Rust in Marine Engine Water Jackets

By Staff
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The restored engine.
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Figure 1: Palmer L-1 engine before repair.
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Figure 2: Condition of cylinder.
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Figure 5: Broken pieces cemented in place.
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Figure 3: Arc-welded cylinder.
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Figure 4: Weld sealed with epoxy putty.
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Cylinder with fiberglass reinforcement and primer paint.

7964 Oakwood Park Ct. St. Michaels, Maryland 21663

Most modern marine engines have fresh water cooling. That means
that fresh water or a solution of fresh water and glycol is
circulated through the cooling jacket and it, in turn, is cooled by
sea water by means of a heat exchanger and a sea water pump.

Old marine engines that interest collectors were directly cooled
by sea water, leading to rusting of the inside of the cooling
jackets if cooled by salt water. Collectors who have engines from
fresh water areas such as the Great Lakes are most fortunate.

First, a word about the two kinds of rust. Red rust, which we
see on exposed iron and steel, is ferric oxide which is formed when
there is plenty of oxygen present. Black rust is ferrous oxide; it
is formed where there is a shortage of free oxygen. Much of the
rust in cooling jackets is black rust.

All too often, an old engine is removed from a boat, the cooling
jackets drained, and the engine stored. In most cases, there is
some sand and mud in the jackets. As the jackets dry out, the salt
is concentrated in the mud and rusting is more rapid than it was
while the engine was in use. The rust builds up on the outside of
the cylinder barrel and on the inside of the jacket. When these two
rust layers grow to the point where they meet, tremendous forces
develop and pieces are pushed off the jacket casting.

The object of this article is to tell how to reduce jacket
rusting in a stored engine and how I have repaired a damaged

When I first began restoring old marine engines for the
Chesapeake Bay Maritime Museum, I saw the damage caused by rust. As
I am retired from General Motors, I wrote the Chemistry Department
of General Motors Research Laboratories for advice. I was told to
use ethylene glycol in the jackets of stored engines, as it is a
very good rust inhibitor. It should be used full strength,
undiluted. In talking with some collectors of marine engines, I
found that this use of glycol was well known to them.

The new owner of an antique marine engine should clean out the
water jackets without delay. Some cylinders have threaded pipe
plugs where the casting cores were supported; the Palmer model ZR
is so made. Such plugs can be removed to facilitate cleaning.
However, do not hesitate to drill holes as needed to get into the
jacket. I have found two tools that are good for removing thick
rust. The first is a carbide-tipped masonry drill that can be
purchased at any hardware store.3/8 and inch are useful sizes.
Carbide drills are needed as an ordinary twist drill wears rapidly.
The second tool is a small cape chisel. A cape chisel is a cold
chisel ground on one side only, like a wood chisel, but more

If the jacket is badly cracked with pieces coming off, I cut the
jacket with an abrasive wheel to free the pieces and open the
jacket for cleaning. An abrasive wheel in a portable circular saw
works fine.

As an example, and an extreme one, I will show the repair of the
cylinder of a Palmer Model L-1 engine. The engine had been
displayed in the Oxford Museum, Oxford, Maryland, for many years.
Each time I saw it, the jacket was in worse condition. Palmer Model
L engines were introduced in 1906 and produced until 1912, when
replaced by the NL (New L). The L series was built in both single
cylinder (L-1) and multi-cylinder models. This engine has a suction
intake valve and an exposed camshaft and gears for the exhaust
valve. The main bearings are lubricated by grease cups as on
two-cycle engines. This example has a belt-driven lubricator rather
than drip oilers for the cylinder and rod bearing. That was an
extra-cost option. The history of the engine is known, and of
importance to Oxford. This may be the only Palmer L-1 existing. The
engine appeared to be all original except for the ignition timer
and crankcase breather. In 1906, Palmer Brothers made their own
timer. This engine has a Cuno timer.

At the Chesapeake Bay Maritime Museum (CBMM), we had experience
restoring such damage, so I volunteered to restore the Palmer
engine using the CBMM engine shop. By this time there were 15
pieces off the jacket and one had been lost. Figure 1 shows the
engine in the Oxford Museum before it was moved. Some of the jacket
damage can be seen near the exhaust valve spring. The cylinder
damage proved to be worse than expected. Axial thrust of the rust
had broken the cylinder barrel as shown in Figure 2. Note in Figure
2 that I had cut away some water jacket to expose the break for
welding. I next had the cylinder sandblasted where the repair was
to be made. The cylinder was arc-welded back together using welding
rod made for cast iron. Figure 3 shows the weld. In case there were
pin holes in the weld, I chipped and sand blasted the weld and
coated it with Marine-Tech epoxy putty; see Figure 4.

Next, the pieces of cast iron had to be put back. It is
important to have every surface to be cemented bright and clean. I
put them back with Marine-Tech, doing one or two per day. In most
cases, gravity and the sticky epoxy holds them in position while
the Marine-Tech sets up, but masking tape and magnets sometimes
help. Figure 5 shows the pieces in place. I mentioned that one
piece was missing. I chose a place with a similar shape and used
that place to make the fiberglass patch. I waxed that surface with
paste wax so epoxy would not bond. Then I covered the area with a
single layer of fiberglass and West-System epoxy resin. After the
patch had set, I removed it, trimmed it with tin snips, removed all
wax with lacquer thinner, and put the patch were the iron was
missing using more epoxy resin. After sanding the iron bright, I
put two layers of fiberglass cloth and epoxy resin over the entire
repaired area for added strength. Automobile body putty is useful
for filling the weave of the cloth and hiding blemishes. Figure 6
shows the repaired cylinder with a coat of primer. I had the
cylinder honed to smooth the welded area.

The engine as displayed in Oxford had been painted red, which
was never a Palmer color. There is evidence that they used dark
green on early engines and changed to a bluish grey in 1908.
Therefore I finished this engine in green, Figure 7.

Had the cylinder barrel not been broken, the restored engine
could be run. We have run some CBMM engines with similar jacket
repairs but no break in the barrel. I did not have enough
confidence in the weld of this engine to do so. However, the
cooling system will now hold glycol, and I believe the engine is
preserved for many years to come.

You can plug a hole that was drilled for cleaning in several
different ways. Probably the best way is to tap the hole with a
pipe tap, insert a cast iron pipe plug, then cut and grind it
flush. An-other way is to tap the hole with a straight thread and
then use a straight-thread plug installed with epoxy. A third way
is to repair the hole with a fiberglass patch.

Useful tools and supplies, in addition to the drills and chisel
already mentioned, are coarse 5′ sanding disks and a holder to
fit a small drill motor; a die grinder and an assortment of mounted
stones (mounted on ‘ arbors). Marine-Tech epoxy putty can be
purchased at boat yards and hardware stores. There may be other
good brands of epoxy putty. Car body putty is a polyester material
and doesn’t bond as well to metal as does epoxy. It should be
used only for filling and fairing. Spread it with a soft plastic
squeegee. West System or some other brand of epoxy resin and
fiberglass cloth can be purchased where boat paint is sold.

I would like to hear from readers who own one of the L-series
Palmer engines.

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