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10 Best Marine Spark Plugs for Your Boat 2024 – Accessories for Boat Engine

Marine Spark Plugs Boat

So, you want to go out for a fun fishing ride in the ocean with your family. You have your very own boat sitting in the harbor for days. Then you find out that your engine is struggling to start.

We’ve all faced this with our cars. A failed spark plug forcing us to use the subway, we’ve all been there. And the same can happen with your boat too.

So for finding a replacement, we’ve gathered the best marine spark plugs here. This was hard since we had to get our hands dirty and shuffle through twenty different spark plugs. But we did it for you!

We’ve even added a cool little buying guide towards the end only for you. So check that one out too.

Top Picks Review

1. NGK 3623 Spark Plug

NGK 3623 Spark Plug

Product Overview

The first on the list is this pack of 10 from NGK. We had a lot of reasons to put this one on top. And we’re going to talk to you about all of them.

We always give credit where it’s due. And NGK pulled off a ten-pack with the lowest price on the list. There, we said it, and you can’t get a more value-for-money option than this one.

But we still think that it’s a shame that you can’t just get one spark plug. I mean, there will be times when only one of your spark plugs fails. And, you won’t need 10, right? But I still think this is a decent deal, and this alone is enough to seal its place on top.

Let’s move on to the practicality of things now. I mean, they claim a lot of things, but you don’t need to be going to see them in real life.

They say that these spark plugs have been specifically designed to operate in a wider heat range. But it’s a bold claim and quite vague too. Especially because we’ve seen other companies make the same claim with zero commitments.

We took a spark plug out of our boat to test these out. It did what a spark plug is supposed to do. We don’t mean to get a bit technical here. But the plugs give out the sparks that eventually go on to light the fuel-air mixture.

This is what gets your boat engine or any combustion engine going, for that matter. It’s actually pretty fascinating seeing what a small device like this can do.

They boast a lot about their “triple gasket sealing” process. We’re not sure what they mean by this. But they claim that it stops the slightest possibility of leaking combustion gas.

Well, I’m no engineer who designs these things for fun, but in our short time with this one, we didn’t observe any gas leakage at all. But that’s to be expected.

  • Prevents leakage of combustion gas
  • Can handle higher temperatures than usual
  • Improved heat transferring between surfaces
  • Passively works against carbon buildup
  • Decent durability
  • One out of ten has a chance of being defective
  • It might not last over a couple of years


2. Quicksilver AC Delco MR43T Spark Plug

Quicksilver AC Delco MR43T Spark Plug

Product Overview

Coming in second place is this spark plug from Quicksilver. This one almost made it to the top of the list. But a couple of things held it back. So, let’s talk about it.

Just like the first one, this has a copper core. This is the most common material that companies use for the cores. And, that’s because it’s reliable. I’m not saying other materials are bad, but we’ll get to it in a bit.

The copper core inside this spark plug is said to promote better heat transfer qualities. Well, it’s true, that’s why companies have been using this for so long.

There’s this fact going around that copper spark plugs are more durable. We didn’t get much time to play around with this one. But this spark plug didn’t seem to fail us.

This one is the second cheapest on the list. And, you can buy just one. But things will start to add up eventually if you need multiple spark plugs, in case all of your spark plugs fail.

Quicksilver has this “rubber suppressor seal.” We thought this was a gimmick. I mean, the job of a spark plug is to ignite. And if you see misfires in the engine, it’s possible that the plug failed. So we’re not too sure whether their technology for preventing misfires works in reality or not.

The central electrode has a sheathing of a type of nickel-chrome alloy. While they claim that this will aid in the fight against corrosion, we’re not certain.

If spark plugs do come in contact with moisture, they might still get corroded. So, you never know.

They focus on protection a lot. We appreciate the fact that the plug is said to be compatible with all the brands.

  • Prevents corrosion
  • Passively tries to prevent misfires
  • Better heat transferring capability
  • Affordable option
  • Fits perfectly
  • Might not be good in the long run
  • Might burn out soon


3. NGK 5422 Spark Plug

NGK 5422 Spark Plug

Product Overview

Next up, we have another one from NGK. This one might not be as good as the first one. Well, that’s kind of obvious since it’s not in the top two. But it did just enough to secure a podium finish.

The first thing we liked about it is that they give you options. You can either choose a pack of 4 plugs or order just one. There are situations where you might need all four.

