Some years ago we were introduced to RTV silicone gasket material by a Maine diesel mechanic. He used this to fix a small leak on Beowulf’s Yanmar diesel, and told us that he rarely used paper gaskets anymore.
We’ve since carried an inventory of this material. It is good for replacing gaskets, and if there is a mating surface that is somewhat unfair, where a paper gasket is not doing the job, the RTV is a miracle material.
There are various types of this material available with different temperature ranges. This photo is of a tube we’ve been using on Wind Horse, to deal with a couple of fittings which have had tiny oil leaks.
Use of the material is pretty straightforward. Clean the surface as well as possible, apply a generous bead, and reassemble. Take care not to create so large a bead of material that it can break off inside the engine cavity or block any nearby orifices.
As this material cures on contact with moisture in the air, you need a good sealing system for the opened tube. For many years we’ve used a small piece of Saran Wrap over the threaded opening as a seal. Once the cap is screwed over the Saran Wrap, the air is sealed out. The tube in the photo has been open for six months and it is still usable (the same system works with all silicone and other air curing products).