'98 115hp 2stroke Oil leak from spark plugs

[Jason2tpa]

1998 115hp 2 stroke oil injected

Bought this engine a few months ago, runs great and is in incredible condition for its age. However I recently noticed oil residue coming from each of the 4 spark plug holes. I do a lot of idling, keep in mind. And Ive read that idling for long periods of time can be the cause of this due to unburned fuel/oil in chamber. Today I took the boat out and for the first time i lost power at 3/4 throttle. Bogged down. I limped back to ramp. I havent replaced plugs since buying boat so I'll definitely do that. After I change the plugs and hopefully fixes the problem, what can be done in the future to prevent build up of oil on plugs from idling? I make it a point to run engine at WOT for a minute or two on way back to ramp. Other than that, suggestions? Where ya at rodbolt and boscoe!!

[99yam40]

I would be pulling the plugs to see what they look like before saying the plugs are what caused your problem

[boscoe99]

Check the oil control rod to make sure the linkage or linkage clip is not broken.

What brand of oil are you using?

If the primer ball is pumped when the motor starts to bog down does it get better, worse or stay the same? Could be a fuel pump not supplying enough gasoline at 3/4 throttle.

[Jason2tpa]

All 4 plugs were fouled pretty bad. 3 of 4 had burnt oil deposits near tip. Replaced all 4 and launched boat again. No issues starting or remaining on. Throttled up to 1/2 and power dropped off. It holds at 1/2 throttle fine but soon as i give more it does not accelerate. Using same brand of 2 stroke non synthetic oil ive had boat. I believe brand is quicksilver, or something sounds lije that. I'll have to check oil linkage once i pull boat out water.

I would be pulling the plugs to see what they look like before saying the plugs are what caused your problem

[rodbolt17]

the oil from the plugs
two causes
1 is they were never torqued correctly.
two is the crush ring,also called a fire ring,is only supposed to be crushed once

[Jason2tpa]

Primer bulb is same...i can feel flow going through it.

Check the oil control rod to make sure the linkage or linkage clip is not broken.

What brand of oil are you using?

If the primer ball is pumped when the motor starts to bog down does it get better, worse or stay the same? Could be a fuel pump not supplying enough gasoline at 3/4 throttle.

[Jason2tpa]

If anything the plugs were over tight. This engine has run perfectly since buying four months ago. But obviously the oil bleeding from plug holes is the sign of whatever is causing the loss of power. Can't be a coincidence, right? Ive recently done 2 things that would effect engine: filled the main oil tank and added a can of Seafoam, which ive used before wout problems.

the oil from the plugs
two causes
1 is they were never torqued correctly.
two is the crush ring,also called a fire ring,is only supposed to be crushed once

[99yam40]

What is inside the cylinders(compression,fuel,oil) should not be coming out around the plugs.
so I would not think it is related to the missing.

Check the fuel pumps, leaking diaphragms will over rich a cylinder by leaking into crankcase.

After decarboning using Seafoam they recommend changing the plugs as deposits tend to get deposited on them

Ive recently done 2 things that would effect engine: filled the main oil tank and added a can of Seafoam, which ive used before wout problems.

I hope you added the seafoam to the gas and not the oil tank

[boscoe99]

If anything the plugs were over tight. This engine has run perfectly since buying four months ago. But obviously the oil bleeding from plug holes is the sign of whatever is causing the loss of power. Can't be a coincidence, right? Ive recently done 2 things that would effect engine: filled the main oil tank and added a can of Seafoam, which ive used before wout problems.

Think about it. A properly torqued plug with a known good gasket has to keep high pressure within the cylinder from getting past the spark plug. If oil is getting past the plug then something is just not right with the seal of the spark plug.

Over tightening can be as bad as under tightening. Or worse. Is your torque wrench known to be calibrated properly? 18 pound-feet is not much.

Is the mating surface for the spark plug on the cylinder head clean and free of swarf and swill?

Hard to believe that all four plugs would have the exact same failure mode.

Capiche?

[Jason2tpa]

Agreed. There should not have been oil bleeding past seal. 2 of the 4 plugs had a build up of black corrosion on the electrode, the other 2 were black. So yah, all 4 were fouled in some manner. I recon this can be caused by plugs being both over tight and under tight?

