Spark plugs Yamaha 150 carbed

Blue_Runner

Blue_Runner

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Staff member
Here is the story. With saltwater use I like to change the plugs in my 2004 Yamaha 150 every year. Well, I went to buy plugs this year and got the number off one plug so I could buy the new ones. NGK BR8HS-10. So I bought 6 BR8HS-10 plugs. Got home, went to replace them and realized I had 1 BR8HS-10 and FIVE BR7HS-10 in the motor all season. So, my questions....

1) Any repercussions from running like this all this time?
2) Should I go back with BR7HS-10, or BR8HS-10. I think one is hotter, but not smart enough to know which one.

I looked at them and with my untrained eye they all appear to look good and about the same across all 6.

Apparently when I bought them last they accidentally gave me one BR8HS-10 and I did not notice. I am thinking BR7HS-10 is what I want but need expert advice!!!!

p.s. note to self - always double check new plugs are the same before you put them in!
 
8s are one heat range colder than 7s, you'll be fine. If you are a doing a lot of trolling, the 7's may serve you better
 
No more than 5 seconds after reading that last post I found the sticker in the lower pan. BR7HS-10! Thanks guys!!
 
These guys are a lot smarter than me about these things but what I would do is go with what is recommended for that engine Why you ask? Because when they build that engine it was designed to run on those plugs
 
Some manufacturers will have 2 plug reccomendations for 1 engine depending on useage. Match the plugs to the engine and it's useage. If you idle alot you can normally run 1 heat range hotter, but you want to be carefull running a hotter plug at high rpm's as it can overheat and melt the plug and lead to detonation from the plug overheating. Omc used to reccomend surface gaps for engines run hard, and a long reach electrode for engines that idled alot. If you ran under varying conditions, you used a plug where the electrode was right on the surface to be in between. If in doubt, save an old set of plugs and carry a wrench to change them, and run the colder plugs. I would rather foul a plug than I would melt a plug and lose an engine. And if it's a dfi, make sure and index the plugs if it's reccomended. It's always best to have your firing gap pointing towards thecenter or towards the exhaust to minimize plug fouling.
 
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