The coils look good, the wiring all looks good. Is there a good way to test these without firing up the motor?
The coils look good, the wiring all looks good. Is there a good way to test these without firing up the motor?
There are a series of resistance tests (in the Factory Repair Manual) that can be performed. Most diagnostic tools also have an ignition test (or an Auto Self Test, plugs OUT of cylinder head) that permits you to live-test the components.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Got fuel system all put back together. Searched high and low for any visible electrical problems and found nothing. Looked at my blown fuse again and realized i was wrong before. It was the ignition coil fuse (red/yellow).
Tester showed a short to ground at that fuse location, so i started unplugging coils. Always the last place u look. Top coil was causing the short.
Anything else i should look for before replacing that coil?
I noticed 3 different part numbers on the coils, makes me think this isnt the first one to blow. Might pick up an extra one.
Last edited by Sheperd80; 02-07-2022 at 09:26 PM.
1. Inspect the connector for that coil for any signs of melting, distortion, etc.
2. Unplug the connector at the TOP of the coil plate and inspect for any signs of melting, distortion, etc.
3. Replace with OEM Mercury/Quicksilver coil ONLY. There is only ONE (1) current part number for the correct coil, like many parts... new versions or part numbers come out and replace previous part numbers (ie: the old numbers become obsolete).
4. Current part number is: 8M0077471
5. Mercury Service Bulletin 2009-026 recommends that ALL SIX coils be replaced when servicing an engine that experiences a coil failure (in this serial number range). While there are good reasons for this recommendation- the immediate problem would be rectified by replacing the one (failed/shorted) coil. **
** Keep in mind that there is a potential for a shorted coil to damage the PCM's EST circuitry, and also that a blown fuse such as you experienced results in a total loss of propulsion (and control).
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
ive thrown away a 55 gal drum of good looking coils that were badOriginally Posted by Sheperd80
.................................................. ...the scariest thing in life is the unknown ...................................
The plug for the bad coil looks good.
Part of the woven shielding around wires to the plug at top of the coil plate is melted. I pulled it back some and inspected the wires. They dont appear to have melted or been damaged.
I would assume this happened from an overheat or some other failure in the past but once i get it running ill be sure to watch that area for excessive heat. Will also watch closely for any arcing in all the wiring, and of course any fuel leaks at the new connections before taking the boat back to the water.
All the coil plugs have what looks like dieletric grease (white pastey stuff) inside of them. Recommend using some when installing the new coil?
Joe that sounds expensive... It makes me a little nervous thinking that at any time a coil could fail while on plane...
its all a gamble think about that lil seal on top of your HP fuel pump one lil split and bang your dead in the water , i have replace one coil on hundreds of mtrs and not had another fail
.................................................. ...the scariest thing in life is the unknown ...................................
The woven shielding on the coil harness was INTENTIONALLY heated during manufacture. No concern with that.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
We have lift off!
Fired up, runs good.
When the sun goes down ill let her idle and watch for any arcing. Hopefully friday i can get her on the water for a slow test drive, give it a chance to fail, then come home and check for any signs of fuel leaks.
If all goes well, sunday ill be pre-prespawn fishing. Should see water temps near 60.
Thank you everyone for all the input. Couldnt have done it without you guys.
Don i buy parts local whenever possible but any online orders will be going to you.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
.................................................. ...the scariest thing in life is the unknown ...................................
Took her out yesterday and the sputtering in gear idle still exists. Otherwise boat runs fine.
I never did check the plugs. And while i did replace the shorted coil, im wondering if theres another bad one that just isnt shorting to ground.
From Don's post.
5. Mercury Service Bulletin 2009-026 recommends that ALL SIX coils be replaced when servicing an engine that experiences a coil failure (in this serial number range). While there are good reasons for this recommendation- the immediate problem would be rectified by replacing the one (failed/shorted) coil. **
Last edited by Another Distraction; 02-12-2022 at 07:48 AM.
2022 mercury 250HP
s/n 3B216469
0 hrs.
Smart craft gauges
Yeah i know, im reluctant to drop $800 on new coils if i dont have to. If it comes to that then so be it, but im going to continue working through systems and looking for small problems.
Found that all plugs were gapped incorrectly. They were all set to .025 inches while my manual calls for .032 so i regapped and torqued them. Also lightly cleaned them with a brass brush. They werent bad but there was some black build-up that i carefully brushed off of the precious metal node. Sellers notes indicate new plugs last year. Back on the water today and we'll see how it goes. ����
Next step will be a spark test, and coil resistance to see if there are anomalies. If i find 1 or 2 or out of spec ill probably just replace them all. I havent been able to find any wiring issues.
connect a timming light to each plug wire observe flash pattern or not flash dont mistake bad coil for bad plug
.................................................. ...the scariest thing in life is the unknown ...................................
Check the spark plug and wire under the bad coil. See if the plug is black. I would pull all the plugs off and compare. When was the last time you changed out your spark plug wires? Arching wires will cause a misfire as well. Have you ever had the motor full throttle ( dont do it now )? If you have, were you able to run max RPM (again, don't do this until you repair the problem)?
Incidentally, I found my last bad coil using this tester, on each coil one at a time. Lisle 20700 Coil-on Plug Spark Tester
The resistance testing per the manual turned out fine for all 6 coils. When I used the Lisle on all six, I noticed the one coil would not jump the 0.625" gap that I set every few sparks.
The coil can be bad and be very obvious such as a blown 20 amp fuse, coil discoloration, white puffy stuff coming out of a crack in the coil or it will look perfectly fine yet it is weak or intermittent.
In any case you need to find out which cylinder(s) is causing the misfire at idle. If you have ruled out fuel, then all you have left is spark. Another coil, wire or plug, other electrical is your only other choices I would think at this point.
Pull the plugs and send pictures but stay organized and label which plug and wire came from what cylinder so you can diagnose properly.
1B737378 / 2009 - 250 PRO XS
Ok i will do that. When regapping the plugs they were all a little black. But ill check and take pics of all and do a spark test. And yes when i first got the boat (1 month ago) i ran it up to i think 5800 rpm.
In other news...
Boat died and wouldnt restart on the water today. Wouldnt turn over at all so i started checking fuses, nothing. Gave the bulb a squeeze to try again, fuel started shooting out of the water/fuel sensor... wax blob was totally blown out.
When removing it it basically collapsed. The plastic nut was too weak for how tight it was in. Carefully spun it out with various tools and found the threads inside the vst slightly damaged...
My relationship with this motor is off to a rough start... what are the odds that each trip to the lake leads to a new problem?? Is this somehow related to my other issues??
I feel like im playing whack a mole...
Last edited by Sheperd80; 02-13-2022 at 08:40 PM.
It would be good to have the history of maintenance on this motor so we can see what is about to break and what was replaced. Can you get some history from the prior owner?
1B737378 / 2009 - 250 PRO XS
Before you go any further- get yourself a new set of plugs, and gap them at .043-.044" gap (which is the CORRECT gap for YOUR serial number). Gap was updated on these multi-strike ignition coil models to improve idle quality.
See the FAQ Section info for the most up-to-date info on specs such as this.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
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