Fiberglass hull cleaning?

[Sunrise Point]

We are about to become the proud owners of a 16 ft., early 1980's sailboat. It has been sitting outside uncovered for the past 20 years and the cockpit and top surfaces (white fiberglass) look awful; probably from a combination of mildew, sap and general grime. The bottom of the boat, where it meets the trailer, is still white and shiny.

If anyone has any cleaning tips, would you please share them? I was going to start with TSP and water, but if there something better out there I would be happy to try it.

Thank you!

[Rattlesnake Guy]

We have had very good success with a product available at the Marinas called Slimey Grimey. The trick is to be patient after you apply. Don't start working too soon. Let it sit set on the hull for a good 10 minutes. A soft brush will make short work of the dirt. Then rinse the dirty results off before the waxing.

[NoBozo]

I use 3M Cleaner & Wax..for "Lightly Oxidized Surfaces"..(09009) which is the least aggressive of the 3M line of three. West Marine carries it. You need to decide which "Level" of 3M stuff you need. I use a slow turning orbital buffer to apply it to larger surfaces. Remove it with a terrycloth (Bath) towel by hand in any case. I have done this on a 32 footer by hand with good results. It comes off easy.

You can also apply it by hand which I also do around cleats, fittings and "difficult" surfaces. I have a 1986 20' Donzi runabout with a smooth foredeck..Vs. a Bow Rider.

You can apply this 3M stuff by hand... or by machine with equally good results. :) NB

[CateP]

Marykate On & Off - Hull & Bottom Cleaner.
Incredible stuff, works great.

[dpg]

Marykate On & Off - Hull & Bottom Cleaner.
Incredible stuff, works great.

On/Off does clean incredible but is nasty strong, wear gloves it burns your skin. Has an acid burning effect if you touch it very long.

[Belmont Resident]

I'd use 20% bleach and water mixture. This will take care of the mold and mildew problem. This will work well on most surfaces including vinyl and outdoor carpet but not cloth. Make sure to wet down carpet first before applying any cleaner to it no matter what type it is.
Do not be surprised if you are left with stains as mildew if left unchecked for time will stain the surface it is on.
TSP is a cleaner degreaser and I’ve found it to have little effect on mold & mildew.

A pressure washer will also help and can be used on just about all surfaces including vinyl and outdoor carpet if used properly. Apply the bleach and let it sit for 10-15 minutes for it to do its work then scrub or wash off.
You may have to repeat the process to get it all or even use a higher bleach percentage.
Do not use straight bleach as it could do damage, I will use straight on wood and concrete but not vinyl or carpets.
Most of the above mentioned products are meant for your hull which I believe you mentioned was clean. Good luck

[JDeere]

Just go to hardware store and buy wood brightener (oxaclic acid). You will find that most of the marine products that claim to clean contain the acid.

Use a sprayer to mix with water. Let it soak for 5 minutes or so and then rinse off.

[COWISLANDDONZI]

Marykate On & Off - Hull & Bottom Cleaner.


It is the best..

[Blue Thunder]

On/Off does clean incredible but is nasty strong, wear gloves it burns your skin. Has an acid burning effect if you touch it very long.

I agree. Awesome stuff but treat it with respect.

BT

[CateP]

I agree. Awesome stuff but treat it with respect.

BT

When I use On/Off I dispose of the sponge because it disintegrates after use. Wear gloves and toss those out too.

[NoBozo]

The original posters question happens to be one of the questions on the Boating Safety (proctored) exam.

Sadly, no one offered the Correct answer. The Correct answer is Hydrogen Peroxide...YUP... AND.. it's safe for the environment..Totally. :D :D

Nope, I didn't make this up..and nope, I've never used it. :look: NB

[Sunrise Point]

Thank you for your responses. We stopped by West Marine in Dedham, and couldn't find Slimey Grimey or M.K.on-off. I was amazed that most of their cleaning products did not list ingredients. We spoke to someone there who pointed out that some of the products would clean fiberglass, but destroy the metal on the trailer.

We will stop by Winnisquam Marine before we go home today, to see if they carry S G