Sea Doo RXP Spark Plugs Removed

HowTo: Sea Doo Running Rough? Change the Spark Plugs First 28

2006 Sea Doo RXPI had one of my 2006 Sea Doo RXPs out on the lake last weekend, when I noticed it was running kind of rough. The engine didn’t sound right, and it felt low on power. Every now and then, I’d get a burst of full power, but then lose it again. Those are classic signs of not running on all cylinders — and on a three cylinder craft, that’s no good.

If this same problem is happening to you, don’t drive to the Sea Doo dealer with your wallet open just yet. You can save yourself a lot of time and money by simply replacing your spark plugs. Changing the spark plugs on a Sea Doo is fast, cheap, and even if you’ve never changed a spark plug on anything ever before, you’ll be able to do this — all by yourself — by following this simple guide.

Toos & Supplies You’ll Need:

  • A 5/8″ spark plug socket (around $9 for a nice one, but you may already have one in your tool kit)
  • A ratchet and at least one socket extender (you probably already have this in your toolbox)
  • Some dielectric grease or compound ($8 for a tube that will last you a long time)
  • Some anti-seize lubricant ($8 for a bottle that will last you a really long time)
  • OEM-recomended spark plugs (mine were under $3 each at a local auto parts store)
  • A spark plug gapping tool ($1-2 at a local parts store)
  • A shop rag

As far as the spark plug wrench or socket goes, you may already have one in your tool box, and hopefully it’s the right size. Spark plugs are either 13/16″ or 5/8″. On the 2006 Sea Doo RXP (and probably most other Sea Doos), you’ll need a 5/8″ socket. You can find them sockets for on Amazon, and if you’re feeling really fancy, you can even opt for one that’s magnetic.

Because the spark plugs are down inside the engine block, you’ll need an extended spark plug socket, and/or a socket extender on your ratchet. I use a standard size socket with an extender.

Any hardware or auto parts store will have dielectric grease. I’m a fan of Permatex brand. It’s especially useful in watercraft applications, as it helps prevent electrical connections from corroding. You can buy a large tube, or individual use packets. I like to be generous with the stuff, and it stores for a long time, so a large tube isn’t a bad idea. You may want to try some Dow Molykote (also called Compound 111). It’s a grey substance that’s thicker than dielectric grease, but serves the same purpose. BRP uses it at the factory on the rubber spark plug caps (you’ll see it when you take the caps off to access the plugs).

Anti-seize lubricant is also a must. It’s about $16 for a large bottle on Amazon, but you can use it on lots of stuff, and it lasts forever. Any time you’re joining two pieces of metal that you’ll later want to un-join, and especially if they are made of two different metals (like screwing a steel spark plug into an aluminum Sea Doo engine block), you need to use this stuff.

As far as which spark plugs to get, you’ll hear a lot of advice about iridium plugs, or high-tech blah blah plugs. But the truth is that the cheapo OEM-recommended plugs work the best, last just as long as any of the exotic plugs, and are a fraction of the price. Any of the Sea Doo 4-tec engines (on the RXP, RXT, GTI, or GTX) use the NGK DCPR8E plugs (also referred to as NGK part 4339). They’re about $3.70 each on Amazon (which is so cheap that they’re only available as an “add-on” item if you’re ordering something else, since shipping would be more expensive than the plug). I ended up buying a box of 12 from O’Reilly Auto Parts for around $3 each. They don’t go bad, and you’ll be glad you have extra when you need them (I actually keep one in the on-board tool kit). Be careful not to buy the DCPR8E “Solid” plugs. You need the ones with the threaded cap, and you’ll need to remove that cap before you install them.

Getting Started

Once you have all your parts and tools handy, remove the seat to expose the engine bay. I’ve found this procedure is easiest if you’re on the port side of the boat. Before touching anything, make sure you don’t have a key attached to the ignition. If it makes you feel better, you can disconnect the battery, but as long as you don’t have the key attached, you’ll be fine.