Before installing the 4 new plugs, I cleaned the plug wells, mating surface, threads, and case cover. As earlier noted, I ran the motor again after installing the new plugs and could only get up to 30 rpm. Any more throttle I can hear it bog down, no acceleration. So brought the boat back in, trailered, lifted cowling and the case was still clean, though the motor was only running for maybe 15min.

Sounds as if y'all think the plug bleed is completely separate from the power loss, whereas I thought the two were linked. But you guys are the prof's, so I'll take your word over my amateur experience. The 3 necessities for a properly functioning motor, fuel, spark, compression. I've got spark, it can't be compression because I just ran the boat last night without any problem, and then there's fuel. I guess it could be fuel? I run the boat a lot, so always new fuel added. The primer bulb doesn't collapse when running, which tells me there is no fuel line obstruction between the tank and bulb. The motor operates up to 30 rpm for any length of time, so if the fuel pump wasn't working I couldn't get past 15 rpm for more than a few minutes before cutting off. I'm perplexed.

Think about it. A properly torqued plug with a known good gasket has to keep high pressure within the cylinder from getting past the spark plug. If oil is getting past the plug then something is just not right with the seal of the spark plug.

Over tightening can be as bad as under tightening. Or worse. Is your torque wrench known to be calibrated properly? 18 pound-feet is not much.

Is the mating surface for the spark plug on the cylinder head clean and free of swarf and swill?

Hard to believe that all four plugs would have the exact same failure mode.

Capiche?

[Jason2tpa]

99yam check out the reply to boscoe I just posted. Agree, no substance should bleed from the plugs. I guess the reason I think the two are linked is because of the poor plug condition. Figured once I throttled up, with that much fouling on the plugs, not enough spark was being provided to ignited the mix. So that's why I immediately thought it must be the plugs. But obviously not, cause with new plugs I'm still getting power loss past 30 rpm. Reply to your earlier...plugs changed after I added Seafoam, which was dumped in the FUEL tank about a week ago. I ran the engine immediately after using seafoam that day, and a few more days...no issue. Checked the fuel pump housing and connections...no signs of fuel leaking.

What is inside the cylinders(compression,fuel,oil) should not be coming out around the plugs.
so I would not think it is related to the missing.

Check the fuel pumps, leaking diaphragms will over rich a cylinder by leaking into crankcase.

After decarboning using Seafoam they recommend changing the plugs as deposits tend to get deposited on them




I hope you added the seafoam to the gas and not the oil tank

[Jason2tpa]

One more thing I can add, though I believe unrelated, but what the heck. I have a yamaha digital tachometer, which also has temp and oil indicators. Occasionally the screen will get haywire and no rpm can be seen. The digital readout do not resemble numbers, and there can sometimes be an arrow over either the temp or oil symbols. No alarms. If this haywire happens, it occurs a few minutes after firing up engine for the first time of the day. However, once at 1/2 to 3/4 throttle, if I knock my knuckle lightly on the screen, it displays normally.

Again, I don't think the power loss and this are related, but thought to mention just in case. Btw, does anyone know the digital screen inconsistently going haywire as I describe?

[zenoahphobic]

The oil bleed past the plug I would think is not uncommon. Yes it is the weakened seal, however all the two stroke plugs I have ever pulled all eventually have oil saturated threads, meaning air does pass this seal atleast (very little at each power pulse culminating). Not a major factor in degradation of performance though.

What I find a bit stupid is that the sparkplug washer can only be crushed once, but there is nowhere to buy these washers to replace them with! You technically have to replace the whole plug every time you remove them to inspect. Is this an opportunity to make millions by making and marketing these washers (seals)?

[rodbolt17]

I am old enough to remember when they were called fire rings and you could buy them at the parts store when you got your new points

we did not know much about them new fangled tapered seat plugs.

so ya think the compression is good just cause?

think again.
unlike 4 strokes that can develop marginal compression loss over time.
two strokes tend to just take a dump all at once.

test the compression,test the spark then fix the fuel system.
assume NOTHING.

Oscar and Felix did a skit explaining the word assume.

[99yam40]

I agree
test what you can to make sure and then play with the stuff you cannot test