And I’m pretty sure there will be the more common scenario of you needing just one more spark plug. That’s because it’s just that one failed spark plug that’s keeping you from venturing onto the seas.

They claim that it’s better than any ordinary plug. It could be, you never know. We didn’t come to see any special features on this one, though.

The summer heat should’ve added a couple of more degrees to the engine. So it went pretty hot, I must say. So it’s nice to see that this one held up decently.

We’ve come across many subpar plugs that had pre-ignition issues. So we had to discard them. But this one didn’t show any carbon buildup during our short time of use.

It’s safe to say that after our month-long review, this plug survived. But we’d like to add that this does not represent what would happen if you were to use this for a whole year or two.

What’s with companies promoting their “high alumina ceramics”? We’ve seen these terms being used all over the place.

Although the heat transferring system seemed decent, we don’t think this technology had anything to do with this. The electrical insulation was decent too. We didn’t have any complaints in this regard.

  • Comes with decent versatility
  • Reduces chances of corrosion
  • Performs decently while under high heat
  • Gives you a couple of choices
  • It offers a good fit
  • Might start acting up in a month or two
  • Not suitable for long-term use


4. ACDelco MR43T Spark Plug

ACDelco MR43T Spark Plug

Product Overview

Coming in at 4th place is this one from ACDelco. It’s very similar to the previous ones. But we’ll talk about how this one gotta be so much lower down the list.

You can only order the one-piece version. So, we thought that it was kind of on the expensive side for just one plug.

They claim that the tip is sheathed with a nickel alloy. So this should give the minimum amount of protection. There’s this “ribbed suppressor seal,” which they use for better durability.

Since we’re no expert engineers, we’re not sure if it’s doing its job. But we didn’t see any issues worth mentioning.

They do warn you about using the recommended spark plug for your engine. Not a lot of manufacturers do that nowadays, so we’re going to give them credit for this.

We think all of us should get new plugs installed after using the previous ones for years. Even if the plugs didn’t fail, you could probably tell that it’s about to go sooner or later. So a change in spark plugs can only future-proof your engine.

Another tip that we’d like to give out is that you should probably try to change all the plugs together. Replacing all of them at the same time should be a good choice.

And the good thing about these types of plugs is that you know you’ll need them sooner or later. Even if your boat is fine, you can install one of these onto your truck since these little guys are so versatile

  • Decent versatility for combustion engines
  • Runs like clockwork on most boat engines
  • Can withstand a higher temperature
  • Easy to plug in
  • Might prevent rusting
  • A bit expensive for just one plug
  • Might not be compatible with all boat engines


5. ACDelco 41-994 Professional Iridium Spark Plug

ACDelco 41-994 Professional Iridium Spark Plug

Product Overview

Here’s another one from ACDelco. This one’s a bit different from the other plugs on the list. And, this will only cater to a limited number of people, we figured. So let’s talk about it.

The first thing that we’d like to point out is that you get choices. You can either order just one or pick a pack of 4. This is good because you might not need more than one at a time. And, sometimes, you might need all four plugs.

But it’s fair to say that some of you would be aiming for the previous ones mentioned on the list rather than this one. And, the main reason for this is the price.

This is, by far, the most expensive set of spark plugs on this list. You can get ten pieces of the first one for almost the same price as one plug of this one. So, you can probably guess where we’re going with this.

We don’t recommend this over the other four that we just reviewed. But there might still be a reason why you might want this.

The key feature here is the iridium core. None of the other plugs on the list have an iridium core. It’s said to offer improved engine stability when compared to copper.

We have to admit that cold starts are easier when you’re using iridium spark plugs. These plugs are harder and will probably last longer than any copper core spark plug.

The only drawback that we see with iridium plugs is that they are overpriced if you compare them with the normal copper ones.

This particular plug has features like suppressor seals which might help out when trying to block out radio frequencies. We couldn’t really put this to the test, but we decided to take their word for it.

It’s not the best spark plug in the world. But if you fancy iridium cores, this is the only choice you have.

  • Made of a durable core
  • Has a long lifespan
  • Protects from combustion gas leakages
  • Efficient and hard electrode design
  • Easy to plug in
  • On the expensive side
  • May not be compatible with all engines


6. Champion 828M Pack of 4 Copper Marine Spark Plug

Champion 828M Pack of 4 Copper Marine Spark Plug

Product Overview

It’s time to end this list with this one from Champion. The packaging looked great to us. But that might be the only good thing about this one. Let’s talk about the details.