First, pull out the oil dipstick and place it down somewhere clean. The dipstick is attached to the smaller yellow plastic ring handle in this photo:

Sea Doo 4-tec Engine Bay

Sea Doo 4-tec Engine Bay

Next, use your fingers to depress two tabs (one the left and right of the engine cover) and then pull the cover upward to remove. I like to place the cover face down on a towel on my dock when I do this, then I can store removed parts inside the cover like a dish.

Before you move on to disconnecting stuff, I recommend doing all the steps necessary to change a plug one plug at a time, and then move on to the 2nd and 3rd plugs, especially if this is your first time performing a plug change on your Sea Doo.

Remove the Rubber Spark Plug Cap / Ignition Coil

You’ll see a quick-connect attached to each of the rubber spark plug caps (also called a “coil stick” or “ignition coil”). Use your thumb to release the connector, pull it out of the spark plug cap, and move it out of the way. Grab the top of the rubber cap and rotate it back and forth while also pulling upwards. It should pull out without much resistance. Carefully set it down somewhere clean (inside the engine cover works for me).

FYI – if any of the rubber pieces are worn and/or need replacing, the part numbers you need are 420664020 for the whole ignition coil assembly and 420460830 for just the rubber boot / sealing cup.

Remove the Old Spark Plug

There’s actually a proper sized spark plug wrench in your on-board tool kit which will work, but I find it easier to use a ratchet and socket, especially if you encounter resistance. Use your 5/8″ spark plug socket and ratchet to apply gentle counter-clockwise pressure to unscrew the spark plug (remember: righty-tighty, lefty-loosey). The plug should remove rather easily, but if the current set of plugs weren’t installed using anti-seize lubricant, there could be a fair amount of resistance. It’s OK to push/pull your ratchet handle with some smooth force, but be very careful not to apply too much force. The plug threads are made of steel, while the engine block is softer aluminum, so don’t damage your block by cranking away on a stuck plug. If it’s really stuck, auto parts stores sell a product called PB Blaster that you can spray down the hole, wait a while while it loosens things, and then give it another go. If it’s still too hard to remove, your best bet is to take it to the shop, which is cheaper than a damaged engine block.

Here’s what my engine looked like while removing the plugs:

Sea Doo RXP Spark Plug Removal

Sea Doo RXP Spark Plug Removal

Once the plug is loosened all the way, you can use the rubber spark plug cap to press down in the hole, grab the top of the plug, and pull it out. The bottom of the plug will probably appear dark, and when it’s too dark that’s called being “fouled.” Here’s what a well used plug looks like once removed:

Fouled DCPR8E Spark Plug

Fouled DCPR8E Spark Plug

Throw away your old plugs one they’re removed.

Prepare the New Spark Plug

To prepare your new spark plug for installation, you’ll need to do three things:

  1. Remove the threaded cap
  2. Set the proper gap
  3. Coat the large threads with anti-seize lubricant

Removing the small silver threaded cap on top of the plug is easy. If it doesn’t just come off by hand, you can use one or two sets of pliers to help do the job. Discard the small metal cap, leaving just the exposed threaded post.

Next, your DCPR8E spark plugs should be gapped to a width of approximately .030 (inches). Out of the box, the gaps on mine were too small. Grab your spark plug gapping tool and slide the smallest part of the tool into the gap, then rotate the tool until the prong is at the .030 position. If your gap was too wide to start with, gently press down on the bottom end of the plug to reduce the gap, then use the gapping tool to set the proper width.

The final plug prep step is to evenly apply a coat of anti-seize lubricant to the larger bottom threads (not the smaller threaded post up top) to make them easy to remove the next time you need to change them. Make sure the threads are covered, but don’t go crazy and use too much. A nice, thin, even coat works best.

Install the New Plug

To help put the new plug down into the engine block, use the rubber spark plug cap to “grab” the top of the plug and lower it down into the hole, give it a couple gentle turns to start it threading, pull out the rubber cap, then use your spark plug wrench to tighten the rest of the way. I like to initially tighten just past “snug” to crush the spark plug washer, back it out a bit, and then re-tighten it down all the way to seat it properly. The factory spec torque is 17 ft-lbs, but I don’t use a torque wrench. Just make sure they’re in nice and tight, without over-doing it. You are going to want to get these out again some day.

