my face John F. Hughes - Personal - Boats
John's Guide to Goo


CLASS I: Engine goo.

Ia: Permatex #2.

Black, consistency of slightly warm toothpaste. Used as a sealant between the two sides of the engine case, between things that bolt to the block and the block itself, etc. Easy to spread on with a finger (preferably wearing a glove), used in fairly thin layers. Usable in warm spots in the engine but not, I think, in the hot ones. For example, on the exhaust manifold-to-riser gasket (aluminum sandwiched around asbestos), I was told to use no goo. Cleanup: stove alcohol, rubbing alcohol.

Ib: Permatex #6, also called "Blue RTV Silcone Gasket Maker".

Like jellied blue gel toothpaste. Used in many places where paper gaskets previously went. Cures on exposure to air, especially damp air. Application is typically done by putting the goo on, attaching the piece to be attached, and then tightening the bolts that hold it in place somewhat, but *not* snug, leaving perhaps a 2/1000" - 5/1000" layer of goo, which then firms up. Next day, you tighen it up to the specified torques. Cleanup: alcohol seems to work OK. I don't recall other solvents. Remarks: Does not handle direct exposure to gasoline.

Ic: Liquid version of permatex.

Essentially a thinned out version of Permatex #2, dissolved in some sort of alcohol. Used for making very thin seals, which is nice in places where lubricating oil will flow, since this prevents the lumps of goop that you often get when you use permatex #2, which can break off and flow through oil galleries and clog things. Often used on aircraft, as I understand it. Cleanup: Alcohol.

Id: Not really a goo, per se, but relevant: LocTite thread cement.

Comes in several flavors, from "please hold this nut onto this stud" all the way up to "make the stud shear before you let this nut come off, damnit!" Loctite is essential on diesels, which have a lovely way of shaking things loose. Use one of the low grades...honest. I usually use a drop of blue Loctite (242?) on almost anything I touch. Also used, in combination with silicone sealant, to make your Norseman terminal fittings on rigging be waterproof. (Note: a reader tells me that "Rigging Only" recommends using plumber's putty rather than silicone seal, because the silicone seal has some acidity that can attack the wires. Sounds like a good plan to me...) Cleanup: Never seems to be a big problem--it comes out with the consistency of milk or cream, usually in droplets from a tiny spout, so you don't end up spreading it around much.

Ie: Nevr-Seez (or something like that)

This is graphite embedded in some sort of oily stuff, and if you put something together using it, you will always be able to undo it. Sort of an oppostite to LocTite. Good places for this are on things like your propeller shaft couplings, which are held in place by lockscrews, etc, but you have to do a press fit to get the thing on in the first place. Put the goo on the shaft before you press it together, and you may have a hope, some day, of getting it off again. Cleanup: I know of no god cleanup, but I caution you that the stuff spreads like wildfire, so apply it neatly and carefully, and wipe everything with paper towels when you're done, so you don't track it all over your boat. Note: This also comes in a spray can, which you should never let aboard your boat.

These next two items are from Rob Scott

If: Permatex #83H, Super "300" Form-A-Gasket

A very thick and gooey sealant, but good for somewhat uneven surfaces or where seal is exposed to synthetic and high-detergent oils. Quoted from the blurb on the can: "For difficult assembly problems where seal is exposed to synthetic and diester-type oils and lubricant: Automatic transmission fluids - high detergent motor oils - gear lubricants - diesel fuels - aircraft lubricants - high compression milled heads - seals - cover plates - housings ..." This stuff goes on as a thick paste, and it should be applied on VERY clean surfaces (cleaning with high-volitility brake cleaner recommended). Surfaces may be assembled immediately.

Ig: Permatex #3H, Aviation Form-A-Gasket

A moderately thin sealant, but forms a SIGNIFICANT seal. During my college years when I drove VW bugs and camper vans of less than new vintage, I found that this stuff would certifiably make Volkswagen air-cooled engines cease leaking oil. This stuff should go on clean surfaces, and should be allowed to air dry to a tacky surface before assembling (typically a few minutes). From the label: "For use on most types of gaskets, machined surfaces and screw thread connections of airplane and automobile engines. - Applied as a liquid - changes to a paste in a few seconds - Pressure resistant and leak proof to high octane gasoline, grease and lubricating oils (up to 400F) - Resists hot and cold water, anti-freeze, glycerine, fuel oil, kerosene, butane and other fluids"

CLASS II: Deck goo.

IIa: Silicone seal.

