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Author Topic:   Spark Plugs on Low-Emission Engines
jimh posted 02-23-2004 09:25 AM ET (US)   Profile for jimh   Send Email to jimh  
There has been some mention previously about the spark plugs required for use with some low-emission (low-E) outboard engines. I would like to gather some informed opinion and if possible first-hand experience with the maintenance involved in low-E 2-stroke engines and their spark plugs.

With regard to Mercury Optimax, Evinrude Ficht, and Yamaha HPDI engines:

What is the recommended normal maintenance interval for changing spark plugs?

How expensive are the spark plugs?

Are the spark plugs easily sourced or do you have to buy exotic OEM plugs from a dealer?

Do the spark plugs have to be indexed when installed? (Here I refer to the special procedure used when installing a spark plug to align the electrode in the cylinder head in a specific orientation.)

If any of these questions are applicable to a low-emission 4-stroke engine, I would like to hear of those procedures, too.

Sal DiMercurio posted 02-23-2004 11:34 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jim, I can help you on the 2 stroke FICHT engines.
The FICHT plugs should be changed every 75 hours because the ignition is so hot it just eats the plugs.
For instance, i'm told by a very reputable tech friend that the gap recomendation is .030 but it's better to gap .028 because within 40 - 50 hours the plugs will be between .040 & .045 which I find true.
If you buy these plugs from a dealer, your going to pay upwards of $10.00 each, if you order them from NAPA auto supply, you pay under $5.00 each.
Yes, the plugs must be indext or the engine just wont run right, & take it from me, it's true, as i'v found out.
Seems as of now, we still must use Champion plugs as there seems to be no cross reference to any other brand.
Hope this helps.
macfam posted 02-23-2004 01:04 PM ET (US)     Profile for macfam  Send Email to macfam     
My next door neighbor has an Evinrude FICHT.
He replaces plugs every season,(very little use each season)(the indexing is a little tricky to "line-up" properly during installation)
At the dealer, they wanted $13.95 per plug.
He tried NAPA, PepBoys, etc, nobody carried the particular plug, except local dealers.
I led him to, and they charged $6.00 per plug and UPS shipping $5-6
So, if you order online, it's about half price.
Not a big deal.....but ya gotta hate spending $13.95 for each plug....6 run over $85.
Clark Roberts posted 02-23-2004 03:39 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
I changed the plugs in my 2000 Opti 135 at 200 hrs and replaced with NGK platinum at about $18 per plug as I recall. Very difficult to change as they are almost sideways and fuel injector electronics is in the way. These must be unpluged and layed aside and a 3/8 drive socket with universal joint and a 6" extension are needed. Also a plug wire puller (from auto store) may be necessary in order to remove plug boot and wire. After doing it once it will not be difficult the second time. I traded it in at about 500 hrs (only that one plug change but checked them each 100 hrs). My friend, Billy Clark has original plugs in his twin 1999 Opti 135s so plug life in the 135 Opti seems like a long one. Happy Skinned Knuckles... Clark... Spruce Creek Navy
Peter posted 02-23-2004 03:53 PM ET (US)     Profile for Peter  Send Email to Peter     
Changing plugs on an Evinrude FICHT is almost as easy as changing plugs on a OMC/Bombardier conventional outboard. Only difference is you must align or index the electrode so it does not block the spark in the direction of the injector. I'm told The plugs should last 100 hours if they are regapped at 50 hours. I change my plugs every season (50 to 75 hours) in any case so this would be normal maintenance for me. Sparkplugs cost about twice as much at the moment (~$5.00 vs. $2.50) because there is only one source.

kglinz posted 02-23-2004 06:04 PM ET (US)     Profile for kglinz  Send Email to kglinz     
My Mercury 225 Optimax came with Champions. One broke the porcelin. The dealer said I should have NGK, but Mercury would not replace them. Mercury did not notify owners they should be changed. As I read the plug, the broken porcelin was not caused by the quality of the plug, but by detonation and overheating.

On a 225 4 Stroke, removed plugs at 20 Hrs and at 110 Hrs. They were light tan, dry and the gap was good. They looked like a car plug.

dauntlass 18 posted 02-24-2004 07:57 AM ET (US)     Profile for dauntlass 18  Send Email to dauntlass 18     
I was sand- blasting, cleaning the plugs in my model year 2000 200-HP Optimax all summer long due to fouling.They were factory installed Champions. The second season of ownership at approximately 55-hours of use Mercury replaced plugs with NGK plugs as a warranty repair. When I contacted Mecury re the fouling problem it was left have dealer contact me. The dealer (not the selling dealer) handled the warranty details with Mercury. You need to work with a dealer who has trained people on DFI systems. At about 150 hours use I have pulled a few plugs to inspect; they are sill in great shape. When I replace plugs I will use NGK.
Moe posted 02-24-2004 09:19 AM ET (US)     Profile for Moe  Send Email to Moe     
Mercury 4-stroke 60HP Bigfoot EFI

Manuals says change at first 100 hours or first year, whichever comes first, and inspect thereafter at every 100 hours or year, whichever comes first, replacing as required. I pulled them at 35 hours to inspect and put high-temp antiseize compound on the threads. They looked good.

