Spark plug ?

[abianca99]

This is personally applying to a 2007 225 ProXS. I am curious as to why Mercury RECOMMENDS a spark plug with a preset gapping of .032" (IZFR6J)? I have read here that, sometimes, it is recommended to gap THESE spark plugs further to .040"-.044". This wider gapping MAY help with the idle to slight off idle "roughness/performance" that these engines CAN have. This is where my confusion is. If that spark plug may give better idle performance with say a .044" gap, why isn't that what the spark plugs are pregapped to begin with? OR why doesn't Mercury recommend a spark plug that does not have the possible issues of idle "roughness"? Let's say a spark plug that has all the positive characteristics of the IZFR6J without the possibility of a rough idle. I feel, with the sensitivity of how you need to spread the gap on THESE spark plugs, that it would be much safer and much easier for the consumer to just buy a spark plug that was already pregapped to .044"...to avoid the idle roughness to begin with. Problem solved??? No need to worry about accidentally messing up your newly purchased, not cheap, IZFR6J spark pugs??? So with all that said. Why doesn't Mercury address this slight issue with a more direct resolution? Or do they? Is there a FACTORY PRESET spark plug that does meet the criteria for this engine AND addresses the possible idle issue? If not, is there plans to maybe do so in the future? Lastly, if you gap the IZFR6J to .044", you possibly gain better idle performance. But, are you losing any performance or run quality any where else in the rpm range of this engine? Any input on this is appreciated.

Thank you,
Aaron

[EuropeanAM]

Aaron:

At the factory level, a spark plug is being utilized that indeed IS "pre-gapped" to .044" (in engines that benefit from this gap). It's standard in the 250 ProXS engine.

This plug is not available for purchase outside Mercury, and as of this date, it's not yet available as a "replacement part number" within the Mercury System.

Exact same spark plug, just has a -11 at the end of the plug number, denoting the .044" gap.

Since there's a general expectation that engines are serviced at authorized Mercury Dealers (that's not really that unreasonable of an expectation, given the overall complexity of these engines, and their electronic systems), concerns over spark plug gap are relatively small in the overall scheme of things. Most Certified or Master Technicians are perfectly capable of gapping a spark plug successfully.

As stated many times in various posts on this subject.... the increased gap is authorized to improve idle quality (and that's it's ONLY reason). This is sometimes necessary due to varying fuel QUALITIES across a wide variety of climatatic conditions, over which the manufacturer has NO control. When the engine is manufactured, there is no way for them to know if it will be used in Alaska at temps below ZERO, or in Miami in temps of 115 degrees F. And then the fuels.... that's a whole different scenario.

NO DISCERNABLE DIFFERENCE in top end performance from EITHER gap.

[abianca99]

Don,
Thanks for the info. I do realize that adjusting them isn't very difficult, but more or less unnecessary with the option of a different spark plug(like the IZFR6J-11). I also realize that adjusting a spark plug is small in the whole scheme of things with these engines. That IS why I found it odd that it wasn't really directly addressed. But, I guess it KIND OF has been with the factory install of them in the 250 ProXS. But what does a guy do that wants to change the plugs himself on these engines? Use the standard IZFR6J and gap them? I am assuming that "factory only" means they are only available at the Mercury factory. A dealer cannot purchase them. It just seems odd to me that they have the plug, actually use it, but haven't made available anywhere but the factory.

Thanks,
Aaron

[EuropeanAM]

The -11 plug is indeed used at the factory. At one point.... there was talk of it being made available as a replacement part (but the part number was later superceeded BACK to the IZFR6J).

I agree... it would be nice to get them in the -11 (sure would save me a TON of time).

Until then.... gues we'll both be gapping away.