Green Slime/Mold on Carb jets

[Chuck Losness]

Hi everyone. Looking for help with a problem that I have never ran across before. I have a Nissan NS8b 8hp 2 stoke outboard that I use daily on my dinghy. Starting last November a green slime/mold started to form on only and I mean only on the two brass jets in the carburator. The rest of the carb and all of the little passage ways stays bright and clean. The gas was new and I use a fair amount of gas. About a gallon to 1 1/2 gallons per week. It takes 3 to 4 weeks for the green slime/mold to form and plug the jets. Clean it all up and 3 to 4 weeks later it's back. I have replaced the inline filter and that made no difference. The gas has been purchased in different ports in Mexico. I use penzoil 50:1 oil and have used oil from two different lots. One purchased over a year ago and one purchased recently. No difference.
Anybody have any idea what is causing the slime and how to get rid of it.
Thanks for your help.
Chuck
S/V Hale Moana
cruising in Mexico where life is good and the living is easy.

[kenJ]

green on brass might be caused by salt. Is there alot of salty humidity in the areas you have been cruising since it started? Could you have a small leak in the cooling system that is atomizing cooling water that is being sucked into the carb? Can the jets be seen without dissassembly? If yes, a weekly shot of carb cleaner may help lessen the problem.

[Chuck Losness]

I have been down here for several years. And the jets are inside the float bowl and my guess is that they are always in gasoline. So no way for salt spray to even get close to the jets.

[Frosty]

Im clutching at straws here but IMHO I would--- use only marine 2 stroke oil.

I would make sure all earth straps are on the engine and have not corroded.

Little Nissan 8 you say? I got one of those, great little motors.

Is the tank clean? Apart from that I dont know ille think about it

[kenJ]

Some less knowledgeable folks call the air intakes and ports in the carb throat "jets" so I had to ask. Are you using ethanol or straight gas for your mix? Ethanol loves to absorb water, let it sit in a carb bowl over the winter and it will really make a mess. It sounds like you are running the engine enough so it is not a sitting around problem. How about the fuel source. Are you filling a jerry can then transferring to a little jug as you mix? 3-4 weeks should be the last mix out of the jerry can before refill, it's been heating and cooling, condensing/absorbing water. A good fuel stabilizer such as Sta-Bil really helps reduce the bad habits of ethanol and will help keep real gas free of water. I've got the NS5 hp little brother, it is also a great engine.

[marshmat]

Maybe the Japanese motors are a bit more sensitive.... but we regularly burn year-plus-old TCW3 mixed gas in a 1979 Johnson 9.9 and a 1994 Johnson 30, never had a problem with fuel on either. The J30's tank gets stabilizer for the winter, the 9.9's tank just sits out in a cold shed for ten months and the little thing starts right up come springtime. So I don't buy the "old fuel" argument, at least not with Canadian summer gas (up to 10% ethanol) and old carb 2-strokes. (No offence, Ken.)

Chuck, are you noticing any erosion on the brass surfaces after you clean them? Are they pitting at all, or wearing down? Or can you still see the original finish from the lathe they were cut on?

[Chuck Losness]

I doubt that the gas I am buying in Mexico is ethenal. And old gas is not a problem. I go through 6 gallons every 4 to 6 weeks and the outboard is run every day. I am not the orignal owner of the outboard, so I don't know what a new jet would look like. But I am not noticing any pitting or erosion of the brass surface. The most baffling thing is that it only forms on the brass and everything else is bright and shiny clean. Maybe I am getting a little water from somewhere that would cause to the brass to turn green but there does not appear to be any water in the gas tank. I pumped some of the gas into a cup and no water separated to the bottom of the cup. I have to haul the boat for the summer (hurricane season) next week because I need to go back to California earlier than normal to help my kids with some things. So the outboard will be flushed and cleaned next monday and put away till October. I'd like to thank everyone for their input. Maybe the problem will disappear next year. Who knows.
Thanks
Chuck
S/V Hale Moana

[Typhoon]

We had a problem a few years ago here with improper treatment of fuel at the refinery causing an algae growth in fuel systems, it grounded our piston engined aircraft fleet.
Probably a similar thing over tehre I would say.

Regards, Andrew.

[Chuck Losness]

I think that I have discovered the cause of the green mold. Poor quality regular gas in Mexico. Two months ago I switched to premium gas and started using an octane booster. Have not had any green mold since then.

[CDK]

The fuel contains sulfur as an organic compound called thiol or mercaptan. The small voltage potential between the brass jets and the surrounding aluminum, combined with traces of moisture is enough to start a chemical reaction and produce greenish or blueish organic copper salts.