1998 Merc 15hp 4 stroke... Sludge in float bowl

Swedefj40

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Every month or so I have to clean out the pilot jet on the carb of my 1998 Merc 15hp 4 stroke outboard because I keep getting this weird jelly like sludge build up in the float bowl. It ends up clogging up the jet and won't idle. I'm using fresh 91 octane marine gas in the portable tank that is ethanol free. The outboard is only used as a trolling motor. What is this stuff and how do I eliminate this from happening anymore???
 

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DeepCMark58A

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Strartron fuel additive, I use it in all boat motors and small engines. Some here will rip it but I have seen the difference it makes.
 

Texasmark

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I have used Startron when WW sold it (long dry spell)....which, by the way I was in one and they had plenty....so I picked up 4 bottles. Back when it first hit the market, I read up on the company and the product and was convinced they had something going...enzymes work elsewhere why not in gas too?????? In the interim I used Sea Foam, available in auto parts stores and WW which does a super job of keeping things clear. I bought 3 cans of that too as I was out.

Water in gas will make for a sludge when a water absorber (from whatever source) attacks it. Back in the days of real gas, I had a built in tank and one day figured my BIT surely has some condensation to control so I dumped some kind of something in the tank to absorb it.

Running at a good clip one day, out in the middle of this huge lake, my Jonny 125, which had never given me a problem, just died. Inspection, at the hose-engine connector location revealed a semi clear, gray Jello. Used the squeeze bulb to pump the mess into a used container (guess what kind...grin) hooked the hose back up, pumped the bulb, lit her off and back to what I was doing.
 

Swedefj40

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You mean like this?
 

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Swedefj40

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I'll have a look but I doubt it since the inline fuel filter right before the carb is not getting clogged up.
 

Texasmark

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I'll have a look but I doubt it since the inline fuel filter right before the carb is not getting clogged up.

On the gray fuel line it doesn't matter. I had tan crud block my line at the fuel inlet to the engine and after changing line and squeeze bulb, engine ran fine and I was still using the same engine mounted fuel filter which was flowing just fine.
 

Swedefj40

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Update... well the issue is basically gone after I was chatting with a co-worker about it. He asked if I ran the outboard dry when I was done for the day and I said yes. He then asked if I'm using Marine fuel in it and I said yes. He then told me that the Marine fuel has a dye in it that will gel over time if exposed to air and to try not running the engine dry for the season and see if it helps. It did. Ran great all year with no issues. I did run it dry when I put it away for the winter and had the sludge again this spring. So I think we have it figured out.
 

Faztbullet

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What is marine fuel???? Marine fuel in my area is diesel and it is dyed red as its for offroad use. Gasoline is gasoline just different octane ratings, but suspect your running a E10 blend. We call what you seeing ethanol salt or slag. Ethanol slag is high alcohol content,moisture and aluminum oxide, This is what pits the bowl.
 
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Swedefj40

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Marine Fuel is a higher octane (91), No ethanol, dyed purple and is taxed a lot less here in British Columbia.
 
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