Obtaining new gaskets to replace old ones, whether it’s buying a brand new set or making your own, is an important part of restoring a motor. Gaskets seal the space between the components of an engine – increasing the amount of compression necessary for an engine to perform well. Poor gasket = poor compression. The types of gaskets vary: some are thick while some are made with thin metal. It is very important to know which type of gaskets to use on your motor. On the Seagull all gaskets were the same thickness, except for a fat copper gasket which fit between the head and the block. I never replaced this one because it was in good condition. Gaskets generally decay because the heat from the block will ‘melt’ the gasket, causing it to fuse and bond to the block. When you’re removing them you’ll notice that they will often need to be ‘peeled’ off their seating.
I had some leftover gasket material from an outboard I restored a couple of years ago which would work. You can get this sort of material at most automotive shop. Fortunately it was very similar to the Seagull’s original gaskets.
I started by tracing the shape of the object onto the gasket material. There is no right or wrong side with this material (be careful though – this might not be the case with all gasket material). Use a pencil so you can erase it if you make a mistake. I included screw holes that were on the original gasket.
Above: This tracing job isn’t very good – what line should I follow? I decided to redo and make it more accurate.
After tracing, I cut out the gaskets using a very sharp knife. The gasket material is like cardboard and just as hard to cut. The first time I made gaskets I was a bit hasty and my knife got stuck, then it would slide out of control if I pushed too hard. A definite learning curve and I wasted a lot of material. This time round I took more time and got a better result:
Above: Punching holes for the screws (using a plain old hole punch). I left a space around the trace to account for the lip in the gear box cover (the gray circular object at the top of the photo)
This way it would fit around the lip and not be too small.