Spark plug life ?

[dls]

2020 250 Pro XS ser. #2B743128
My first set of plugs lasted 148 hrs but I was only using Quickare. After replacing the plugs and reading Don's suggestion on additives I now run Quickare and Quickleen with every tank. How long should I expect the plugs to last now. I noticed my last time out that right after planning off and before trimming up the motor had a brief suttule surge for about 2 seconds. It started doing the same thing but with a more pronounced surge before I changed them at 148 hrs which took care of the surge. My new plugs have 41 hrs on them now. This was my first time out in 5 weeks. Could that be the reason or do I need another set of plugs. Idle is smooth and WOT rpm's are 6000 with a full tank (53 gal).

[EuropeanAM]

Life of plugs will vary based on additives, fuel quality, octane used, and how it's run (idle and WOT are the worst run-times for spark plugs on this engine).

An engine with 41 hours on a set of plugs that's been below 1500 RPM's for 22 of those hours could potentially need plugs currently (especially if they're more than a year old).

[dls]

Life of plugs will vary based on additives, fuel quality, octane used, and how it's run (idle and WOT are the worst run-times for spark plugs on this engine).

An engine with 41 hours on a set of plugs that's been below 1500 RPM's for 22 of those hours could potentially need plugs currently (especially if they're more than a year old).

2020 250 Pro XS ser. #2B743128 I only run 87 octane in top tier fuels such as Exxon. I do idle some of course but majority of hrs. is at 5000 to wot. What rpm range is best for this engine ?

[Pulsare2020]

Life of plugs will vary based on additives, fuel quality, octane used, and how it's run (idle and WOT are the worst run-times for spark plugs on this engine).

An engine with 41 hours on a set of plugs that's been below 1500 RPM's for 22 of those hours could potentially need plugs currently (especially if they're more than a year old).

To add to Don's post, I have changed plugs on my 300R twice, and always below 100 hours. The engine told me it was time to change plugs and the plug change restored the performance. Based on years of changing plugs on many other vehicles, the plugs always "looked fine". All looked identical and all none looked like they were misfiring or rich (lean if anything). I even checked the resistance of all the used plugs and they were within NGK's range. So I learned that I can't go by "looks". So I change them when the engine starts to tell me it might be time to change them.

[Welaka]

Out of curiosity. Why such short life on 4 stroke marine plugs? New cars are 100k lifespan. Depending on driving habits. Possibly 2000 hours on highway vehicles. Is it temperature related?

[Pulsare2020]

Out of curiosity. Why such short life on 4 stroke marine plugs? New cars are 100k lifespan. Depending on driving habits. Possibly 2000 hours on highway vehicles. Is it temperature related?

That's a good question and I have wondered myself. Most auto plugs today are iridium or similar upscale plugs, but even if we used the correct heat range copper NGK plug in our vehicles they would last significantly longer than a 4 stroke outboard? Perhaps the heat range is chosen cold enough to ensure no detonation at WOT for 30 minutes or more (would never happen in a street car) so they would be more prone to foul at prolonged idle speeds, but I have never seen a plug that looked fouled or carboned over, they looked good but developed a miss. I'm sure Don has some better answers for all of us.

[Capt James]

To add to Don's post, I have changed plugs on my 300R twice, and always below 100 hours. The engine told me it was time to change plugs and the plug change restored the performance. Based on years of changing plugs on many other vehicles, the plugs always "looked fine". All looked identical and all none looked like they were misfiring or rich (lean if anything). I even checked the resistance of all the used plugs and they were within NGK's range. So I learned that I can't go by "looks". So I change them when the engine starts to tell me it might be time to change them.

This is exactly what I had to do.....change the plugs at just over 100 hours. They all looked lean and fine.

[fishnfireman]

Changed my 250R plugs at 300 hrs.
I did not notice any performance issues before changing and didn't notice any gains after changing.
Have over 250 hours on this set and will change again at 300.

[EuropeanAM]

Out of curiosity. Why such short life on 4 stroke marine plugs? New cars are 100k lifespan. Depending on driving habits. Possibly 2000 hours on highway vehicles. Is it temperature related?

Very harsh environment as compared to your automobile or truck. And a very different duty cycle as well (think about the extended RPM's your engine turns, quite different from most automotive applications, other than perhaps racing).

[berudd]

Very harsh environment as compared to your automobile or truck. And a very different duty cycle as well (think about the extended RPM's your engine turns, quite different from most automotive applications, other than perhaps racing).

Do you know what AFR these engines typically run at? If they tend to be much richer, that could lead to shorter plug life.

[Mcjenson]

Very harsh environment as compared to your automobile or truck. And a very different duty cycle as well (think about the extended RPM's your engine turns, quite different from most automotive applications, other than perhaps racing).

Exactly. Imagine taking your car out and either running redline rpms in first gear or idling at stop lights with little in between

[bloodman]

Exactly. Imagine taking your car out and either running redline rpms in first gear or idling at stop lights with little in between

Done that to plenty of cars with no plug issues.
Gotta be a significant difference in outboard ignition

[fishnfireman]

Exactly. Imagine taking your car out and either running redline rpms in first gear or idling at stop lights with little in between

maybe that's one reason my plugs were still ok at 300 hrs.
I can get on plane with 1/4 throttle and do most of my running in the 4000 to 5500 rpm range.

[Woody b]

Comparing boat engines to automobile engines is like comparing apples to grapes.

There is and will continue to be advancements in boat engine technology that mirror automotive technology but I don't think we'll see the equivalent of 100,000 mile spark plug changes in boats anytime soon.
Many of the auto and light truck applications that either have higher cylinder pressures, or generally harder working engines require spark plug replacement every 30,000 miles.

[EuropeanAM]

maybe that's one reason my plugs were still ok at 300 hrs.
I can get on plane with 1/4 throttle and do most of my running in the 4000 to 5500 rpm range.

^^^^ And that's where Advanced Range Optimization will be active, which trims the fuel delivery to achieve absolute best economy.

As for the question of Air/Fuel Ratio: Stoichiometric Ratio when fully warmed up at sea level (that's the APPROXIMATE base table) plus or minus up to 20% for operational and atmospheric variables.

Cold engine or above 1200ft elevation is going to be a whole different ball-game (which is why there are so many map tables for the PCM to pull from).

[Mcjenson]

Done that to plenty of cars with no plug issues.
Gotta be a significant difference in outboard ignition

You run car engines for miles at redline rpm’s?

[EuropeanAM]

You run car engines for miles at redline rpm’s?

And still get 100K miles out of the engine the spark plugs are in?

[bloodman]

You run car engines for miles at redline rpm’s?

No but pretty severe and idled for many many hours.
I dont run my OB that way though

[Pulsare2020]

A question for Don. Back in the 70s & 80s I owned a Merc 50, 85, and 140 TOP (all carburated 2 strokes of course). All used those Champion surface gap plugs if I recall correctly. I never remember ever replacing them because they were fouled, just inspecting them and wiping them off with brake cleaner. Why did they last so long?

[fly by night]

I put a new spark plug in Honda 4 stroke 2.3 HP motor this year when it wouldn't start. The old one was 12 years old. I purchased it in 2012 but it has had very little use.