It’s a pack of four. So it’s a shame that you can’t get just one of these spark plugs. You have to order the whole pack. It’s the second most expensive set on the list. Even though it doesn’t have an iridium core or a platinum core, it’s expensive. And, we honestly don’t know why.

They boast about all the good things like better resistance to corrosion or improved electric conductivity. The summer heat allowed our boat engine to go pretty hot this time. But the plug worked fine as it should. We did not come across any issues which seemed to be problematic.

It’s safe to say that you might not get the exact same fitting with all engines. So check out the recommended plug size for your marine engine before you make your purchase.

  • Decent heat resistance
  • Comes gapped
  • Easy to plug in and install
  • Great for marine vehicles
  • Decent for Johnson Outboard engines
  • A bit on the pricier side
  • You might get iridium core plugs for this price


Buying Guide

How To Install New Spark Plugs In Your Marine Outboard

Don’t just go out and buy whatever plug you see. Here are a few factors that you should consider before picking a spark plug for your boat engine.

Core Type Matter

The core material is one of the main things you must consider before picking up a spark plug. The most common ones are copper cores. And you can get iridium or platinum cores on the market too.

Unlike copper-cored plugs, iridium and platinum are harder. They are also priced way higher than the copper ones. So if you’re focusing on budget, you can do just fine with the copper core.

And if you truly want more longevity, iridium or platinum are the two ways to go.

Don’t Burn a Hole in Your Pocket

The price of spark plugs is important. Most of the copper plugs won’t cost you north of a couple of dollars. So you can stock up on 4-packs and 10-packs easily.

But the iridium and platinum plugs are expensive, and you have to be super sure whether you want that or not. Usually, if you’re using your boat almost every week, you could invest in the more expensive ones.

Not All Plugs Will Fit

The last thing you should know is that there are different-sized spark plugs. So it’s normal that one spark plug that fits in your truck engine might not fit in your boat engine.

Always look out for the manufacturer’s recommendations if you want the best of all worlds.


Champion 828M Pack of 4 Copper Marine Spark Plug

Do boats need special spark plugs?

Most boat engines are outboard motors or inboard/outboard motors. These types of engines use different spark plugs than a car engine. The reason for this is that boat engines are typically exposed to more water and moisture than car engines, so they need spark plugs that can withstand these conditions.

Boat engines also tend to run at higher speeds than car engines, so they need spark plugs that can handle the increased stress. In addition, boat engines are often used in saltwater, which can corrode standard spark plugs. For these reasons, it’s important to use the correct type of spark plug in your boat engine.

Can I use spark plugs of any size?

No, usually, the sizes of the threads of spark plugs are denoted in the model numbers. So you can’t use just any size for your boat.

Is it okay if I use any branded spark plug?

The only thing that should matter is your boat engine’s design. Copper plugs are great for conductivity, and you might not get much longevity. But iridium spark plugs are expensive, although they might last you longer.

Which plugs are best for longevity?

If you’re looking for longer life than platinum and iridium spark plugs are better. But that’s not to say that copper plugs aren’t durable. They are just not as durable as the other two. But I think the value you get out of copper is commendable.

What is the difference between a marine spark plug and a regular spark plug?

The most important difference between marine spark plugs and regular spark plugs is the material they are made from. Marine spark plugs are made from a special material that can withstand the corrosive effects of salt water. Regular spark plugs are not made from this special material and will corrode quickly when exposed to salt water. This can cause serious engine damage.

Should I get iridium or platinum spark plugs?

Spark Plug Outboard Plug

Iridium spark plugs are said to offer better performance than platinum spark plugs. They have a smaller electrode tip that is said to improve ignitability, fuel economy and emissions. Platinum spark plugs, on the other hand, have a longer lifespan than iridium spark plugs.


That’s it from us. You should probably have a clear idea about the best marine spark plugs for your boat. We’ve talked about the top six after shuffling through a lot of them.

All of these serve the same purpose. But some of them offer one or two gimmicky features that you might never need. You need to be aware of the money that you’re spending to put a replacement spark plug into your engine bay.

On top of that, don’t forget to check out all the features and compare them. Only spend your hard-earned bucks on something you think is value for money. Good luck with your ride on the ocean, but don’t forget to stay safe.

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