Random Miss at Idle. HELP!!

[Hicktacular]

2008 150 Optimax SN: 1B550483 on a 2008 192 Pro Craft Super Pro
Issue:
Random miss/stumble at idle. Really only noticable in gear.

What I have done:
Replaced Compressor. (old one went out)
Replaced fuel line from tank to lift pump.
Sent all 12 injectors and rails to CCMS (great guys) for testing and cleaning.
Replaced plugs. Third set in a year.
Rebuilt lift pump.
Replaced reeds with CCMS. (did not not lap cages. Plan to re-do the reeds and lap cages.)
Drop cylinder test. Unplug each injector, and engine drops. Cleans up when plugged back up.
Pulled each plug wire on muffs, and appears to jump around .5 inches.
Cleaned VSP. Was spotless. Cleaned the pump screens for good measure.
Tested battery. Tests good, but still suspicious.
Replaced TSP.
Replaced fuel filter.
I DO run ethanol gas, but simply because I don't trust the stores in my area that advertise the non ethanol.
I DO use marine Stabil in every tank.
I DO use quickcleen in every tank.
Compression is between 110 to 115 on all cylinders.
Checked fuel/air pressure with tire gauge.. Need to check better. Appeared 90/80 psi Fuel/air at idle.
No Alarms.
Seems to run fine in every stage above idle.
I believe I am over propped. I have a 23P Tempest. Max RPMs are 5200.
Curious if this low RPMs are the root of all of this, or if the problem is causing the low RPMs..
I have not taken it to a shop yet to have it connected and scanned. That probably needs to happen.


I have a video, but have not found out how to post it here...

I have read for hours on this site, and probably tried more things that I have listed. I really appreciate any help.

[06 SB]

This is a thread on a friend of mine’s motor. It was a 3.0L motor so not everything will translate to your motor, but the eventual solution could be. There are some other suggestions in there too.

http://www.bbcboards.net/showthread.php?t=685863&page=2

[SilverFox579]

OP's topic on the Mercury Motors forum for reference - http://www.bbcboards.net/showthread.php?t=1045431

[EuropeanAM]

I would suggest lapping the reed cages FIRST to ensure a good clean seal. The 2.5L Opti's are especially sensitive to leakage (often caused by grit or grime in the intake or inside the cowling). Make sure the lower cowlings, adapter plate and Air Handler are CLEAN (oil is ok, dirt or grit are not).

Also take a careful look at the LOWER set of teeth on the flywheel. Check for any rust, flaky paint, etc. If present- flywheel needs to be wire brushed, primed and repainted (OFF the engine of course).

Also try spraying some soapy water around each of the Direct Injectors at IDLE. Watch for spitting or bubbles (due to leaking o-ring).

Also- confirm what spark plug you are running, and what gap they have been gapped to....

Other possibilities- but those should get you started.

[Hicktacular]

Thanks for the suggestions!!
I am running IZFR5G plugs. I have been gaping them at .032, but read last night that .042 was suggested for a better idle. Is that accurate? Could be the cause if so..
I'll check the flywheel today. If I have any flaky paint on the teeth, I need to pull it and paint it? Not that I doubt you, but can you explain why that is important for my understanding? Also, Any particular paint required?

edit 1: here is a link to a video of the engine stumbling at idle



edit: Attached is a picture of the only tooth that does not look perfect. Is this enough cause to need repainted. I am not sure why this one tooth looks this way, but no rust or any other defect, otherwise.

Thanks!!

flywheel tooth.jpg

[Hicktacular]

Don,

I pulled the reeds out today to lap them. All appear to be in perfect condition. several of them appeared closed, and the ones that were not closed, closed with a light touch of the finger.

I put it back together without lapping the cages. I am afraid that I will make it worse. I suspected that I had one that was broken, but do not. From what I have read from your other posts, the fact that all still look perfect (with out any chipped corners) means that they are sitting flat on the cage, and that is the main thing. I am not saying that your suggestion could not help. I am just saying that it probably is not causing this issue, and I should not risk introducing something else to the equation. I'll post a video of the reed closing.

After this, if you think that the cages are not flat enough for an average fisherman, let me know and I'll pull them out and lap them.

[Hicktacular]

Another view of the reeds.

[JOE54]

do not gap izfr5g plugs at .042, that's for pxs mtrs, my opinion , reeds not your problem, vid almost sounds like loosing voltage to engine or geargase locking for split second

[SilverFox579]

+1 stick to .032" for the plugs!!

You indicated in your original post you thought your battery was marginal, need to make certain it meets (actually exceeds) engine minimum required capacity.

Joe and Don are Optimax "whispers", when they talk I listen.

[Hicktacular]

Thanks guys. I have it in the water today. Seems better with the .042, but still there.. I had the battery tested yesterday. Just over 1000 cca. It is a deka 24M7 and is 2 years old.
I installed a battery disconnect a year or so ago. I put it on the ground side. All of my electronics go through the same disconnect, and show no issues. Should I take it out of the loop to see?

