The Seagull Part IV: New Gaskets

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: tracing the lower half of the gearbox.

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.

The Seagull Part II: Taking it Apart

A few months after last year’s final 4-H fair I got to work on restoring the Seagull. I began at the beginning: taking it apart. There was a lot of rust, dirt, and the gearbox behind the propeller was full of an ominous looking sludge. I looked like a drop of seawater had gotten in at some point, it’s a good thing there was oil in there or the corrosive salt water would have rusted the gears.

Above: The gear box after I drained most of the sludge.

After dismantling the gearbox, I removed the flywheel. The flywheel was stuck tight and it took a lot of hammering (and patience!) to get it out. I spend a five hours hammering, tapping, prying and levering on it, and eventually it gave way. Why the hammer? On small motors the flywheel is bolted onto the crankshaft, which is usually tapered. Hammering gently on the flywheel while a helper pulls up will loosen it from the tapered end.

Above: A hammer is a useful for removing flywheels. Don’t get rough!

Above: One end of the crankshaft. Note the taper.

Many of the bolts were stuck and rusted which made it difficult to take them out. When this problem comes up, be very careful. The last thing you want to do is break a bolt. On British Seagulls the bolts are all Whitworth sizes – somewhere in between metric and imperial – but not quite a perfect fit on either of these sizes. Whitworth wrenches aren’t something you can find at your local Canadian Tire store and buying replacement bolts is difficult too; regular hardware stores don’t carry anything that fits. It’s best to go to a specialist.

Now I had an awkward combination of problems: jammed bolts and tools the wrong size. Eventually, by combing through my grandfather’s tool room I found a bit which fit quite well onto the desired bolt. I carefully loosened the bolt by slowly pushing the rachet back and forth. This can break the corrosion holding a bolt in. I levered the ratchet back and forth, gently, loosening all the rust and dirt around the head of the bolt. Whether it takes one minute or one hour, take your time with this process. You don’t want to break anything!

British Seagulls are water cooled: Water from the ocean is drawn in and forced up a pipe by an impeller to the block, where it fills a chamber that encircles the piston. On my Seagull this water chamber was heavily clogged with rust and it was obvious no water was going anywhere. In the photo below the engine head is removed to reveal the four inlets from which you can access the water chamber. This is handy because through these inlets you can see and clean inside the water chamber. The rusty material blocking these inlets is the rust.

Above: The block, note the water chamber inlets. There are four inlets, one on each side.

Above: The inlets to the water chamber – much more visible after sandblasting.

Above: The crankcase. It splits in half, making it easier to take the cams and piston out.

Next, I’ll talk about the fun part: Sandblasting!