Yamaha OX66 250hp Spark Plugs - The Hull Truth

First Light · 06-29-2003, 07:34 AM

Anyone have a handle on which spark plugs are best for a 2002 OX66 250hp Yamaha? Thanks.

Cracker · 06-29-2003, 08:28 AM

Any part store should be able to help you but DEFINITELY stick to NGK! Jap motors, Jap plugs!

t bone · 06-30-2003, 06:39 AM

I go to the nearest yamaha dealer in my area for my plugs etc.. they come pre gapped (i do check em all anyway) and cracker is right NGK!!

KevinM · 06-30-2003, 07:31 AM

Get the part number, and buy them from a Pep Boys or discount auto type store. You should be able to get them for about $1.69 a plug! Boat store or Yamaha dealer will get youi for almost $3a plug. Using the part number that is in your book should get you the pre-gapped plugs. For instance take the BR9HS10, the 10 designates the pre gap.
If they only have the plugs without the last digit (BR9HS) this designates you will have to gap them. Same plug.

First Light · 06-30-2003, 11:13 AM

Kevin (or anyone else): The manual says BR9HS(10) and there is also a small sticker on the inside of pan just below the lower spark plug on the post side of the engine that also says BR9HS. However, the engine was last serviced (and plugs changed) by Caribee in Islamorada, one of Yamaha's larger sales and service dealers and they installed BR8HS plugs.

Anyone know the difference in the "9" and "8" numeral in the NKG spark plugs? I'm assuming one runs hotter and one runs cooler. Caribee is a large volumn Yamaha sales and service dealer and I hear nothing but good things about their service - just wondering why they would have installed BR8HS plugs rather than the recommended BR9HS? And I'm sure the reason is NOT because they were out of BR9HS's.

KevinM · 07-01-2003, 07:40 AM

The lower the number on NGK signifies a hotter plug. Here is the key for NGK:
B = 14mm thread
R = resister
# = heat range 1 is hottest 11 is coldest
H = thread reach 12mm
S = firing end construction S = standard center electrode
# = the pre-set gap 8mm thru 20mm (10 = 10mm or
.040"), no number = installer needs to gap

Piddler · 07-01-2003, 09:05 AM

When all else fails, go to the source:

http://www.ngksparkplugs.com/products/index.asp

Piddler

First Light · 07-01-2003, 12:54 PM

Got so curious why one of their larger dealers would install a non-recommended spark plug (NKG BR8HS) I finally found someone at Yamahama today who knew why, and HE said (quote): "in most applications the BR9HS is the plug we recommend in the OX66 250hp. However, if you use your engine to do a lot of trolling, the BR9HS will load up at excessive low RPM use, and in these instances, we recommend the BR8HS."

Piddler · 07-01-2003, 01:28 PM

Glad you got a response from Yamaha. For the reasons you quoted from your Yamaha source, the heat range of the normal OEM plugs is sometimes adjusted to conform to the current use the engine is put to.

You must have supplied Yamaha with info we were not privy to, i.e., that you do a lot of trolling.

Piddler