Mysterious Black Spots

R

rcwass

New member
My C-Dory was on a boat lift in Maryland for 6 years. I started getting these tiny pin head black spots all over the outside of the boat. These are like raised bubbles and are hard. My boat is a 1990 that has been exposed to California and Maryland sun since new so the gel coat is pretty much gone. When I scrape these spots off they leave a stain in the fiberglass. I've since moved to Maine and have noticed these same spots on my galvanized trailer. The boat was on the trailer in California and in storage in Maryland. I haven't found anything that removes these spots or stains. It was suggested I use accetone but I'm hesitant. Does anyone know what these black spots are and have any idea how to get rid of them? Right now I have about a thousand of these on the fiberglass, stainless steel and trailer.

I have photo's if needed but they don't show up that well.
Thanks for your help.
Dick
 
The most obvious GUESS would be liquid ashphalt kicked up from the tow vehicle tires. It would harden over a short time, and when rubbed off would leave a brownish-black stain. They can usually be rubbed out easily with rubbing compound on the boat. Probably on the trailer as well.
 
Those spots could also be organic residue from trees or insects. Have you tried solvents designed to get rid of that kind of stuff?
Pat
 
I've tried mild rubbing compound, waxes and marine cleaners with no results. I've tried scraping the bubbles off which can be done but the stain below is stubborn. I doubt if its asphalt related because the bubble shell is hard and when scraped in the sun there's no smudge.
Thanks for the input.
Dick
 
Perform a search here for "barkeepers".

Barkeeper's Friend is the gelcoat and stainless secret weapon. I've yet to find any gelcoat stain it would not easily remove, and it takes rust off of stainless like nobody's business. Mix it thick with water so it forms a paste, rub it a bit, and presto...

Your stains may be the first it fails to remove...but I'd be surprised.
 
Patrout":950fj2lg said:
I get my Barkeeper's Friend at Walmart.
Click to expand...

Yup...I've seen it at some Safeways as well. Not sure how wide-spread Smart & Final is, but that's where we get ours - they sell a 3-pack of tall cans cheap.
 
Dick,

Was your boat near any oil wells? An oil well near my marina in LA leaked and sprayed a fine mist of crude oil into the air. All the boats in the marina had tiny black dots!

Paint thinner or kerosene would dissolve asphalt, tar, or crude oil.

Acetone or lacquer thinner will also work and since it won't hurt galvanized (or stainless) steel I would practice removing the spots on the trailer or SS rails first!
 
Dick,
Scrape off a bit of the black and take a taste....I bet you can figure out what it is without having to call 911. If it taste nasty spit it out and rinse with Jack Daniels. Heck, I might have to look for some black spots on my boat now I think about it.

Mike
 
I do not want to be an alarmist, but when you said "bubbles", it may be what is referred to as "osmosis". I am no where near an expert, but if you go to the bottom paint discussion refer to the aurora web site, www.auroramarine.com. Join the aurora marine "club" and search for osmosis. They have a picture posted of the bubbles. THEY ARE NOT BLACK, SO THIS MAY BE A FALSE ALARM. But it's worth the effort to eliminate this possibility.

John
Swee Pea
 
Mike I think you are right on this....but I'd keep the Jack handy just in case. Ya never know when it might start hitting the metal stuff...
 
Osmosis, or blistering, is pretty easy to see and identify. Even the untrained eye will recognize it if they see it. Just go to any boatyard and look for boats with lots of spots sanded or opened on their bottoms. Then go to a boat on blocks with a dry bottom but no prep work and spot the blisters. This can and does happen in all regions, types of weather, salt or fresh water. They vary in size from the size of the lead in a pencil to a silver dollar, and are usually round. Once they get past a dime or so the chances of them going into the core material is much greater. I haven't heard of C-Dory having much of a problem, but I am sure there are a few around in this brand as well. But the problem in this thread is not osmosis. They don't take on a color, at least not much. If you drain a blister the liquid will come out about the color of light varnish, and will smell somewhat like varnish, because it has some of the same chemical makeup. But these black spots are kind of intriguing. If it isn't petroleum, it almost has to be some foreign substance landing on the hull, then possibly reacting with sunlight. Maybe some petroleum based substance or insecticide emulsified in the water the boat is in.
 
Two possible explanations arise:

1. Bug poop. (or)

2. For years cosmologists have speculated about where all the material goes that is sucked into giant black holes in the Universe so large that not even light can escape their gravitational pull. Where can all those untold billions of suns masses of matter be? Is it all locked up inside the black holes? Or does it reappear in another parallel Universe at another time or dimension of space? Could it reappear as black spots on boat hulls in Maine? Inquiring astrophysists want to know!

Get the BarKeepr's Friends:

Booze

Friendly Women

Scouring cleanser
 
rcwass – I get the same thing on my boat. If I clean it on a regular basis the spots come off easily. My boat is stored in my equipment shed and I believe the spots are caused by spider poop. The spiders are in the rafters above my boat, the spiders catch other insects, suck their juices out, then poop on my boat. I put up with it because they keep the insect population down.
 
rcwass I too get the black spots, mostly on and around the lazarette hatches. Since my boat is moored below the end of the San Diego airport runway, I hope it isn't another version of oldgrowth's "spider poop." I thought it was JP5 soot but now Dave's got me wondering....


Don
 
Don,

Keeping a boat near an airport will give your boat 'grey spots'!

I have had this problem in Newport Beach, CA and Camarillo, CA, both under airport flight patterns.

I think it is unburned jet fuel. The spots start off small and grow and turn grey or black. I think its fuel residue that then catches dirt or soot(smog?).

Spider poop is a good possibility also. I have a shipping container on a farm that gets small dark brown spots, They are flat and in clusters. There are lots of spiders there.
 
Thanks for all the input. I'm still troubled by these blac spots. The spots are all on one side, from the roof to the waterline. On the aluminum window frames, Stainless Steel railings, Galvanized trailer and the fiberglass. The spots are continueing because they're on my new registration numbers and State Decal. I've tried accetone, paint thinner, mild rubbing compound, bottom cleaner, fiberglass cleaners, three different brands of goop off or goo off, and bleach. I scrape the hard bubble shells off then apply the cleaners to the stains as on the directions. Scrub, scrub and scrub more with no luck. I've taken pictures to Marine Shops with no help. The cleaner that works the best is a small can of Goop Off but even that leaves some stain. I can clean the spots off the metals with accetone but the metals aren't porous. I.m completely stumped.

I appreciate your help.
Dick
 
Collect some in a sterile container and take them to a lab. That would answer the question of what they are and how to deal with them. You have us all wondering now.
 
Lorraine J:

Without a doubt you being plagued with spider or other insect such as love bug droppings. This is a common problem if you live or keep your boat on the water. First get rid of the spiders by spraying an insecticide, if possible. Do a web-search "Cleaning spider droppings" and you will find several recommended products and techniques for cleaning your boat. Keep your boat waxed and if necessary lightly cover it with a disposable drop cloth. I am confident that your black spots will disappear. I have found that spraying the fiberglass or aluminum with a spray protectant such as 303 after the spots are removed helps. It does make you boat slippery, however.

Best regards,
Rollie/C-Batical
 
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