2004, 150 Optimax / SN - OT946111 & OT973175 Plug Gap

[Pecos23]

So, i called Mercury Customer Service to confirm the plug gap for my NGK, Lazer Iridium Plugs, IZFR5G.
Mercury gave me the Plug Number IZRF5G-11 as the proper plug and the gap of 1.1mm or .043".

This is completely different from my notes in my shop manual that says the gap for the IZFR5G is supposed to be 1mm or .040" and was changed from .031".
So, what is the proper plug and gap for my motors?
How can this be so difficult?
It's just plugs.

Any help is appreciated.
And yes, i did look on the Sticky Note for FAQ on Mercury Plugs. How can the factory be mistaken?

David
Lake Erie

[leonreno]

Read the faq at the top of forum, there is a link in there for all the spark plugs and gaps for Optimax motors.

[flashman252]

Following closely.... just changed my plugs and ensured gap was 0.32-0.33 on all plugs that was recommended from FAQ sticky. Interesting to note that when i replaced my plugs, half were 0.40-0.45 and half were still 0.31-0.33.

[Pecos23]

Following closely.... just changed my plugs and ensured gap was 0.31 on all plugs that was recommended from FAQ sticky. Interesting to note that when i replaced my plugs, half were 0.40-0.45 and half were still 0.31-0.33.

So, I called back to mercury and voiced my concern over the mixed info on plugs and plug gaps for my motor. The customer service lady took my info and promised to get me an answer.
Here is the reply. Interesting that this info directly from mercury differs from the FAQ sticky note, at least as far as I can understand. The info in the sticky says .032”-.033”
So I am confused. Which is it and where does this come from.
Help!


FROM MERCURY:
Dear David:
Thank you for your e-mail regarding your Mercury engine, serial #0T949111 . We appreciate the opportunity to respond to your concerns. When checking on the spark plugs, you can use either of them, IZFR5G OR 1ZFR5G-11. Both use the same gap, .043.
We hope this information is helpful to you. Should you have any further questions or concerns, please contact our Customer Service department at 920-929-5040 between the hours of 7:00 am and 4:30 pm, Monday through Friday, CST.
Sincerely,
Mercury Outboard Customer Assistance
Ref.# 2020-202346

**This email address is not monitored for replies.**
Please do not reply to this email. Should you need further email contact, please go through our website under the 'contact us' heading.

[leonreno]

The faq was written by Don (European Marine), he is a Mercury Dealer and Mercury Master technician, though that still doesn’t stop the confusion, I think the confusion is there was a change in the gap recommendation after the motor was in service.

[flashman252]

Pecos, I can tell you, I replaced all 6 plugs and ordered 3 spare, because you never know when one might go bad or may receive a bad one with a crack in the porcelain etc. I ordered the IZFR5G plugs and all of them came gapped at 0.31-0.32. They do not come gapped at 0.43 like the email states from mercury. So if you go that route, you will have to add gap to the plugs. I am not saying you are being told wrong from mercury but just so you know about the gapping in these plugs if you order. Just did my plugs 2 weeks ago.

[Pecos23]

I completely Agree with you, but why would mercury do the research and then come back with a different gapping? They actually built the motor, and made the recommended changes to plugs and gaps, so you would assume they know best? Maybe Don can chime in here and add some clarity to the situation, I know I am not the only one.

[flashman252]

Lol, couldn't tell you pecos. I am watching closely. I will say, my motor runs pretty damn good after changing plugs and leaving a gap that is recommended on the FAQ page. My motor is a 2008 though but also a 150 optimax. Hopefully don can help you out and clarify this. Good luck to you.

[Rsylvestri]

Same here although it’s an 04 175 Optimax with IZFR5G gapped at @.032-.033 for 45hrs now after reading the FAQ. Mine runs great through all rpm ranges. Watching this as I’ll do plugs again in a few months.

[SilverFox579]

How can the factory be mistaken?

People make mistakes and some customer service folks aren't, um, "technically savvy".

The information in the FAQ information is CORRECT and continually updated by Don (updated again this month). Standard 2.5L Optimax plug gap is .032 - .033", do not gap at .043". Oh, and always, always, always, verify plug gap using a wire gauge prior to installation.

-IZFR5G (NGK)@ .032-.033" for Standard Opti's 135-225HP

[Pecos23]

Silverfox579
The Mercury customer service rep admitted that there is confusion. She also said she was going to research this and get to the bottom of it from the Mercury Side, admitting that she wasn't technically savvy. I am confident that she has the resources at the Mercury world headquarters to find the proper gap for a sparkplug.
So to say that Don is right, and Mercury is wrong without providing any source for Don's information add even more confusion.
Don's information directly contradicts information from Mercury. How can you be so sure his information is correct, and that Mercury's is wrong.
I only want the best information to protect my motors, but this situation needs to be clarified for the benefit of the group.