Grease and Re-Install the Spark Plug Cap

Break out your dielectric grease or compound, and apply liberally to the top part of the rubber spark plug cap’s shaft, as shown here (credit to Dr. Doo on

Put dielectric grease on the rubber shaft

Put dielectric grease on the rubber shaft

This helps seal out water and gunk from getting down into the spark plug hole. You should also apply a glob on the bottom of the cap, inside the hole that covers and connects to the spark plug.

Push the spark plug cap back down into the hole, on top of the new spark plug. Wiggle it gently back down into place, and then turn it so the connector is facing the right way. Put another dab of dielectric grease on female side of the connector, and reconnect the wire.

Replace the Engine Cover and Dip Stick

Once you’ve repeated the above steps and replaced all three plugs, replace the engine cover by snapping it down into position, wipe any debris from the dipstick with a shop rag, then re-insert it into the engine. Replace the seat, and you’re done!

Go for a Test Ride

Now all that’s left is to take your baby out on the water, warm it up a bit, then open it up wide. You should have full power with all three cylinders firing strong. You’ll also have a huge grin on your face, knowing you now know how to fix the #1 most common cause of PWC misfires and loss of power — at a fraction of the cost the shop would have charged you.

And the next time your Sea Doo engine starts running rough, you’ll know exactly what to do, and you’ll probably able to do it in half the time.

If you have suggestions, feedback, or questions, please leave them in the comments below. And I invite you to check out my other Sea Doo related posts while you’re here!

Further Reading:




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  • Marcelo

    Steve, amazing details how-to!!! Thanks for your time in explaining this for people like me. The only question I have is regarding the “Remove the threaded cap”. Do I just pull from it and should be gone? Is this mandatory? Why do we need to do that? I read Doctor Doo’s article and didn’t say anything about it so that is why I’m asking. Thanks in advace!!!

    • Removing it makes the coils fit properly, and it’s what the factory does — I know because they were removed when I changed the original plugs.

      Not sure why the Dr. Doo article neglected to mention it, but it is the standard procedure on the 4-tec engines.

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  • Joseph

    Steve you were dead on for my 2011speedster w supercharger which only had 36hrs on it. Next maintenance was scheduled for 50hrs. I was terrified that the supercharger had gone bad. three fried sparkplugs n 12$ later the Beast is Back! Guess i will be checking plugs every 20hrs from now on. Thank You!

    • Great to hear, Joseph! I always keep a spare set of plugs in the toolkit. Happy riding! 🙂

  • Dustin

    i have a error code on my seadoo speedster 150 215 hp supercharged…error is P0352 for ignition coil #2…i changed the spark plugs and took it back out…ran fine for 5 mins then did it again…so i switched coil 2 and coil 3 to see if the code would change and it didnt so i changed it back….after changing it back it ran good for a few mins then did it again. Is this the ignition coil #2 issue or wiring issue to the coil? havent purchased a new coil yet and our seadoo dealer here only will work on seadoo PWC…they say they dont have the program to hook to my boat?? not sure what that means…any help would be appreciated…thank you

  • Jim J

    Hey Steve! Great article!

    I noticed the rubber seal at the top of my spark plug cap (it’s almost like a boot that fits around the spark plug shaft) is getting kinda deformed.. so I’m concerned it may not make a proper seal when i put it back into the spark plug hole.

    Have you ever seen if it’s possible to just buy this rubber seal somewhere? On bombardier’s site it looks like you have to buy the whole spark plug cap/ignition coil assembly. ugh…

    Or do you think just a liberal about of that dielectric grease will do the trick to ensure a seal, even if the rubber is a little deformed….

    grateful for your advice…

    • If it were me, I’d pile on the dialectric silicone and ride. 🙂

      • Jim J

        Thanks Steve will do LOL!!!

        After a lot of research however, I did find that the part I need. It’s called a “sealing cup”.

        And for some reason, it’s not actually listed on the parts manuals for my 2003 GTX 4-Tec seadoo.. but it’s listed on some later years models. Sounds like the plug coils/spark plug cap are the same for most 2002-2012 units so I’m told the sealing cup will fit my model. I hope the folks I talked to know their stuff!!

