[DavidRT2T]

I have a 1994 Evinrude 175 Intruder. It is currently running NGK BR9HS-10 plugs and the NGK Book calls for BPZ8HS-10 which I understand to be an inductive Resistor plug made for CDI ignitions. My first question is is this the correct plug (the BPZ8HS-10) and why would the other plug ever be used if it wasnt correct? Question 2 is the NGK book and website say the Gap should be .030 but the plug comes pre-gapped at .040......which is correct?

[Paul Moir]

According to boatsetup, the correct plug is a Champion QL78YC, gapped at .030. Johnson/Evinrude engines and NGK sparkplugs do not get along well for some reason.PS - the BPZ plug has a choke (inductor) in it rather than a carbon resistor, like the BR plug. A choke is appropriate for a CDI ignition since it suppresses ringing. I expect the reason you had BR plugs in it is that they're cheaper than BPZ. I don't know why they felt they needed a colder plug (the 9 instead of 8).Good luck!

[DavidRT2T]

Paul, Thanks for the info. What you tell me jives with what NGK told me. The boat has been running Great on the NGK so I will stick with them even though they are VERY expensive. I just noticed the manual says Champion QL77JC4.....why so many different plug options?

[bradley1393]

The ql plugs are the correct ones. Not often will you get me to put anything but ngk in an outboard.... but the omc are very finicky about their plugs. If you have any idle or stumbling problems you might want to switch to the champions. By the way the -10 on your ngk plug is actually a preset gap of 1.0 mm -8 = .8 mm etc.

[Paul Moir]

I think there was an updated recommendation on that engine. Anyway, they're not that much difference between a QL78YC and a QL77JC4: Q is for the inductive resistor.L is the length of the threaded part of the plug (.472")77 or 78 is the heat range. Too cold and the plug will foul, too hot and it's a site for pre-ignition (bad). For champion plugs, heat range goes up with number. NGK goes down. Heat range is specific to an engine. There's very little difference between 77 and 78.Y has a protruding ground, J has a cutback electrode.C indicates a round ground electrode with a sawed gap.4 is the production gap (0.044").NGK uses a different nomenclature, but it works a lot the same way.Like Bradley, I have no warm spot in my heart for Champion plugs, but they do work better in OMC outboards. Oh, and I think you'll find they're a lot cheaper than the proper NGK plugs.Hope this helps!

[DJ]

David,LOSE the NGK's. As said, OMC's don't like them. I'm no fan of Champ's but the the OMC engines run better on them.

[DavidRT2T]

WOW, I guess I should think about the champion plugs. I went to sparkplugs.com and used the champion plug finder and it says to use the champion marine 5939 plug????? Its description sounds similar to the NGK plug and it is also VERY PRICEY. I am so confused. Is the gap .030 correct no matter what plug and what factory plug preset gap is???? Thanks again.

[Paul Moir]

The 5939 plug is very nice. I'm sure the stainless steel jacket will still look all shiney a year from now when you throw the sparkplug in the garbage while your doing your routine maintaince. Get the equivalant mild steel jacketed QL78YC and pocket the difference. I guarantee your garbage can won't know the difference. Gap it to 0.030 no matter what the factory builds the spark plug at. That's just a conveniance for people who don't know how to do it in NGK's case. In Champion's it seems to just be a coincedance they like to report. The size of the gap is mostly governed by the ignition system and RPM operating range of an engine, so follow the engine's manufacturers recomendation.Hope this helps.