[Andy b]

Went to help a friend with his boat today as it was not running well
on inspection of the carb we discovered this.
Any idea what it is? and what's caused it?
there's nothing in the filter or the strainer in the carb. just the float bowl. no sealant has been used in the carb, and I was wondering if ethanol would have anything to do with it.
when dried out it goes to a crystalised state.

[blockp]

That's exactly what I found in the carb bowl and jets of a riding mower I just bought. I'd be curios to know what causes it too... and what cleans it up.

Carb cleaner didn't do much of anything to it. I ended up using a pick to clean out the jets, then sprayed carb cleaner through them to blast the stuff out.

[ColoradoDiablo]

Take a look at this Andy. It explains lots on the cause and effects of ethanol fuel.
It sure sounds and looks to me that you hit the nail on the head with your diagnosis.

[Andy b]

Cheers Larry, interesting reading