These are engines. How you "drive" the engine does determine the spark plug life. Unless you have platinum plugs, you do have to replace them, especially if you do a lot of idling, stop and go, etc. Think of a car in traffic, versus a car running on the highway.
I pretty much follow the 200 hour tune-up guide as I tend to do about 50% cruising and 50% stop and go (tubing, skiing, fishing, trolling, etc).
They get fouled, do breakdown, etc. There are marine grade plugs - stainless, etc. I'm not sure about performance based.
I replaced the plugs in an 1988 Merc. 5.0L engine. I don't know how old they were when I bought the boat, but they looked like a normal wear and tear on a 12,000 mile plug from an engine.
So... for the cost, the performance and economy gain are worth it. Don't forget the rest of the tune-up stuff, including filters! Is platinum worth it??? That's your call based on amount of usage and how you use it.
IMHO...
spark plugs
Re: spark plugs
). Seriously though, I think there is a reason, but I can't remember right now. If that's the case, there probably isn't much of a "performance" choice out there. I'll do some more research...
