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Author Topic:   Mercury Spark Gap and Recommended Spark Plugs
jeff4921 posted 11-16-2005 05:45 PM ET (US)   Profile for jeff4921   Send Email to jeff4921  
I recently purchased a 2001, 200hp, 2-stroke, 6-cyclinder Mercury Outboard for my boat. What is ehe best type of spark plug and what gap it should be set at for this motor. Model #1-200425yd. Was wondering if anyone could tell me this.
LHG posted 11-16-2005 06:43 PM ET (US)     Profile for LHG    
Mercury V-6's don't use gapped plugs. They are a center electrode type, NGK BU8H, so this one worry you won't have..
LHG posted 11-16-2005 06:44 PM ET (US)     Profile for LHG    
Mercury V-6's don't use gapped plugs. They are a center electrode type, NGK BU8H, so this one worry you won't have..
rtk posted 11-16-2005 09:05 PM ET (US)     Profile for rtk  Send Email to rtk     
My 2003 Mercury 250 EFI uses Champion QL77CC, gapped at .035 inches/ .90 mm.

My manual lists a 200/225/250 horsepower, all the same plugs.

The small block V6 may use the spark plug LHG lists. The owners manual for the engine lists the recommended spark plug for your motor.

My manual states that using the incorrect spark plug may cause engine damage, so be careful.


Chuck Tribolet posted 11-16-2005 10:10 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I think the most important thing is "what plugs did the
factory use on the dyno?" It's highly likely that's what
the other engine parameters are optimized to. NGKs are good
plugs. My Nissans (all five) have run them. That's the
factory plug. But my Evinrude specs a Champion, and that's
what I run there.


LHG posted 11-16-2005 09:28 PM ET (US)     Profile for LHG    
Thanks for correcting that bad information rtk. Since my 1985 in-line 6's also use center electrode plugs, I assume the 3.0 liter would too. Also, NGK plugs are spec'd for almost all Mercury engines now, so here too I am surprised to see Champion making a re-appearance. For many years, all I heard from Merc mechanics was they were junk and not to be used. Oh well. Can't believe what you read on the Internet!
jimh posted 11-16-2005 10:22 PM ET (US)     Profile for jimh  Send Email to jimh     
I cannot tell you the recommended spark plug or the proper spark plug gap for your late-model Mercury outboard motor. In general the website does not try to collect and organize that information.

The recommended spark plug for your motor is generally given in the owner's manual. The recommended spark plug gap is also given there.

I strongly recommend that you read the owner's manual. It will be filled with important information to help you operate and maintain your motor.

If you do not have a copy of the owner's manual, I recommend you purchase a copy from your local authorized Mercury dealer. They often have these in stock or can order them for quick delivery. Or they can advise you where you can obtain one.

Having an owner's manual is a valuable tool in learning more about your engine, how to operate it, and how to maintain it.

[This thread was separated from another, older discussion on a different topic.]

rtk posted 11-17-2005 12:17 AM ET (US)     Profile for rtk  Send Email to rtk     
I have heard the same thing quite often about the use of Champion plugs, and alot of mechanics were recommending an NGK equivilent Larry- so you are not imagining things.

I like to inspect my spark plugs a few times during the season. I noticed the plugs always had black deposits on them, and some oil, basically lightly fouled. A couple of months ago I did install the NGK equivilent plug. After running the boat for approximately two months, I checked the plugs. The NGK plug was a nice light brown color, and no evidence of any fouling. I also experienced a top speed increase of close to two miles per hour, and a bit better fuel economy. At idle, it did not seem to run as smooth as the Champion plugs though.

I did change a couple of other things too:

1) No Mercury Quickclean to the fuel as I religiously did at fill up

2) Switched to a synthetic blend two stroke outboard oil

3) Switched my source of gasoline. (I used to fill up at a marina that offered the Boat US discount. I had an expired card with me- they would not honor it, even though my membership was paid well in advance) They will not get a piece of my 600 gallons I usually purchase in a season from now on :)

I changed the plugs back to the Chanmpions recommended in my engine manual about a month ago. (new set of plugs) I wanted to see if they would show the same fouling, running the same fuel and oil as the NGK plugs for a fair comparison. I have not checked the Champions yet, but I will this weekend.

If anyone does have any input on the Champion vs NGK plugs for this engine I would be very interested in the information.


LHG posted 11-17-2005 01:19 AM ET (US)     Profile for LHG    
Regarding the 2.5 liter V-6 Jeff is asking about, I stick by my first post. Those are the correct plugs, as recommended in the Owners manual.
jeff4921 posted 11-18-2005 04:52 PM ET (US)     Profile for jeff4921  Send Email to jeff4921     
Thanks for the information gentleman. I removed 1 of the old spark plugs from the motor and it is a Champion QL78YC. Maybe because its not a fuel injected motor its a different plug then rtk's. Or maybe its not the right spark plug at all. If it is the right spark plug is there an eqivalent NKG plug?
gss036 posted 11-18-2005 05:33 PM ET (US)     Profile for gss036  Send Email to gss036     
NGK Standard BPZ8HS-10 part# 3133 .040 gap for the 2000&2001 200hp Merc EFI.
nydealer posted 11-20-2005 09:26 AM ET (US)     Profile for nydealer  Send Email to nydealer     
go to your local mercury dealer with your serial number and they can tell you the exact spec. Post or email the serial number to me and I would be happy to look it up for you.
jeff4921 posted 11-20-2005 12:48 PM ET (US)     Profile for jeff4921  Send Email to jeff4921     
Thanks nydealer. Serial # is 0T391569. I'm not sure if the first digit is a zero or the letter "O".
jeff4921 posted 11-22-2005 05:01 PM ET (US)     Profile for jeff4921  Send Email to jeff4921     
I called the Mercury/Force manufacturer directly (1-920-929-5040)and got the information I needed. NGK-BPZ8HS-10 spark plug-Gap .040.
gss036 posted 11-22-2005 08:02 PM ET (US)     Profile for gss036  Send Email to gss036     
That is the same number I posted lst week. It came straight from NGK.
dauntlass 18 posted 11-24-2005 04:19 PM ET (US)     Profile for dauntlass 18  Send Email to dauntlass 18     
My model year 2000 ,200 hp Optimax came from Mercury with Champion plugs in it.They were a constant fouling problem.Mercury replaced the plugs with NGK plugs no fouling since replacement with NGK plugs. I guess I have about 150 hours time on the plugs.My manual says Champion QC12GMC for standard use and NGK PZRF5F-1 for severe use.I have been told Mercury now reccomends a NGK Iridum plug for Optimax motors.If it is of interest I was useing Optimax oil with both plugs.

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