Update: I took the disconnect out of the loop, and did not help..

[Hicktacular]

I also noticed today that it seems worse when the engine gets hot. The idle was pretty good when I first put in this morning.

[EuropeanAM]

A couple observations:

1. As suggested, STICK WITH .032-.033" gap on your plugs. Do NOT gap to .042"

2. Reed gap is WAY over the max standoff. .020" max, measured at the tip of the reed. You're at least double (in some cases triple) the max. This CAN cause idle problems.

3. That one flywheel tooth appears to be CHIPPED. The crank sensor looks at those teeth based on a magnetic field, and sends a signal back to the PCM. The PCM interprets the flywheel position based on the size and patterns of teeth.

Any abnormality in the size of a tooth, a missing tooth, or rusty flaking or flapping paint will cause an abnormal signal as it passes through the magnetic field, essentially confusing the PCM until it sees another pattern it recognizes. Can also sometimes result in hard starting.

4. You may also be fighting a rich running condition, especially since the engine runs well when cold and poorly when warm.

[Hicktacular]

So.. what I am reading is:
1. Lap cages to rule it out.
2. Could be a timing issue.
3. Could still be the battery.
4. Could be running rich.

Today, I ruled out #3 by using a known good battery. Made zero difference.

I can do #1 just to make sure.

#2 is a mystery to me. How do I further diagnose if the tooth is the issue? The idea makes sense, and thanks Don for the explication. Seems the only way to repair would be to replace it?

#4 does make sense, because I seem to burn more fuel than I used to.


Am I missing any suggestions so far? Also, could the fact that it seems to run great above an idle, rule any of these out? Or point to one, more than the other?

[EuropeanAM]

Am I missing any suggestions so far? Also, could the fact that it seems to run great above an idle, rule any of these out? Or point to one, more than the other?

Just the proper plug gap.

Your results point to 1,2 or 4.

You can "see" a potential problem with #2 (NOT a timing issue- at least not in the "adjustable" sense). Really would need to see that tooth in a lot more detail for that one.

#1 can actually contribute to a rich-running condition... or exasperate one that already exists.

[Hicktacular]

I'll try to get a better picture of the tooth. It really looks insignificant to me, but you understand this much more than I do. I am curious what might have hit it. And did it hit the sensor, and maybe mess it up.
We just got word that Alabama is shutting down tomorrow evening. I'll fish tomorrow, and do the reed cages tomorrow evening. I really appreciate the help, and the time you guys put into the forum. Your past posts have helped me understand the majic that goes on under a mercury cowling.

[Hicktacular]

20200403_190026.jpg20200403_190015.jpg20200403_185246.jpg20200403_185015.jpg

[Hicktacular]

It looks like the end of the crank position sensor is worn or broken off. Or do they always look like that. Curious if that could be the issue. I am trying to do some research on how to test them. I don't see anything in the manual. One video I see on line, talks about checking the voltage output of the sensor while cranking over the engine. I did that, and it has 1.308v. I have no idea what it should be though lol. I'll spend the next few hours reading I guess..

[lpugh]

Looks like the sensor may be rubbing the teeth if so, replace it for sure and be sure the air gap is set correctly
Voltage output will vary. greatly depending on rpm, check the air gap when installed, as I recall it should be about .050. 1.3 volts sounds just little on the low side. The only way to really get a good test of these is a lab scope or DSO to analyze the waveform and help spot intermittent, be sure the motor is cranking properly, low crank speed will cause low peak to peak voltage
If you set a timing light beside you when running, if the crank sensor stops, all spark will stop and the light will stop flashing. But that is only one of the many things that could be causing your concerns

[EuropeanAM]

Air gap technically isn't "adjustable" although you can get a very slight movement of the sensor on the two bolts securing it. Try as I might- the best I can say from the photos is "suspect". Something hard interacted with that tooth (and at least one adjacent tooth) at some time in the engine's life.

Crank sensor is probably ok, but given the circumstances and the suspect appearance, I would definitely recommend replacing it.

BTW- you have an OIL LEAK at the top crank seal (there is oil running from under the flywheel).

[Hicktacular]

Thanks for the suggestions guys. I called a local marine place (Freedom Marine) on Guntersville, and they just happened to have the sensor. I got it ($80) and put it on. seems to run a little better, but it may just be me.. The fish were biting good too, so that makes the world a little better place to be in. The new sensor looks completely different on the end. Appears to have about the same air gap. Maybe .030 ish. I'll measure it tomorrow to make sure. Tomorrow after church, I'll check the air gap on the CPS, re-gap the plugs, and MAYBE pull the cages..

Don, What can be done with the flywheel? Can it be repaired? I assume the metal needs filled in with more metal, or is the wire brush, primer and a good smooth coat of paint good enough? Could a shop tell me 100% that the flywheel was the issue if I took the boat to them? (If the reed cages don't help)