[flashman252]

Pecos, have you pulled the plugs in your motor and checked the gap on the plugs you are trying to replace? Curious if the plugs you have in it now are gapped at 0.32-0.33. If the boat worked and ran fine with this gapping, I would replace with that same gap. I can tell you that I could not pull over 4900 RPM at WOT and the boat was dog in regards to holeshot and had 3 plugs gapped at 0.4-0.45. Changing all 6 to the "correct" gap of 0.32-0.33, I gained 5-7 mph top end and seeing 5400 RPM and the idle was way smoother and the holeshot was much much faster. I have not dialed in the boat 100% and have only owned for a little over a month now, so lifting the motor should get me close to the max RPM I am needing to see. Either way, Silver has been a WEALTH of knowledge and when this guy sends information, it has been spot on thus far. Just my 0.02 though, good luck in getting through this frustration. Hope you get it figured out.

[leonreno]

Silverfox579
The Mercury customer service rep admitted that there is confusion. She also said she was going to research this and get to the bottom of it from the Mercury Side, admitting that she wasn't technically savvy. I am confident that she has the resources at the Mercury world headquarters to find the proper gap for a sparkplug.
So to say that Don is right, and Mercury is wrong without providing any source for Don's information add even more confusion.
Don's information directly contradicts information from Mercury. How can you be so sure his information is correct, and that Mercury's is wrong.
I only want the best information to protect my motors, but this situation needs to be clarified for the benefit of the group.

The information Don provides actually comes from Mercury, he is a Mercury Master tech and dealer. I would trust info here as it’s been vetted and most up to date info you will find, I personally would not trust what a customer service rep says over what Don says, which I agree is a shame that the info is not the same. But customer service reps are not technicians, they just answer phones and look up info on a computer. Unfortunately it’s not jiving with this info.

[Pecos23]

Pecos, have you pulled the plugs in your motor and checked the gap on the plugs you are trying to replace? Curious if the plugs you have in it now are gapped at 0.32-0.33. If the boat worked and ran fine with this gapping, I would replace with that same gap. I can tell you that I could not pull over 4900 RPM at WOT and the boat was dog in regards to holeshot and had 3 plugs gapped at 0.4-0.45. Changing all 6 to the "correct" gap of 0.32-0.33, I gained 5-7 mph top end and seeing 5400 RPM and the idle was way smoother and the holeshot was much much faster. I have not dialed in the boat 100% and have only owned for a little over a month now, so lifting the motor should get me close to the max RPM I am needing to see. Either way, Silver has been a WEALTH of knowledge and when this guy sends information, it has been spot on thus far. Just my 0.02 though, good luck in getting through this frustration. Hope you get it figured out.

I have not pulled them to see the gap. I have 12 plugs to pull and gap, so i prefer to do this at my bench instead of at the marina while winterizing. I do remember going through this drill a handful of years ago, and i'm betting they are gapped at .040 since my notes in my manual say that mercury changed this from .031-.033.

[Pecos23]

The information Don provides actually comes from Mercury, he is a Mercury Master tech and dealer. I would trust info here as it’s been vetted and most up to date info you will find, I personally would not trust what a customer service rep says over what Don says, which I agree is a shame that the info is not the same. But customer service reps are not technicians, they just answer phones and look up info on a computer. Unfortunately it’s not jiving with this info.

I don't doubt that Don has current and up to date information. I have utilized his expertise in the past and he has not been wrong yet.
The information i received from Mercury didn't just come from the "customer service rep", but is a product of her research within the walls of Mercury Marine, and confirms my notes.

BBC boards offers different information and many members have stepped in to support Don's recommendations, but without any references or explanations other than Don says so.

I am curious to know why he hasn't jumped on this thread to offer his thoughts? As i would welcome his explanation since it seems to be a confusing topic for many people outside of this tread.
Thanks

[Pecos23]

Here is the Mercury Service Bulletin, 2002-22 that references the plug and gap change for this series of Optimax motors.
It took 4-5 calls to Mercury Marine before i found a guy curious enough to find the proper information. All others gave outdated information.

Mercury Marine Service Bullentin 2002-22, Spark Plug Change.pdf

Service Bulletin 2002-22, Plug and Gap change, Optimax.jpg

[TomP.]

That explains the confusion two different plug types.

[flashman252]

So both are ok then, but the gap is dependent on which plug is put in the motor? Makes sense why motor was so unhappy, they were the IZFR5G plugs and had gaps of 0.4-0.45. No bueno for sure.