The plugs the factory supplied are Champion RA8HC, same as those used in late-model Harleys, K-series BMWs, and a huge range of Japanese ATVs and motorcycles. There are several cross-references to other brands, including NGK. I've been buying them for years cheapest (under $2) at independent bike shops, but you can get them at pretty much any motorcycle dealership. Many auto parts stores carry them as well.

They don't have to be indexed in the outboard. I do index them on the hot-rod Harley, but have proven to myself on the dyno, as others have found, that doesn't account for even 1 HP more. I HAVE found that using a plug that indexes correctly toward the center of chamber seems to make my two-stroke stuff (weedeater, chain saw, snowblower) start easier.

Let me provide a warning to those who would use platinum, gold, or iridium plugs for longer life, in aluminum heads. If the plug threads protrude into the chamber past the head threads, you still need to pull the plugs periodically and chase the carbon off the thread ends with the appropriate die. If the plug thread ends get heavily carboned up, and you try to force them out when you feel the resistance, the aluminum threads in the head will lose to the carbon.

jimh posted 02-24-2004 09:22 AM ET (US)     Profile for jimh  Send Email to jimh     
I appreciate all the comments and anecdotes regarding spark plug maintenance.

Does the owner's manual state a recommended normal maintenance interval for changing spark plugs?

I would like to get a feel for what the suggested interval is and what actual experience dictates is prudent with various brands of engines.

Any Yamaha low-emission owners out there? I don't believe I have heard any comments from owners of the Yamaha HPDI engine.

Much appreciated are comments about the difficulty in actually removing the plugs. This is often over-looked in considering the true expense of routine maintenance.

bsmotril posted 02-26-2004 09:51 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
On a pair of '97 Opti 135s, I replace the NGKs every 150 hrs. They still look pretty good other than some erosion of the sharp corners on the center electrodes. Dealer sells them for $20 apiece, NAPA around $18. I bought my last set via the web from an auto speed shop site on the west coast who had them on special for $11 ea. I know when it is time to replace them as the motor will get a very light occational miss in the 2800-3000 rpm range, which is right at the high end of the stratified charge running mode for an Opti. BillS
Fishcop posted 02-27-2004 11:34 AM ET (US)     Profile for Fishcop  Send Email to Fishcop     

Mercury Optimax manual states to inspect and clean the spark plugs every 100 hours or once a year. Replace spark plugs with NGK as needed. No indexing needed. Gap .040.

I replaced them on my 225 Optimax after 150 hours of use. $11 each from the NAPA Auto Parts. Same price from the dealer and online. Champion makes the same but is not recommended for heavy use by Mercury. $70 to keep a $15K motor running is not bad. Not cheap either!


jimh posted 02-27-2004 09:48 PM ET (US)     Profile for jimh  Send Email to jimh     
These first-hand accounts are great. Please keep them coming.

Does anyone own a Yamaha HPDI engine? Have you changed the spark plugs?

SuburbanBoy posted 02-29-2004 01:08 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
My Tohatsu gets a fresh set each year. I never clean plugs. If I pull them, I replace them. I always use Champion spark plug thread lubricant. It makes the plugs easier to remove each year. Additionally, I lubricate the ceramic with Silicone grease. It helps to reduce mis-fire and makes it easier to remove the plug wires. I use the factory recommended NGK's. They are plated to reduce corrosion. My Tohatsu is a carb motor, not injected.


