Why my outboard carburetor corrosion?

[vtr1005]

My 4 stroke outboard was sitting about 2-3 months, it couldn't start again last week.
Then I disassemble the carburetor and want to clean it inside.
But badly, lot of corrosion inside the carburetor.

Can anyone tell me why it corrosion like this?
because I store the outboard beside the sea? because the quality of the fuel not good? or any problem?

Any advise can give me ?

 

[Doug Huffman]

Salty water intrusion. The materials making a carburetor are selected for corrosion resistance in 'normal' use. My experience suggests that salty water has been stagnant there for quite a while.

 

[jim hardy]

Did you find a white gel-like substance?
Water made its way into the carburetor.
Even rainwater mixed with gas will eventually corrode that aluminum casting,
Denatured alcohol is a good solvent for it.
And you need to clean out those tiny little passages around idle jet and just behind throttle butterfly - i blow carb cleaner through them

You'll do a lot better to run the gas out of your carb before putting the motor away.
Unplug the fuel line and run it until it won't go anymore even with choke on.

Every Evinrude i ever owned had provision to drain the carburetor bowl-
usually nowadays a flat head screw-in plug on side of carb near bottom.
In the 50's you'd unscrew the high speed mixture knob , if you have one of those see if it goes in near the bottom .

Modern gas in the US can carry water - it is miscible with the ethanol. See if there's an "Ethanol Free" station near you.
If you use those portable tanks - rainwater can get in through the vent on gas cap. Store them under cover.
If it's a tank built into your boat you need to run some gas into a glass jug, let it sit and look for water droplets on bottom. Tilt the boat so any water in the tank will run down to fuel pickup.
Only time i ever got towed in was from rainwater in the tank. My fault, for had i looked carefully i'd have seen it through the translucent plastic tank.

Good luck

old jim