In my service manual, it shows that for my motor, 91 150 Fast Strike, it is supposed to have QL77JC4 plugs. On the spark plug chart in the forum, it shows QL78YC. The motor now has the 78's in it. I am changing the plugs but wondering which ones are the correct ones. Any help would be great guys.
J150GLEIS
Ranger 198p
Yamaha 150 SHO
Atlas jackplate
Ultrex I-pilot
2 Solix 12's
Hummingbird 360
Rigid deck and trolling motor lights.
Use the QL78YC Champions and nothing else.
I think the 77's are for a crossflow.
Modified by Lockjaw at 11:08 AM 2/15/2009
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96 Javelin 379SE 96 Johnson 150 (J150ELEDB)
Mods: FS carbs, Ficht reed cages, boyesen reeds and
Baker Hot Heads.
Champion also makes a Stainless Steel Marine plug........3979, for this engine. I just installed a set last week. i got them thru my local NAPA store. No worries about rust and say they offer smoother idle and fuel economy.
David Howell
1997 Javelin 389TE
Johnson 150 Fast Strike
Arlington, Texas
Back in about 1995, OMC changed the spark plug recommendations to take advantage of newer styles on the market.
Your 18 year old owners manual is out of date. The QL77's work OK but the extended nose on the QL78YC's run a lot better, especially at low speeds.
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A Technical troubleshooter possessing more tools than talent !
Ranger 198p
Yamaha 150 SHO
Atlas jackplate
Ultrex I-pilot
2 Solix 12's
Hummingbird 360
Rigid deck and trolling motor lights.
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