Fuel Filter basics - for outboard engines

[kmacdonald]

Whats the fuel tank made out of? That looks like rust.

[Marqus]

Originally Posted by kmacdonald

Whats the fuel tank made out of? That looks like rust.

Red plastic tank.

[Marqus]

Originally Posted by thinwater

You did not say if there was ethanol in the gas. It matters.

There are two things that make it go yellow.
[LIST=1][*]Air exposure. Close the vent.[*]Exposure to copper and zinc ions related to corrosion.

Thinwater, it's zero ethanol unleaded gasoline (was mentioned somewhere).

All plastic tank. The only metal involved before the outboard would be the alloy parts of the filter housing. So I thought, the fuel inside the filter may look different to that in the plastic tank due to exposure to the alloy - but no, the same color.

Here's a photo showing fresh gasoline (right side) and gasoline from the plastic tank (left). Does the fact that it has a deeper yellow color have any implication for how it might burn in an outboard?

[kmacdonald]

Get rid of the old gas and get new gas. Clean the tank while you're at it. How old is the gas? Does it smell like varnish?

[Marqus]

Just to clarify, with the gasoline color issue, I'm not trying to save the old gas. Instead, I'm just trying to learn something for future use.

Whether it was stored for a week or a month or four months, if it turns yellow like this - why does it happen and what if the outboard burns it?

Maybe it takes a chemical engineer to answer that, but I've been surprised in the past how scientifically literate and seriously smart some of this forum's readers and posters can be.

[thinwater]

Originally Posted by Marqus

Just to clarify, with the gasoline color issue, I'm not trying to save the old gas. Instead, I'm just trying to learn something for future use.

Whether it was stored for a week or a month or four months, if it turns yellow like this - why does it happen and what if the outboard burns it?

Maybe it takes a chemical engineer to answer that, but I've been surprised in the past how scientifically literate and seriously smart some of this forum's readers and posters can be.

(Chemical engineer)

Two reasons for the color change. One is oxidation from air and metal ions it may have collected up-stream. The second is that gasoline varies considerably in it's storage stability, and some will begin to polymerize and yellow spontaneously. They should be inhibited, but....

Will it affect the engine? Very difficult to say. Often it is purely cosmetic but sometimes it can increase gum formation and jet clogging over time.

If the vent has been closed and it has only been a few months, it is likely just cosmetic. But I would start closing the vent and using an additive (not just any additive--many do nothing and some can actually make it worse).

[Marqus]

It doesn't get better than this - you ask for no-bull scientific explanation of fuel condition change, and no less than a chemical engineer answers.

THANKS Thinwater, appreciated.