Fouling spark plugs

[WinnerCougar74]

Thanks dingbat. That is very helpful. So far no one with a Chrysler outboard has posted their own experiences on this thread. I wonder if this is a problem with Chrysler outboards.

 

[racerone]

I rebuilt these motors myself.----Nothing to it at all.-----Bin working on Johnson / Evinrude / Mercury and the odd Chrysler since 1968.----All I can say is that the operation of 2 strokes , the mixing of gas and oil is not well understood !!

 

[WinnerCougar74]

It seems like you understand it. Thanks for sharing what you know. Does compression being down by 15-20 psi cause problems with these 2 stroke motors? (a commonly reported thing) Also, does the recirculation/puddling systems on these motors cause performance issues?

 

[WinnerCougar74]

I have been thinking about hooking up a vacuum meter to the tube that connects the 2 carbs to see if I can tweak the tune like you would with a 4 stroke.

 

[foodfisher]

It seems like you understand it. Thanks for sharing what you know. Does compression being down by 15-20 psi cause problems with these 2 stroke motors? (a commonly reported thing) Also, does the recirculation/puddling systems on these motors cause performance issues?

Been following force/chrysler forum for years. Surface gap plugs trolled for extended times will foul.
Plugged recirculation system will cause performance issues and excessive smoking.

 

[WinnerCougar74]

Awesome. Does it make any difference which surface gap plug is used? Some have the extra spark enhancers built in to theoretically help with this.

 

[Faztbullet]

If carbs,sync and link and recirc system a 2 stroke will troll all day and not foul plugs. Your model has a iffy recirc system due to block design.

 

[tg3690]

" Surface gap plugs trolled for extended times will foul." Have found this to be true with mine.....however a short high rpm run will clear it up immediately. But it will troll just fine for as long as you can stand it. And I use the Champion L20V plugs. Even 4-stoke air-cooled airplane engines will foul plugs if idled for extended periods.....but a full throttle static runup will clear it up just fine.....just like an old Chrysler outboard.

 

[WinnerCougar74]

So far it sounds like Chrysler outboards have a problem with this. So I will keep plenty of plugs in the parts box. Incidentally with the motor titled up the plugs are easy to replace even out on the water. I emailed a mechanic that restores Johnson/Evinrude motors and he claims these motors can troll forever. He says he has engines out there with 5-6 year old plugs. He also claims any CDI ignition is so strong that it won't foul plugs.

This makes me wonder do CDI ignitions get weak or do they either work or fail?

 

[racerone]

So there are more people who say that 2 stroke motors can troll all day long.-----And that plugs do not need to be changed twice a week.

 

[WinnerCougar74]

When saying will foul, you mean the electrode will be darkened, carboned up with use ? If so, this is normal, all 2 strokes motors will go that way compared to 4 stroke plugs. When the plugs are fouled, does the motor hesitates, misses a bit when opening fast the throttle past idle rpm right after trolling for long time periods ?

Happy Boating
​

Yes, after idling for an extended time like 15-30 minutes the engine will start to hesitate. It happened a few times and I throttled it up and it went away but eventually that didn't work. So I replaced the plugs and the motor runs great now.

 

[Scott Danforth]

Yes, after idling for an extended time like 15-30 minutes the engine will start to hesitate. It happened a few times and I throttled it up and it went away but eventually that didn't work. So I replaced the plugs and the motor runs great now.

what brand of oil are you running? the semi-synthetic and the synthetic dont foul plugs like some of the lower quality oils do

 

[dingbat]

Does compression being down by 15-20 psi cause problems with these 2 stroke motors? (a commonly reported thing)

How can it not?

 

[WinnerCougar74]

what brand of oil are you running? the semi-synthetic and the synthetic dont foul plugs like some of the lower quality oils do

Pennzoil Marine XLF synthetic blend @ 50-1 (12.8 ounces for 5 gallons)

 

[WinnerCougar74]

How can it not?

I don't think this video accurately shows how a crossflow outboard works. On a crossflow engine the atomized fuel has to make it's way past the crankshaft. From what I understand the turning crankshaft turns some of the atomized fuel into a liquid that "pools up" in the bottom of the crankcase. This liquid fuel can be a real problem if it isn't moved out of the bottom of the crankcase. I think if the liquid fuel backs up it can get sucked in by the piston and this could easily foul spark plugs. One of the posts said that the design of the fuel recirculation system on Chryslers is a bad design. I think this could be my problem.

 

[WinnerCougar74]

Here is another thought. I simple recommendation is to only fuel up right before going on the water. Fuel that sits around a lot will evaporate then what's left over is not as flamable and also the oil content is to high. This could lead to fouling.

 

[racerone]

Gave the 8 year old grandson a 1963 model 10 HP Johnson.-----Has a conventional magneto.----Coils / points / condensers.------Runs at 24:1 mix.-----Trolls all day long with no hick ups.-----Your post #35 tells me you are not well versed with 2 stroke operation ----A looper style engine works the same way as a crossflow.----Only difference is the intake ports aim the incoming charge so no deflector is needed on piston top.------Sorry to be blunt here.

 

[WinnerCougar74]

No problem racerone. Sometimes this is how myths are eliminated. I'm still trying to fully understand the 2 stroke fuel recirculation system. Why does fuel pool up at the bottom of the crankcase? What causes the fuel to not stay atomized?
Here is something else your comment made me wonder. Do Johnson/Evinrude use surface gap plugs?

 

[racerone]

Surface gap plugs were used in Johnson / Evinrude about 50 years ago.-----On 55 to 125 HP models.------Fuel can pool in an engine when there is not enough HEAT to keep it vaporized !!!!

 

[foodfisher]

Yes, after idling for an extended time like 15-30 minutes the engine will start to hesitate. It happened a few times and I throttled it up and it went away but eventually that didn't work. So I replaced the plugs and the motor runs great now.

They are easily cleaned so you don't have to buy new constantly.