Used for sealing rubber gaskets in portlight housings, and often used on mast boots as well. Silicone (especially Permatex Clear RTV) is a great thing to put on the ends of cotter pins and other sharp protrusions to keep them from snagging sails, etc. Because it can be peeled off fairly easily at the end of the season, it's a good compromise between effectiveness and removability. Application: straight from the tube, in a nice even bead. Preparation: clean the area to be sealed with acteone (if metal) or alcohol (if rubber). Cleanup: I've never found anything that really takes this stuff off. Greg Mansfield gives the following suggestion: after you make your bead of silicone caulk, coat your finger with dishwashing liquid. You can now shape the bead without the silicone sticking to your finger. Wash your finger when done. The silicone cures on the fitting eventually, and then you can wash away the dried detergent. One netter suggests scraping off silicone as much as possible, and then attacking it with Boat Scrub, a cleaner/liquid rubbing compound that is a low-grade acid as well. Worth a try... Remark: Gerald Belton tells me that none of the silicone-based products work if they are exposed to raw gasoline.

IIb: 3M 5200, other polyurethanes

Application: it comes in both toothpaste-tube and caulking-gun sizes. For either, it's best to have a "clean" assistant, who stands by with paper towels, rubbing alcohol, and clean hands. Typically you can lay on a nice bead from the tube or the caulking gun. Seal the tube immediately! For the caulking gun, I like to put a long nail or screw into the tip, so that I can heave it out the next time with a pair of vicegrips. This stuff sets up on contact with water, and sets hard and tenacious. The caulking tube will harden (in its entirety) after about 2 days, even if sealed up, once you've punctured the tip and removed the protective "pop top" on the other end. Cleanup: Stove alcohol or rubbing alcohol take this stuff off like you wouldn't believe, as long as you catch it while it's wet. Nothing will help when it's dry. Acetone *doesn't* work well when it's wet, oddly. Remarks: Put this stuff on a fitting only if you know that you will never, ever, ever want to take it off again. Don't believe me? Ok, take a sheet of plywood at home, and put an old fitting onto it with 5200. Wait a week. Now remove it (or try to). My guess is that you will split the plies in the wood before the fitting comes loose. It's amazing. So, in short, it's both a sealant and a powerful adhesive. Larry Swift advises that when 5200 is left open, it tends to harden in the tube, but that he has kept it in a ziploc bag for over 2 months after opening, and it didn't harden/set up.

IIc: 3M 101, other polysulfides

Application: Once again, it's nice to have a clean friend helping. The solvent in this case is mineral spirits rather than alcohol. 3M 101 smells (from the sulphur, I guess) like a particularly malodorous barnyard. Fortunately, it cures with exposure to water, and the smell dies down after a day or so. It remains quite flexible (and even gooey) internally, long after it's applied. Cleanup: Mineral spirits. Remarks: If you want to bed teak with this stuff, you need to do a little thinking. 3M makes a product that you paint the teak with (looks a little like varnish) to make the 3M101 stick to it properly. This stuff costs plenty, and only comes in quarts, I believe. People like BoatLife also make polysulfide sealants, and also mark the teak-preparing agents. I don't know about smaller quantities. COMMENTS: According to someone on the net, 3M101 is the only one of the products mentioned that is suitable for caulking teak decks, as the others are attacked by sunlight. Of all the polysulfides, he believes (based on experience) that the best one for caulking a teak deck is made by Detco. All of them require a primer for use on teak. Also note that the whole Sikaflex line of products (only one or two of which may be available at your typical store) vary according to adhesion and flexibility; one netter recommends Sika 231 for bedding stuff that may need removal, rather than the 240 or 241, which he found to be far too adhesive (like 3M5200).

CLASS III: Plumbing goo.

IIIa: Pipe joint compound

This is yellowish stuff that plumbers used to apply to the ends of pipes before fitting them together, It helps seal the threads on the pipes. Now almost universally replaced by teflon tape.

IIIb: teflon tape

This non-sticky tape gets wrapped around the threads of a pipe (about 2-3 layers thick) before you screw it into a fitting. It deforms and fills any gaps in the threads. If you have to clean old teflon out of threads before reassembling a fitting, your best tool is a brass wire brush, available in the plumbing section at Sears, etc. Don't get steel---it'll just rust aboard, and will try to scratch the brass pipe you're working with. Note that the pipe threads *will* cut through the teflon tape, making a good electrical connection, so it's perfectly OK to use this stuff on the zinc for your heat exchanger. Don't believe it? Get out your ohm-meter and test the resistance between the zinc and the case of the heat exchanger.


There is now a liquid "teflon tape" product, which is nice for using on large threads, or wherever it's tough to apply the tape.

IIIc: PVC pipe glue

Toluene-based (?) stuff that you apply to straight (unthreaded) PVC pipe and to unthreaded fittings; you wait a few moments and then shove them together. The toluene evaporates into the PVC or something, the semi-liquid PVC repolymerizes, and everything is mated together perfectly, forever. Cleanup: I know of nothing that will clean this stuff off. On the other hand, there's no excuse for getting it on your skin, since solvents like toluene get right through your skin and head for your liver like homing pigeons (or so I was once told by an MD). If you make a point of keeping a bit of cardboard under your work area, you should never get it on the deck, either.


