Problems after sensor fail 08' optimax 250hp Part 2

[aby n]

Motor details - s/n: 1B547028 MERCURY 250DFI L PROXS

So finally got my buddies boat out on the water after replacing the fuel filter & adding fresh gas ( 5 gallons ) with a double dose of lucas fuel injector cleaner.

Boat was lazy to get on plane, no misfire, top speed of 43mph, ranger 520abc?

the only time the motor sounded odd, was after putting the motor into gear - barely applying throttle. it didnt misfire, but there was no fury or anger coming from the motor... just weak & kinda struggling.

anyways, after burning fuel, numerous stopping, getting back onto plane, all improved but is still lacking top speed at = 56 mph.

following day did a cold compression test, he brought the boat to my house with tools, 5 @ 90psi, 1 @ 85 psi. by the 3rd revolution the psi was achieved.

upon this inspection i noticed some oozing out of coil #3

So i asked a buddy who has a merc manual & he sent me some images on how to pin-out / test the coils.

besides going thru the ohm procedure, is there another way to test the 5 remaining coils?

here is the link to the original thread / inquiry https://www.bbcboards.net/showthread.php?t=1198419

Thanks & have a wonderful new year!

cracked coil.jpgcoil pin out_1.jpgcoil pin out_2.jpg

[angle iron]

I would replace that

[aby n]

^ For sure angle iron.

[Bryanmc57]

besides going thru the ohm procedure, is there another way to test the 5 remaining coils?

You could use a spark tester, but the easiest way is to replace the known bad coil and see if the motor performs as it should. If not dig deeper, if yes go fishing.

[DewRonInc]

Replace bad coil for sure, material coming out is a shorted coil, replace asap

[DewRonInc]

Could damage a PCM

[JOE54]

Could damage a PCM

+1 and may need a new plug on that cyl fouled from no spark

[aby n]

Here are the coil ohm results i observed with my trusty DMM.

5 of 6 coil post's that go into the spark plug wires were corroded/oxidized BIG TIME!

Is there a preferred dielectric grease for marine use/mercury? all post's were dry & cyl 6 was absolutely the worst / lots of dust-oxidation.

Time for some new spark plug wires & ngk IZFR6J's... in addition to a new coil.

coil ohm_010123.jpg

[JOE54]

agree

[EuropeanAM]

They originally used Special Lube 101 in the plug wire boots.

No longer offered by Mercury- but you can use most any dielectric grease.

[aby n]

just updating, so my buddy finally got around to buying a new coil, new plugs, plug wires & some dialtectric grease.

gapped the plugs to ~0.042", got the old coil nipples clean/free of corrosion, indexed the spark plugs, lubed up the nipples & spark plug ends, installed everything.

Boat got up on pad really quick & strong, my buddy said the motor regained the "angry" sound when giving her the berries when taking off.

Ran another strong dose of fuel injector cleaner too.

Once she was warmed up, immediately hit 60mph, after circulating some fuel thru the fuel system, he said it was easy to achieve 64mph.

fyi, this motor started up easy & never misfired prior to the latest round of parts thrown at it. so this is really just sharing my experience with my buddies boat to help others with their motor if you encounter similar issue.

[Bryanmc57]

Always like a happy ending. FYI, Mercury motors do not require the spark plugs to be indexed. That's an OMC thing.

[EuropeanAM]

^^^^ (More specifically, a "Rude" thing).