Surprises during spark plug replacement

[Ronnie]

Found some time after work to change the plugs out before off season storage and found this:

1. oil on the top / coil side of cylinder 4 on the starboard engine. I think the seal between the valve cover and case is leaking. Hopefully only a $50 plus an hour of my labor fix.

2. the coil on cylinder 3 of the port engine is going bad/deteriorating. Need to source one of these but my local power sports shop cha get me charged me $240 for one a few years ago, after I got two DOA units off Amazon for $120ish. I had a spare but will need another coil anyway.

3. here are pics of the old plugs, based on the little I know about reading plugs I think the port engine is running lean.

the boat ran well all season but the port engine was burins oil a lot faster than the starboard engine.

I finished the job in 45 minutes, but have a few things to buy during the off season. Still I may bring it in for some talc/top end rebuild this off season.

 

[FSH 210 Sport]

Sorry to see you found surprises…. Hopefully you are able to source the parts quickly and the job is easy.

The port spark Plug in the picture looks pretty oily as well. The tip of the plugs insulator looks good, what does it look like down inside the plug? How many threads of heat is there are on the plugs?

 

[Cambo]

How many hours on the motor ?

for the coil look around for someone parting out a jet ski with the same motor.

 

[Cobra Jet Steering LLC]

Yes the valve cover gasket started leaking and oil filled the plug recess I had many a similar situation with Sea doo 4 tec engines . You probably do not need to find a coil once you fix the oil leak the plug hole will not fill with oil and as long as the coil fires the engine should run ok if you just put some dielectric grease on the plug base before sliding the coil on the plug just to be sure it is insulated I always use that regardless .

 

[Rodder77]

Looks like the wrong coil pack # for a 2010 yamaha 242? Double check it to be sure.... i see 6S5-82310-00-00 listed for a 2010 242, looks to be readily available online + ebay.

BTO Sports | Camarillo, CA | Motorcycles PWC ATV Utility Parts 2010 Yamaha

partsfinder.onlinemicrofiche.com

Ignition Coil for Yamaha 4-Stroke 1800 Wave Runner & Boat 6S5-82310-02-00

Bay Area Power Sports have been providing powersports products since 2005. One-Stop-Shop For ATV, Dirt Bike, PWC, Marine Parts and Accessories. Free Shipping. Shop online today and start saving!

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[David Martin]

4pcs Ignition Coil H6T11272 6S5-82310-00-00 6S58231000 for Yamaha Jet Ski boat | eBay

This is ebays version the price is for 4 coils not sure of the quality but who knows.

 

[Ronnie]

4pcs Ignition Coil H6T11272 6S5-82310-00-00 6S58231000 for Yamaha Jet Ski boat | eBay

This is ebays version the price is for 4 coils not sure of the quality but who knows.

@Rodder77

Thanks for the leads guys but having tried less expensive coils twice now I plan to buy my next coil from my local power sports shop or Yamaha dealer, they are expensive but so far always work (no DOA). I may buy a 4 pack from Amazon and text them out. If they work out keep them as spares.

 

[Ronnie]

Any thoughts on the plugs that came out of the engines recently. Recall that the 4th plug on the starboard engine is the one exposed to all the oil from the broken seal. The port engine burns about a quart of oil per weekend (2 days) on the water .

 

[Can0n11]

P2 plug has something going on there. Have you checked compression in your #2 cylinder? Just curious, what is the gap on those plugs?

 

[itsdgm]

Hey Ronnie. Make sure to set the new gasket in there with some “three bond”, especially on the camshaft end. Otherwise it can blow those tabs out and leak a lot of oil.

 

[Ronnie]

P2 plug has something going on there. Have you checked compression in your #2 cylinder? Just curious, what is the gap on those plugs?

Please elaborate? What do you see that have rise to your comment / question? I’m just trying to learn how to read spark plugs better.

interestingly, that plug is associated with a seal and coil failure that I experienced two seasons ago. Basically the seal failed on that cylinder and so did the coil along with the spark plug. When I first examined it the electrode of the plug was gone/ fell into the cylinder. I tested the compression on all of the cylinders and found that on to be 20% lower than the rest (120 psi instead of 150). I planned to have the tops ends of both engines rebuilt last off season but life happened/got in the way.

 

[tdonoughue]

All of them look pretty dark compared to what I usually see, so probably a sign of oil infiltration into the cylinder.

I see a difference in P2 as well. Note the insulator around the electrode going into the plug and compare that against the others. Most of the others are pretty white; P2 is pretty dark. Again, a sign that things are not burning completely. May be a very rich burn, but that is not likely with an ECU controlled engine (unless you get a stuck injector or something like that where it is probably much worse than this). Given the very dark color and the oil on the coils and the burning oil issue, I would bet your head has a leak letting oil not only onto the exterior of the coil, but also into the cylinder.

Therefore, I agree with the compression test. Bet you find at least #2 is leaking some.

 

[Ronnie]

Well, based on the feedback I’ve gotten so far and what i know about the engines, I either put the boat into storage early or at just the right time. Meaning, I plan to have the top ends rebuilt, at least on the port engine. Just not sure if I want to do that now or when when the material / shipping problems caused by Covid are not so bad. The last thing I want is to have the boat partially disassembled next summer waiting on parts, especially since it’s been running fine (just a little loss in rpms/performance) since I replaced the coil and seal. To be fair, I check and top off the oil on that engine every time I take the boat out, it can be a hassle but acceptable too me, so far anyway.

my next steps will be to run another compression test on both engines, before reaching out to the shop with the results and pics for their feedback. I still plan to order the seals/gasket and a coil as well.

thanks for all the feedback everyone.