While there are many manufacturers of paste form-a-gasket materials, Permatex is among the most well-known. The company founder made his first form-a-gasket material, used to prevent blowouts on the head gaskets of early race cars, in 1915. Permatex makes a wide range of gasket products, and while the “liquids cart” in my shop includes a dozen examples, I’ve used the following products to meet most of my machinery-sealing needs ashore and afloat.
High-Temp Red: This paste, rated to 650 degrees Fahrenheit, will dry in one hour and is fully cured in 24 hours. I've used this for general sealing applications for 40 years. It resists coolant, water, automatic transmission fluid and oil, and comes in a squeeze tube. It can be used to make or replace a pre-cut gasket. Permatex Ultra Blue is very similar to Red, but is rated to 500 degrees Fahrenheit.
Ultra Copper: This bronze paste is rated to 700 degrees Fahrenheit. It will dry in one hour and is fully cured in 24 hours. Well suited for high-temperature applications, such as exhaust manifolds and turbocharger flanges, it too comes in a squeeze tube and can be used to make or replace a pre-cut gasket.
After applying a bead of either product, the parts should be immediately assembled finger tight, allowed to sit for one hour then fully torqued. Don’t apply too much sealant, because it tends to squeeze out into the assembly; a 1⁄16-inch to ¼-inch bead is sufficient. Be sure to surround all bolt holes. Don’t expect paste gasket material to fill large gaps or irregularities (certainly nothing more than 1⁄16 inch, and less if under pressure).
It's worth noting that, other than in threaded applications, few if any paste gasket-makers are rated for continuous immersion in fuel. For instance, fuel tank sender gaskets should seal without the need to be augmented with sealant. Highside Chemicals' Leak Lock — a blue paste dispensed from a brush-in-lid bottle or squeeze tube, is a thread sealant that is designed for use with fuel as well as many other onboard liquids, including potable water. It's a must-have for your gasket kit.
High Tack is a purple liquid (with brush-in-can lid) that's rated up to 500 degrees Fahrenheit. Cure time is almost immediate, but surfaces can be coated in advance and allowed to dry to a tacky film. It's effective on threads as well. This product is designed to be used with gaskets, as a dressing, rather than in place of them. I've used High Tack to adhere gaskets to surfaces where they may otherwise fall off or out of place during assembly. I learned the hard way that it's called High Tack for a reason: It is a tenacious adhesive, so use it sparingly if you ever intend to disassemble the part.
In addition to the above gasket-makers, there will be times where you'll want to duplicate an existing gasket that has failed. Rather than using the cover of HO249 or a chart, it's best to stock a generic gasket material kit. These are available online and in auto-parts stores; they include a selection of gasket materials, including rubber, paper and cork (but don't use cork with fuel applications).
To make and install gaskets, the necessary tools include a heavy-duty set of scissors and a gasket-cutter kit. The latter includes a series of round punches that allow you to cut circles in almost any gasket material. Failing to completely clean away the remnants of the previous gasket often leads to leaks. This can be accomplished using a proprietary gasket scraper, which is available in two types, with and without a replicable blade. I prefer the latter because they can be sharpened over and over again using a file. They are also less delicate, and you can lean into them on stubborn gaskets without fear of breaking them. These are available in several widths.
Final surface preparation often benefits from scouring with a 3M Scotch-Brite pad followed by cleaning with a solvent such as brake cleaner, mineral spirits or 3M general purpose adhesive remover.
Steve D'Antonio offers services for boat owners and buyers through Steve D'Antonio Marine Consulting.