jimh posted 02-29-2004 05:05 PM ET (US)     Profile for jimh  Send Email to jimh     
Is the Tohatsu outboard with carburetors a low-emission engine?
SuburbanBoy posted 02-29-2004 09:33 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
Nope, missed the low emisions title. (But it is a two stroke) Also missed a typo or two. Sorry


jimh posted 02-29-2004 11:57 PM ET (US)     Profile for jimh  Send Email to jimh     
Standard 2-stroke engine spark plug problems are rather well known, but it is the low-emission engines about which I am interested. Either 4-stroke or 2-stroke, I am looking for information about the spark plug maintenance on these engines.
dauntlass 18 posted 03-01-2004 06:18 PM ET (US)     Profile for dauntlass 18  Send Email to dauntlass 18     
If this is of any help to Optimax owners I understand you can use NGK Iridium plugs in your Optimax engines.The plug # is ZFR5FIX-11.I have not ck the dealer price but Club Plug on the web is selling them for 7.23 each vs the Plantium PZFR5F-11 at 11.31 each.I will ck Mercury first and if correct I am going to try the Iridium plug.The way my Plantium plugs look I should get another season out of them.
Rob Pirie posted 01-11-2007 08:55 PM ET (US)     Profile for Rob Pirie  Send Email to Rob Pirie     
A good trick for changing the plugs on your optimax without buying special tools is use is to place the top part of the spark plug inside a 6 inch piece of garden hose to guide the plug into the thread , this also ensures you will never cross thread it as you are only using finger pressure to start the plug and once it's wound in just tighten with your socket.


Mambo Minnow posted 01-12-2007 05:29 PM ET (US)     Profile for Mambo Minnow    
1999 200 Optimax...replaced the Champion plugs at 140 hours. It was not in the original manual...there was a later Service Bulletin advisory Mercury recommended switching to the NGK plugs at $15 each x 6 - $90.

I have used the NGKs for 50 hours. I have noticed I lost about 200-300 rpms over course of the season. I have not removed the plugs to inspect yet.

One warning my service tech friend told is very easy to strip the threads on the Optimax V6 powerhead. I would recommend against constantly removing the plugs for inspection unless you have a valid suspicion and/or all the best tools.

fourdfish posted 01-12-2007 06:53 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
As I have said on another thread I have 200hrs on my 200hp ETEC. Have not changed the plugs yet. I troll with it alternatively with my kicker. So most of those hrs are at cruise. I bought an extra set at for $7 with
shipping. Have not needed to change them yet but my dealer
who is friend of mine showed me how to index them.
NAPA said they would order them for $7.50 each.
Since this my 3rd year with the engine I will let everyone
know at end of year how the plugs look when I change them.
BRP calls for them to be changed at 3 yrs or 300hrs.
seahorse posted 01-12-2007 07:37 PM ET (US)     Profile for seahorse  Send Email to seahorse     
When the Yamaha HPDI was first introduced in 2000 it used a standard J-gap plug and advertised that a regular, not a high dollar plug, was used. Shortly after introduction there were a lot of plug fouling complaints and Yamaha redesigned the ignition system, coils, and ECU, and came out with a special dual-ground electrode fairly-expensive sparkplug. They only converted the motors whose owners complained and only when they were under factory warranty. It was a mid-year change so you have to go by serial number or whether the coils have black or gray colored connectors. One of the common plugs is NGK BKR7EK-U1 and is about $9.50 apiece.

The 250-300 HPDI motors get about 60-80 hours on a set of plugs. Much longer than that the motor runs smoothly but at a lower rpm. Usually a boater loses about 300 rpm. Install new plugs and the motor runs super again.

OptiMax hasn't used Champion plugs for a while. They were less expensive than the original $22 NGK ones, but did not last as long, hence the light duty recommendation. The newest Iridium plug is about $14.

sosmerc posted 01-12-2007 07:46 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
I agree with Mambo on this one. If your Optimax is running well, leave the spark plugs is too easy to mess things up due to the degree of difficulty getting at the plugs. (man, I do love the 3 cylinder Optimax engines...easy to get at everything!)
Good clean fuel, DFI oil, constant fuel treatment, correct propping....plugs should last a long time.
Binkie posted 01-12-2007 08:29 PM ET (US)     Profile for Binkie  Send Email to Binkie     
Wow, high dollar spark plugs,another good reason to stay with lower tec. outboards. Just changed the plugs on my `87 Suzuki DT150 super Six. $1.85 each, good thing, there are 12 of them.


Sal DiMercurio posted 01-12-2007 08:37 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Napa auto supply dosen't carry the plugs for my FICHT engine, they order them for me & come in, in 1 day.
Just picked up 6 & they went up from $4.52 each to $5.20 each, still better than the $12.00 $14.00 at the dealer.
When you go to Napa to order them, they don't know what your tawlking about if you say you need Qc12pep [ or whatever ] they need the Napa number which for my engine [ 200 FICHT ] & most e-tech engines [ same plug ] it's 956M.
A tip when indexing is to mark the plug with a marking pen right down the side where the electrod is open & also paint the plug socket with a line & put the plug in the socket so the opening on the electrod matches the line on the socket, that way you know exactly which way the plug is facing.
Any direction is fine except directly away from the injector.
Do not over tighten or use washers.
If 1 plug wont line up on this side, switch it over to the other side, it normally matches fine.
j_h_nimrod posted 01-13-2007 05:27 AM ET (US)     Profile for j_h_nimrod  Send Email to j_h_nimrod     
We have ~400 hrs on our 90hp Etec (QC12PEP) and have changed the plugs 3 times (one set at the end of the 400 hrs). After ~150 hrs you definitely can tell a difference with new plugs. We bought a service pack of 25 plugs and I have found ~1/2 will only index to one cylinder.

