Intermittent start issues on single engine only

[FLJetBoater]

How likely is it that a spark plug failure would cause an engine not to start? I’m not a mechanic but I would have thought that just that cylinder wouldn’t fire but the other 3 would? Seems strange that fairly new spark plugs would have multiple failures. Or I’m wrong and just 1 bad plug would cause this? Either way guess what’s going in the toolbox now….full set of spare plugs.

this came up tonight because my starboard engine wouldn’t start for our last leg home after being on the water all day. Limped back.

This is what it sounded like

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pulled a liter of oil out and it was a bit dark but no water or anything in it.

changed spark plugs….here’s the old ones



theyve only got MAYBE 10 hours on them I just changed them last week.

put new ones in and it fired right up.

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[captainhook]

I experienced this before as well. These motors are pretty hard on plugs for whatever reason. Many change them annually. I’ve gotten away from that now but I change them whenever starting takes an extended amount of time. I also have a theory that Stabil fouls them earlier as well if you’ve used that.

 

[captainhook]

Also, the ones I’ve pulled that either won’t allow it to start or take a long time to start don’t appear bad visually either, they look fine.

 

[FLJetBoater]

Also, the ones I’ve pulled that either won’t allow it to start or take a long time to start don’t appear bad visually either, they look fine.

Never used stabil……just baffled that one would have went bad so quickly

 

[FSH 210 Sport]

Never used stabil……just baffled that one would have went bad so quickly

Another member with TR-1s just did a plug change along with oil and air filters and now his motors wont rev up as high, a small amount but still. It can only be the plugs as everything else checks out… do you by any chance have the old ones?

I’m fascinated by this whole plug thing… I wonder what is happening to make these engines be so finicky about plugs..

 

[RobbieO]

Another member with TR-1s just did a plug change along with oil and air filters and now his motors wont rev up as high, a small amount but still. It can only be the plugs as everything else checks out… do you by any chance have the old ones?

I’m fascinated by this whole plug thing… I wonder what is happening to make these engines be so finicky about plugs..

I would make sure you are using the recommended plugs. Internal resistance of the plug can be different. And the length and gap matters as well. Make sure they have the same reach.

 

[FLJetBoater]

Also, the ones I’ve pulled that either won’t allow it to start or take a long time to start don’t appear bad visually either, they look fine.

Another member with TR-1s just did a plug change along with oil and air filters and now his motors wont rev up as high, a small amount but still. It can only be the plugs as everything else checks out… do you by any chance have the old ones?

I’m fascinated by this whole plug thing… I wonder what is happening to make these engines be so finicky about plugs..

yes I kept the plugs. I was considering getting them tested to satisfy my own curiosity if one actually failed…I had them in order by cylinder but afterwards I was so happy it started i started cleaning up and I picked them all up in one hand so they’re mixed up now

 

[FLJetBoater]

I would make sure you are using the recommended plugs. Internal resistance of the plug can be different. And the length and gap matters as well. Make sure they have the same reach.

They are absolutely the correct plug. I know because when I go to get them from autozone they always tell me that they have about 1500 in stock lol. The autozone I go to supplies SBT.
And I always double check the boxes for the 6668 code

 

[fatboyroy]

I’d check the cylinder that the bottom plug go to, seems it’s more fouled than the other 3.

 

[RobbieO]

They are absolutely the correct plug. I know because when I go to get them from autozone they always tell me that they have about 1500 in stock lol. The autozone I go to supplies SBT.
And I always double check the boxes for the 6668 code

That's good info. Napa and O'Reillys have to order them.

 

[FLJetBoater]

I’d check the cylinder that the bottom plug go to, seems it’s more fouled than the other 3.

They’re cylinder 1-4 top to bottom. I’ll have to find someone to look I don’t have a scope or other tools for that

 

[FLJetBoater]

I’d check the cylinder that the bottom plug go to, seems it’s more fouled than the other 3.

Is it possible that overfilling oil could cause a plug to foul like that? For the last oil change a few weeks ago I did it on the water. Removed about 3.5q of oil but when I refilled it I had to almost put a full 4 quarts in to get it midway between low and high on the stick. It felt to me like I was putting too much in but the dipstick said otherwise. Engine compartment is clean as a whistle nothing is leaking.

 

[fatboyroy]

Is it possible that overfilling oil could cause a plug to foul like that? For the last oil change a few weeks ago I did it on the water. Removed about 3.5q of oil but when I refilled it I had to almost put a full 4 quarts in to get it midway between low and high on the stick. It felt to me like I was putting too much in but the dipstick said otherwise. Engine compartment is clean as a whistle nothing is leaking.

when I do my oil change I level the engine and I get almost 4 quart out and put the same amount In and dipstick measure correctly. Since it’s #4 cylinder when u are on plane i would think it will be the lowest cylinder since bow always higher than stern while running But I do not know how oil is pumped to the cylinder and I am not a mechanic so I can’t comment if it makes any difference (if oil would go to cylinder with lowest elevation). try to level the boat and measure oil level maybe? Another idea is to check if fuel injector is giving too much gas in that cyclinder to foul it?