IVa: Vinyl glue.

This stuff is used to repair vinyl cushions, the dashboard on your car, and the particular mastboot that I happen to use. Nothing special about it.

IVb: Polyester Resin

Used for gluing up layers of fiberglass, and other applications. The MEK peroxide that's used as a catalyst for this stuff is extremely aggressive as a solvent and also very toxic. Don't mess around with it. When the resin has the catalyst added, it starts to cure (harden). When it gets to feeling like snot, it has "banged", and will no longer work as a decent adhesive, so you should stop. Always wear gloves. Cleanup: Acetone works best, but don't breath the stuff--it's very bad for you. Advice: Get a good book on working with fiberglass and resin before you start using this stuff. The FAQ for has some suggestions.

IVc: Epoxy Resin

A two-part compound used for gluing up layers of fiberglass, wood, and even some metals or plastics. The working time is longer than that of polyester resin in most cases, and (for WEST system epoxy, which I love) the cleanup is simpler. There are many varieties, varying in mixing ratios (from 1-to-1 up to 5-to-1) and mechanical characteristics, but my experience is that all can be cleaned up with rubbing alcohol. Cleanup: Rubbing alcohol. Suggestions: Get a good book before starting. The Gougeon Brothers on Boatbuilding is a good one. Also, if you're using West System resins, learn (early!) how to use their fillers and thickeners. It makes a job a lot easier.

IVd: POR 15

(Courtesy of A paint type material, good for stopping rust, epoxy type paint cures on exposure to moisture. This stuff will not lift at the edge like regular paint due to the way it bonds with the metal. POR is resistant to abrasion and chemicals including acid. Good for battery trays, tools, anything metal that wants to react with salt. Used it to recondition all coolant hose fittings on a 3116 Cat that were rusted and leaking. Used exensively for auto restoratons. Cure time, less than one hour with about 20% humidity minimum, great underwater, and has wonderful adhesive propetries, comes in silver clear and black Cleanup: When wet, laquer thinner; When dry, nothing Suggestions: Gloves and disposable applicators brushes etc. if you get some on your skin, it takes about a week to come off, 5 days with intense scrubbing. Drawbacks: photochemically reactive, sun exposure (constant) dulls finish and turns the silver color to green

IVe: Marine Tex

(Courtesy of Steve Weingart:) It's really a filled, two part epoxy, and has a million uses for gluing and filling. You mix a paste and liquid hardener to get a sticky toothpaste-like goo. It can be used in emergencies to patch small holes in a hull (even underwater) or an engine block. If you are willing to live with *complete* permanence, it will glue a bolt into a stripped thread. What it's really great for is filling cracks and dings in fiberglass, wood or metal. Cleanup: unknown. When dry: nothing.

More miscellany

Finally, some notes from Dave Kinzer that I found so interesting that I've simply included them in their entirety:


Loctite threadlockers are half-empty when you buy them because the free oxygen in the bottle prevents them from hardening. The bottles are made of something that is semi-permiable to oxygen. This means you should not combine two bottles to make a full one, nor should you put them into some other type of container. The products also cure when you combine them with an active metal like zinc or brass. You should avoid touching the dispenser to the metal you are applying the product to. Loctite does not cure well on inactive metals like aluminum and stainless steel. For these situations, Loctite makes a catalyst that is applied to the metal first. Primer compound 'N' works well and is available as a spray, making this an easy task. Once cured, the threadlockers seal out moisture and salt. This means that you can take apart things later that would have corroded together had you not used it. I do not know if this works for submerged fittings. Like most adheasives, heat causes them to break down. This is useful to remember if you foolishly applied the impossible to remove type of threadlocker to that item you never expected you would have to take apart. Break out that propane torch.


Loctite make a product called 'PST' which combines teflon with their threadlocker product. This is used with tapered plumbing fittings instead of teflon tape. Like the teflon tape, the teflon in this allows you to tighten the fittings to a no-leak fit. The threadlocker in this then fills any voids in the threads. You will not have a leak if you use this stuff (unlike my experiences with teflon tape.) The threadlocker does its regular thing, preventing vibration loosening. Although it seals immediately, it takes 24 hours to fully cure. It is not suitable for drinking water systems. It is messier than teflon tape to apply.


With the West System epoxies, you must make up a minimum batch size since that's what their dispensers dish out. I have had good luck when using small quantities with slow hardener by covering the unused epoxy and putting it in my freezer. This allows me to thaw the epoxy (still covered since this is when condensation will get to it) up to three days later (haven't tried a longer time.) I warm the epoxy with my hand or a hair dryer and use it immediately. I have repeated the cycle with the same epoxy, but by the second or third time out it is starting to set up.