On another note we also have a 90 Ficht (QC12PEPB) that goes through a set of plugs about every 100 hrs. I have tried to regap and it only helps for a couple of hours. You can really tell when the Ficht needs new plugs; the motor becomes very rough and starts hard. I have usually had to buy 2 4-packs of plugs to get all the plugs to index within parameters (within +/-45 degrees of the injector).

Regarding indexing: do it! Uninformed people have changed the plugs on both engines without indexing and there is a very noticeable performance difference.

I had a NAPA counter jockey tell me that the difference between the QC12PEP and the QC12PEPB is just the platinum electrode. Both are double platinum; do not believe them!!! There is a slight difference in reach and the resistor (CDI vs. inductive) is different in each. Does it make a difference? I do not really know. The QC12PEP seemed to work fine in the Ficht but it is .05mm shorter then the QC12PEPB and that could make the difference in the Etec.

seahorse posted 01-13-2007 07:13 AM ET (US)     Profile for seahorse  Send Email to seahorse     

Your 90hp FICHT uses Champion XC12PEPb plugs, NOT the QC12PEP plugs.
fourdfish posted 01-13-2007 08:04 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
I have been led to believe the larger block engines are easier on plugs than smaller engines. I have also heard that trolling is hard on the plugs. So far I cannot say with experience on this. I'm sure Seahorse knows more about it than I do on this!
At any rate 400hrs on a set of plugs is fine with me.
bsmotril posted 01-14-2007 01:48 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
On a pair of early model Opti 135 V6, I was getting about 125 hrs to a set of plugs. The plugs were expensive Nippodenso platinum tipped at about $12 each. But, I found them online at a few stores that sell to Jap Car Tuners for considerably less than that. BillS
KJS posted 02-15-2007 11:28 PM ET (US)     Profile for KJS  Send Email to KJS     
Hope this helps. I own a Yamaha 300hp HPDI and it loves sparkplugs. I only get between 30 to 40 hours on a set of NGK double grounded plugs. The engine performs very well with fresh plugs. When they start to foul you will notice a small miss at idle and wide open throttle. The price at with shipping will run about $6.00 each. I have friends with the 225 hp models that have no problems at all. Change once a year and let her rip. I love this engine but I hope Yamaha can help. I will update if I get answers.
lakeman posted 02-19-2007 04:19 PM ET (US)     Profile for lakeman  Send Email to lakeman     
I just purchased the expensive plugs for my Opti at Advance Auto for $10 dollars a piece and the store clerk said they usually have them in stock. I did this at the store near me. I tried Advances web site but they were much more expensive. I cannot understand that.
By the way, Advance near me has some good prices on Collonite insulator wax and Starton as well.
Chuck Tribolet posted 02-20-2007 06:10 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Those platinum plugs should be lasting longer. My Nissan
Pathfinder has a 100,000 mile plug change interval. At
60 MPH that's 1667 hours. And this is in a fairly high-strung
engine that gets 1.17 HP per cubic inch.


itl posted 02-27-2007 09:22 AM ET (US)     Profile for itl  Send Email to itl     
You should try NGK Iridium plugs with Opti engines. Those plugs are very good but expensive too.

Use to own 115hp 3-pot Opti. I did run more than 300 hours with one iridium plug set. My plan was to test how long plugs really works, but the test was prematurely interrupted, because I change my boat/motor to another one before my plugs died.

How ever, no problems with the plugs what so ever. Plugs were in good shape after more than 300 hours. Would expect that plugs might last even 400 hours. Can really recommended NGK iridiums.

Plug type for 75-90-115hp Opti is: NGK IZFR5J.

Intermarine usa posted 03-05-2007 05:06 PM ET (US)     Profile for Intermarine usa  Send Email to Intermarine usa     
The owner's manual for my 2004 Yamaha 300HPDI's calls for NGK BKR6EKU spark plugs. However my Dealer and most on-line parts catalogs call for BKR7EKU plugs. What gives? Which plugs should I really be using?

Thanks in advance for your help!

Intermarine USA

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