 

[tdonoughue]

I would not only check that cylinder (compression test would be a start), but I would check the gap on the plugs. A little gap difference (like if they got dropped in shipping or putting them in or something) could cause a quick issue like that.

Overfilling usually causes issue with oil splashing up onto the air filter, which then chokes out the engine. Not really involved in the spark plugs...

 

[FLJetBoater]

I would not only check that cylinder (compression test would be a start), but I would check the gap on the plugs. A little gap difference (like if they got dropped in shipping or putting them in or something) could cause a quick issue like that.

Overfilling usually causes issue with oil splashing up onto the air filter, which then chokes out the engine. Not really involved in the spark plugs...

Thanks. I checked gap on them and they were all ok.

I get every other service done at the dealer so I will ask them to look into it based on what the spark plugs look like when I bring it in for next one.

 

[David Martin]

Those plugs look clean......10 hours.........gives me a head ache. She was firing/stumbling. Put in new plugs and she if she runs, I would CARRY a can of starting fluid in boat ........Starting fluid is always helpful in diagnosing Spark or fuel problems. What keeps 4 injectors from getting fuel....heat soak vapor lock/computer ECM. Lets not forget Lanyard engine cut off switch a single switch with 4 wires 2 wires for each engine one a ground. Corroded wires on one side of switch giving you intermittent fire........ I also read on this form about clean out hatch switch being a 2 part switch, one half shuts down starter the other half shutting off the ignition. Head starting to spin now......

I always keep a can of starting fluid on board with my tool kit to pull plugs just for these head ache moments. Good Luck

 

[FLJetBoater]

Those plugs look clean......10 hours.........gives me a head ache. She was firing/stumbling. Put in new plugs and she if she runs, I would CARRY a can of starting fluid in boat ........Starting fluid is always helpful in diagnosing Spark or fuel problems. What keeps 4 injectors from getting fuel....heat soak vapor lock/computer ECM. Lets not forget Lanyard engine cut off switch a single switch with 4 wires 2 wires for each engine one a ground. Corroded wires on one side of switch giving you intermittent fire........ I also read on this form about clean out hatch switch being a 2 part switch, one half shuts down starter the other half shutting off the ignition. Head starting to spin now......

I always keep a can of starting fluid on board with my tool kit to pull plugs just for these head ache moments. Good Luck

What’s interesting that I didn’t know, but on these 2020s the lanyard actually stops engine from turning whereas on older models it would just kill fuel/spark.
That was actually one thing I tried…

 

[Ronnie]

I had a coil disintegrate on one of my engines a few seasons ago. The my mechanic friends and some members here think that I cracked the related plug installing it. The seal of the valve cover broke on the cylinder of the failed coil. This caused a lot of hot oil be sprayed onto the coil that failed.

my point is that this plug totally failed, as in the electrode that was in the ceramic of the plug broke off and slid into the cylinder. The engine was hard to start, ran rough, only spun up to 6k v 7,600 rpm at wot and would often die at idle, but it ran good to enough for the two days of tubing.

I did a compression check afterwards and found the cylinder with the failed plug read about 20% lower than the other plugs in the engine.

 

[FLJetBoater]

I had a coil disintegrate on one of my engines a few seasons ago. The my mechanic friends and some members here think that I cracked the related plug installing it. The seal of the valve cover broke on the cylinder of the failed coil. This caused a lot of hot oil be sprayed onto the coil that failed.

my point is that this plug totally failed, as in the electrode that was in the ceramic of the plug broke off and slid into the cylinder. The engine was hard to start, ran rough, only spun up to 6k v 7,600 rpm at wot and would often die at idle, but it ran good to enough for the two days of tubing.

I did a compression check afterwards and found the cylinder with the failed plug read about 20% lower than the other plugs in the engine.

See that’s what frightens me. You had a plug completely fail and the engine still started but just ran rough. Mine would not start at all. Hoping that replacing the plugs didn’t just mask something else

 

[1WetBoat]

These spark plugs, unlike car/truck plugs, usually operate for long periods of time at higher RPM's so the beating they take is crazy.
Not to go in a different direction but check to make sure the wiring harness on the plug coils isn't lose or anything like that. Heck, I would also check the Fuel injector harness connectors. While changing out to new plugs those could have been moved and that "fixed" your starting issues. Just something else to look at because I don't think 1 bad plug will prevent your engine from starting.