600 RPMs), suddenly it losses power. Got down to 43 mph - throttle wide open - I have forgotten what the RPMs got down to. That went on for 10 minutes or so, then suddenly - like a switch was flipped - the boat took off and ran strong the rest of the day.

I went out today, the motor was running strong, then suddenly, the motor goes down on power. I stopped, nothing was tangled around the prop shaft/lower unit, no warning beeps, no lose plug wires, nothing was smoking and there was a steady stream of water peeing out. Everything appeared normal. Go to get back on plane, probably took a half mile before I got on plane. The motor topped out according to Smartcraft at 5080 RPMs (wide open - but it took a long time to get there), 123 temp, 14 volts, 9 psi.

Power was so sluggish, I couldn't drive the boat onto the trailer. What's up with my baby? Thank you for any advice.

[JAZII]

COIL GOING SOUTH


JAZII

[Phoenix Jim]

yep, get use to it, standard problem on these mercs - been there done that and will be there again

[BADAZZTRITON]

How much do these coils actually cost ?? You know i had a yamaha before this mercury and Yamaha had an issue with their oil pump and did a worldwide recall on them. What is Mercury's problem with these coils, why cant they get something going with getting them replaced ?? Surely there has to be a batch number, build date or something that can distinguish bad ones right ????

[EuropeanAM]

Suggestion:

Utilizing a timing light, check for spark at each spark plug wire (while the engine is down on power.... this sounds like an intermittent issue).

This is the simplest way to determine "which" coil (if any) are not firing.

Coils are covered under warranty, for the duration of the warranty.

The 339-879984T00 coil (coil without plug wire) is approximately $117 with BBC discount.

[AML Survivor]

I just spoke to the mechanic. He asked me to come drive the boat because he can not find a problem. My question is:

If it is a coil issue, isn't that an electrical issue and not related to temperature? I hope the boat performs just like it was when I last used it, when it was so sluggish I could not drive it on to the trailer. In other words, I hope it doesn't jump on plane run like a thoroughbred just because it's cool?

Trying to stay positive. Thanks for any advice.

[EuropeanAM]

Yes, a coil is an electrical issue.... but their "internal circuitry" (as with most any electrical device) can be affected by temperature.

[bigwurm]

Guranteed a coil.. I went thru the same thing. Boat ran 5700 rpm the day before and only 4400 the next morning... I took it to my dealer and they tested each cylinder and found it to be cyclinder #5. Took a coil off another new boat on the lot and fixed it on the spot.. Had a tournamant the next day... That dealer was C &O Marine in Gallatin, TN. They are awesome..

[AML Survivor]

Thank you for the comments.

I am printing this email trail and taking it to the mechanic in the morning. I will report back in case others run into similar problems in the future. Thanks guys.

[sethv]

Yep, coil. When my first one went, it was intermittent for the first 10 miles on the ride home. Then it finally bit the dust for good and was easy to find with the timing light.

I wish there was an easy way to monitor temperature on each coil. I bet you could detect a failure before it happens as internal temperature builds.

[EuropeanAM]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sethv &raquo;</TD></TR><TR><TD CLASS="quote">I wish there was an easy way to monitor temperature on each coil. I bet you could detect a failure before it happens as internal temperature builds.</TD></TR></TABLE>

Interesting thought.... however, I've found that's it's usually "external temperature" (temperature increases from engine running) that seems to induce "intermittent failures". Often have to heat "hard to find intermittent failing coils" with a heat gun to replicate the issue.

[AML Survivor]

Took the mechanic out for a boat ride this morning. He had his computer hooked up to the motor and .... it ran like a thoroughbred, 5800 rpms in no time flat. No "faults" were recorded and no faults were recorded prior to taking it to the water. It ran great the whole time he was with me.

After riding around for a while, I take him back to his shop and go fishing for the rest of the day. The motor ran fine until 5:45pm and like a switch was turned, the motor lost power. I try to call his shop and get a voicemail recording saying they close at 5:30pm.

If it is a coil failing, shouldn't there be a "fault" recorded? I think it's time for the heat gun trick.

[JAZII]

No fault, unless it is shorted or open at key up.

Have the dealer do the spark tests that Don uses, with heat added to each coil with a heat gun.

JAZII

[EuropeanAM]

I've had the best luck (about 90% success rate finding "intermittent coils") by:

-Running a CDS "Auto Self Test- Plugs OUT OF CYLINDER HEAD" (this cycles the coils much like would occur at higher RPM and you can watch the spark occur on a spark tester, live on all six cylinders)

-Repeat test at varying temperatures (heat lamp or heat gun to heat the coils).

-Often best done after running engine in direct sunlight.... let it sit with the hood off in direct sunlight for a period of time, then repeat.

[eagle777]

hi don, since it looks like bout 50/50 on having coils go out at different times, would you have a idea of whats making them go out on 50 percent of the 250 proxs. seems to me if we get that problem fixed we can join the good 50 and stop having fishing trips ruined....thks jack

[AML Survivor]

I put the boat in the water first thing this morning and it ran like a dog.

So, off I went to visit the mechanics again. After listening to a few more of their "bad gas" theories, I said time-out fellas. I pulled out this email trail and read everyone's posts.

They half rolled their eyes, and first pulled the plugs and all they looked good. Next, they hooked some kind of electrical tester device to see if each coil was completing a circuit...? I may have butchered that description but the end result was.... bad #5 coil. They pulled it and sure enough a spot, a blip, a leak, a small blemish was noticeable. They put on a new coil, tested it, it worked right. Put the boat in the water and the motor was back to running like a thoroughbred!

Thank you to all for your comments. This "Board" is always very educational, but today it was also persuasive and naturally, correct.

Sorry for rambling.

[ssimpala71]

FYI, if it happens again and you "catch" it while acting up, You can pull the plugs and "take a read" of them and see one wetter than the others--thats your bad coil!

[EuropeanAM]

Glad to hear you got it fixed!

This particular type of failure (intermittent) can be one of the most difficult to find... and it's always great when you can say "the adventure is over".