        Anyhow, it’s BRP part number 420460830. And it fits the plug coil in my earlier post (which was part no 420664020). Hope this helps someone else searching this blog down the road 🙂

        I won’t have the part in time for vacation, but oh well, I’m sure the dielectric grease will keep everything sealed for this summer! 🙂 Thanks again for your advice and great article.

        • Thanks, Jim. I’ve edited the article to include both part numbers!

  • fabrizio

    Steve, I rode my 2007 sea foo rxp 155 for the first time the other day, after a few minutes a noticed i lost power. it usually goes 50 mph, it dropped to 20 mph. no warning mights, no rough riding, no noises…..just half of power. what do you think?

    • I think you’ve got a perfect example to prove me right! 🙂 Sounds like you’ve lost at least one cylinder. Change the plugs and see what happens! It’s the cheapest first step.

      • Travis

        What would you check next if the plugs don’t cure the problem?

        • Hmm – bummer that didn’t fix it. If you’re losing power, then it’s probably one cylinder that’s not firing. The basic troubleshooting for engines is gas, spark, air. Changing the spark plugs usually helps with “spark,” but it’s possible that the connector is corroded, or something else is causing a spark problem. Gas could also be somewhere to look, as it’s possible you could have a clogged injector. Air usually isn’t the issue.

  • Ben

    Very helpful post. We just changed the 3 plugs on our 2008 Sea Doo RXT and it went from acting sluggish and topping out around 40 mph back to powerful speed at over 60 mph. I took the jet ski to 2 repair shops when it was riding slow and neither of them mentioned changing the plugs. We did end up having the wear ring replaced (which was needed) but the plugs ended up being the magic trick!!

    • Sigh. Crazy that two repair shops couldn’t figure it out, but good job on the DIY fix!

  • Hi, Sid. I’m a Western Australian living in the US! 🙂 The ECU sends the signals to the injectors, so if you’re sure the injectors are find, you should check the wiring to the injectors or the ECU (I’d suspect the wiring over the ECU). Also, if you’re wrenching by yourself far from a dealer, you should really join the forums. I think you’d benefit, and possibly meet some other WA-based Sea-Doo guys!

  • Buzzing sound…. hmmm…. without hearing it myself it’s hard to diagnose. But just like the article says, I always replace plugs first and see if that helps. If the oil light came on, that makes me wonder about the oil levels. Have you checked them?

    • Mahendra

      Yes I have checked the oil levels and changed the plugs. I have used the 10-30. The light is just flashing not solid and the sound is more like a beeping sound.

      • Nope, that’s a new one on me! I’d try asking over on the Sea-Doo forums. I bet someone over there has encountered this before (I hang out over there, too).

  • Hi, Mark. That could be a number of things, but it doesn’t sound like the spark plugs. I’d try asking your question on — lots of guys there with much more Sea Doo wrench experience with those newer models, and I’ll be they can help.

  • Jim Makepeace

    Steve, great article. The step by step is good but what’s great is that you give people the confidence to do this fairly simple repair. Thanks for whatever effort you put into this site.

  • Grant

    My 2004 sea doo keeps fowling one plug and messing up the electrodes an ain’t firing on one cylinder help me!!!!! Please!!!!!
    Ive changed all the plugs regular there’s no Water in the gas I’m ylost on what to try now

    • Hi, Grant. It’s hard to troubleshoot remotely, but my best suggestion is to check out in the technical forums. Those guys can walk you through anything. 🙂

  • Hi, Aaron. It sounds like the clamps inside the boot aren’t tight enough. Are you running factory-recommended spark plugs? I guess it’s possible that aftermarket ones might be SLIGHTLY too small… but that’s a long shot. If you’ve already replaced the coils and greased it up (which is also what I would have tried), the only thing left is to CAREFULLY squeeze the clamps inside the boot for a more snug fit.

    Or maybe you just ride too aggressive? 😉 Nah… no such thing! 🙂

  • Joe

    I have a 2007 Seadoo GTX with 92 hrs on it. Engine running rough and code P0326 coming up. Speed varies between full and 50%. Any suggestions??? Thanks, Joe.