White powder spot in bilge area

[kriskro]

Hi,

I decided to spend a bit of time to clean the bilge area and keel bolt nuts of my 50 years old boat and notice a white powder doming out of the fiberglass in one particular spot.

I have attached an image.

Any idea of shat this could be ?

[kriskro]

Here is another pic

[Alan Mighty]

Just guesses until you can give more information:

* could it (the dark circle centred on the white) be a hull repair, filling in what was a thru-hull for a water-speed sensor or even a seacock?

* if the hull is out of the water at the moment, could you report back on the outside of the hull? any surface irregularity there? if sounded with a hammer, any irregularity? if you run a moisture meter over the hull, any irregularity?

[kriskro]

It is effectively surrounded by a kind of black greasy texture.

When i repainted the bottom last year, i haven't noticed any irregularities. It looks like a a king of mushroom or crystal that formed...

I may give it a light sand to see if this is only on surface or if this comes from deeper in the fiberglass...

[Rob_P]

Run your fingers through the greasy part and then smell them. Depending on what it smells like, you can hopefully determine what's causing it.

You can also scrape off the crystal growth and put it into a tiny bit of water to see if you can reconstitute it. Once it's wet again you might be able to tell what it is by the odor.

[jim King]

It looks like mold to me. Not uncommon in closed in areas that can contain moisture like a bilge. Have you tried removing it and seeing if the area underneath is soft of has a hole? This could indicate a more serious structural problem.

[Cheechako]

Try to scrape or wire brush it off. Are you sure it is "coming out" of the glass?

[P3sailor]

white powder is usually associated with aluminum corrosion or cocaine, neither of which applies here. Could be salt buildup.

[Enrique100]

This reminds me of efflorescence, which is a salty residue that gets pushed through an object by osmosis. Which would mean moisture/leak, which would be bad news.

[Searles]

Simple test taste it, just a little ,you may quickly identify it ,with an old glass boat could be the remains of old fittings glassed over long ago ,any Idea how thick the hull is as it appears to be close to the turn of the bilge .hasten slowly. ⛵️⚓️

[Clivevon]

It would be easy enough to do a litmus paper test (more info here: https://www.bbc.co.uk/bitesize/guide...q6f/revision/1 ) to see if its acid or alkaline, which could help identify what it is. Scrape some off the hull, place in water, see if it changes the ph of the water.

Otherwise just keep an eye on it & see if it multiplies?

[silkie]

If it dries as fast as the rest of the bilge, I would just clean it up. Investigate if it comes back.
If it seems to stay moist, investigate fully.

[kriskro]

I may try that
- remove and keep the residue to investigate
- cleane and lightly sand to see how the fiberglass is below

If dry, hard and of the right color, do nothing and monitor,
If not, I may investigate further at the next haul out and see if there are any issues on the other side like cracks gelcoat or old repairs that are not watertight anymore..

[PaulvR]

Many feel that 'lightly this' and gently that' is the approach. Not for me!

It is the HULL, the bottom of your boat and the end of your world if it fails!

I'd attack it aggressively with course sandpaper, and then more carefully with a variety of sharp instruments.

If at any stage you feel you need to treat it gently to stop things coming apart, you should haul immediately and investigate fully.

If you see increasing moisture, (as mentioned by others), as you dig around, or if there is any ingress of water whatsoever, stop, haul.

For me it is simple, if I can burrow a hole and cause water ingress through a soft spot below water by using nothing but hand-sanding and/or prodding by hand, I would haul immediately...

A stitch in time saves lives...when it comes to a hull.