EFI Engines and Spark Plugs

[biffdotorg]

Ok, so I am noticing a trend on here that guys are replacing spark plugs annually on current 4-stroke EFI engines. Spark plugs are not overly expensive, but I am one to question the norm if I don't see immediate benefit.

A bit of background, I come from a bit of a motorsport, toy collecting background, so my experience comes from that of many brands and not just this one boat.

In the past, 2-stroke snowmobiles required us to carry a second set of new plugs, pre-gapped, as they could foul at any time. And you had to be prepared to swap them trail side. You knew when a plug fouled, as it would run rough, or rough start etc. To this day, carbed Yamaha sleds and Waverunners would require at least annual replacement as they would foul usually after the first couple tanks of gas as we ran out the fuel stabilizer.

So after 2 Carbed 2-stroke Yamaha snowmobiles and 3-carbed Yamaha Waverunners, I am 100% EFI 2-stroke Waverunners, and EFI 4-stroke sleds. And the annual swap of spark plugs is not as prevalent. Meaning, I swapped them on our GP 1300r's, but the difference was just a bit noticeable. EFI just really does keep the engine from fouling those plugs unlike before.

My four stroke sleds are still running the factory plugs! And this includes 5 different sleds with over 30,000 miles total!!

My previous 2-stroke EFI boat ran the factory plugs for around 100hrs until I swapped them as I had noticed one finally fouled. And that engine ran like a top all the way up until that time.

My motorcycle uses iridium tipped plugs like my truck, and it has over 33,000 miles on it, and it may just be coming up on the interval to swap them.

So that long story comes to the current boat. Twin 1.8ltr EFI four strokes. The manual lists checking the plugs for fouling and gap, but not replacement. But the need to replace these plugs is just not there, let alone annually. Can anyone on here truly tell me they noticed a degradation in performance by not changing them annually? And better yet, did you notice any performance gain by replacing them?

I have a full set sitting on my bench, pre-gapped. But I see no real reason to put them in. Maybe next summer after I work the stabilizer out of the tank of gas. But these engines just don't fry plugs like the old ones.

Opinions welcome. And if someone comes back with, "its cheap insurance" I will pre-comment with, "that is a fool spending money on insurance for a plug failing, that is far from catastrophic failure"

Thanks everyone

 

[bumpy]

Probably the biggest benefit is making sure that they aren't stuck/corroded. You get that with the gap check, so I can see your point!

 

[Zizzou 192]

The 2 spark plug problems on the 1.8's are as follows:

The plugs seize in place...which can be prevented by applying the appropriate Permatex Anti-Seize

Old spark plugs [used for more than one season ] seem to greatly reduce [ up to 10 or more mph ]. I did not believe this was possible, but I have experienced it. Dealer said upon purchase if boat was getting slow and you've already checked the clean out port and impeller, change the spark plugs. I guess he wasn't kidding.

There is a sevice chart in I believe in the boat operator's manual that displays frequency intervals of maintenance including spark plug changes.

 

[Matt Phillips]

I too have changed mine annually. Last year the dealer removed them and said they looked fine and reinstalled. That was with about 80hrs on them. I still changed them out this spring out of habit. I too have been debating about swapping them out and will likely do so again in the spring after running the first tank through them.

One benefit of changing them out annually besides not having them seize is that you know they are good to go all season. For me, for the price of a set of plugs annually, not having to spend 30-60 minutes on a day on the water swapping them out is worth it.

 

[sapperfitz]

I agree with you that spark plugs in a 4-stroke EFI motor should last for hundreds of hours. But...... At 18 total hrs. my port engine began running rough and surging in the mid-RPM range. I checked my impeller, checked the fuel filter, and made sure I had fresh gas to no avail. I decided to pull the plugs and they looked brand new and were gapped properly; I replaced them anyway and the engine ran fine afterwards. I did not replace the starboard plugs at that time and my starboard engine began showing the same symptoms at 38 hours. Those plugs looked brand new, also. It is disappointing that I went through plugs so quickly, but new plugs fixed the problem on both engines.

 

[swatski]

I change mine every 50 hrs or so, never had any issues. No anti-seize.

The MR-1s, which are 4stroke and EFI, have been documented over and over and over to have plug changes cure an impressive array of issues...!
1.8s - not so much but enough to make it worth it for me to stay proactive.

—

 

[biffdotorg]

Thanks guys, that's what I wanted to hear. Since we have a forecast for snow next week, I think I will save my fresh set of plugs for tank #2 of fuel next summer. It's a sad day in our household as the boat and two waverunners are sitting in the garage and driveway waiting for their time with the foam cannon and buffer. All to be winterized and put away for the season.

Like every fall, we are in denial that it's over till the first freeze or snow. This is a bit early this year. Famous last words, "there will be another warm fall weekend" and then I am towing the boat to storage with slush on the highway hitting my clean boat before bed time. GRRRR.

 

[Neutron]

Your average 1.8l is cruising at 6k rpms or better which is double if not more than double the rpm of your average automobile engine at cruise. My truck cruises at 60 to 65mph at 2 grand.
So with knowing that, your average plug in your 1.8l boat is firing more than twice as much in the same amount of hours.

 

[Cobra Jet Steering LLC]

I add never seize on the plugs before ever running a 1800 engine as well as silicon grease on the coil boots. I use iridium plugs when the engines start running a little rough so that is normally every season or so and it does make a noticeable improvement.
I also have my own design for a ribbon delete.
I also add fuel injector cleaner every month.
Now I am repairing the damn nano hull leaks on both my skies again it just never ends.
Currently doing the intermediate bearings also.
Just finished one and hoping for the temperature to cool down a little before I do the second one. Getting heat stroke working in the 92 degree heat out in the sun all day .
I need to invent a padded shirt for leaning inside jet skies when working on them. I put swim noodles on the edges but those didn't last very long , my bruises have bruises.

 

[biffdotorg]

Your average 1.8l is cruising at 6k rpms or better which is double if not more than double the rpm of your average automobile engine at cruise. My truck cruises at 60 to 65mph at 2 grand.
So with knowing that, your average plug in your 1.8l boat is firing more than twice as much in the same amount of hours.

That's a fair statement and something to consider. But my Yamaha 4-cylinder 996cc engines are running 10,000RPM in crazy conditions and running on the factory set of plugs. One ran over 12,000 miles before I replaced it with my current sled, and it has around 7,000 miles on the same engine that turns the same RPM. Keep in mind I didn't replace them due to the engine even showing wear. But 12K on a sled is unheard of in the two stroke world. I would have changed the plugs, but it's a serious pain.

As Jeff said above, Iridium tipped plugs have more life as well. My bike is a V-twin that runs around 4-5K RPM and has over 33K miles on it. It's probably due for plugs, but you wouldn't know it. This is really what I base my question on more than a comparison to a car.

It's really not as bad as the oil debate, but everyone has their own experience. Since my 242 has come to me putting out 40+ mph, but hearing that they can push 50mph, I think plugs may be the next step. As cavitation is not an issue.

Thanks again guys.