ETC-Era Pontiac Marine Engines

ETC-Era Pontiac Marine Engines
The seller in this recent auction provided 74 photographs of the engine and I found them to be quite
interesting. I am somewhat familiar with marine
engines, having been trained on a wide variety of
them in the Navy. I also owned a 26’ Lyman for
several years powered by an inboard Chevrolet 350
V-8 conversion from Crusader Marine.
The primary changes from automobile to marine
use involve the cooling system and addition of a water-cooled exhaust manifold. Since the boat is floating in an unlimited supply of water, marine engines
can be water cooled without the use of an automotive type water to air radiator. This is especially true
for fresh water applications. Marine engines have a
“raw” water pump that brings in cooling water from
under the boat. It is a centrifugal type pump with
an impeller, just like an automotive water pump. It
is usually mounted low, under the boat’s waterline,
so the pump housing will always be full of water. If
mounted above the waterline, the suction side
needs a check valve so the pump does not loose its
prime. The raw water pump has sufficient capacity
to provide cooling water for the engine cooling system plus the exhaust manifold; any extra water is
dumped into the exhaust pipe where it connects to
the manifold and flows out with the exhaust. This is
a one-pass system, all of the water is discharged out
the engine exhaust after flowing through the engine.
Arn Landvoigt brought this subject to me several
years ago after having come across a Pontiac splithead 6 cylinder converted by Gray Marine for use in
a 1931 Chris Craft. Gray Marine built engines for
years, but began converting automobile engines in
1927. So far, Arn has identified 4 split-head six conversions from Gray; the 6-27 from 1927, the 6-40
from 1927-28, the 6-41 from 1928 and the 6-63 dating from 1931-32.
Generator/starter side of Gray Marine engine,
the flywheel housing is on the right.
He recently sent me a link to an E-bay auction of a
Kermath Sea Chief Eight, which was based upon the
Pontiac straight 8. I did a bit of research and Kermath used Pontiac L-head straight sixes and eights
for marine conversion, apparently under the Sea
Chief name, although this name was also applied to
engines from other companies as well.
The raw water pump & pulley below the harmonic balancer. The hose under the generator is the suction line. The v-belt drives the
generator and raw water pump, the engine
water pump has no pulley and did not turn.
Carburetor side, note the crankcase breather
tube just in front of the carburetor flame arrestor. The fuel pump is also shown. The
transmission is on the right.
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Salt-water applications can be done the same
way, but quality marine conversions will utilize some
type of water to water heat exchanger because saltwater is very corrosive. Automotive engine conversions typically use a header tank system that keeps
the raw water separate from engine cooling water.
The engine cooling system is sealed and water circulates to the sealed side of the header tank and back
again. The raw water side of the unit discharges
water to the exhaust manifold for cooling. It may
also have a dedicated overboard discharge pipe, if
extra cooling capacity is necessary.
You can barely see the raw water pump discharge line at the lower left of the balancer.
The fitting on the timing cover mounts a cable
to drive a tachometer. Raw water enters the
exhaust manifold at the other end, at this end
you can see the fittings that connect to the engine water pump. The raw water pump provides the circulation, the engine pump serves
as a hose connection and directs the water into
the distribution tube. The cooling water is being warmed by the exhaust before entering the
engine. Knowing what a cylinder head looks
like under the Pontiac thermostat housing, and
noting how short this water outlet is, I doubt
this engine is fitted with a thermostat.
Kermath Sea Chief 8 water outlet, you can
just see “outlet” by the hose nipple.
Since engines are more efficient when running at
operating temperature, marine conversions are fitted with one, and often two thermostats. The thermostat works just as it does in an automobile, restricting the flow of water until its design temperature is reached. During low speed or at economy
cruise RPM, minimal engine heat is generated and
water flow through a single thermostat is sufficient.
But unlike automobiles, boats can be operated at
high speeds for hours on end. In marine applications, engines are also rated for maximum continuous RPM, at these high speed and power levels
much more heat is generated, whereby the second
thermostat will open and increase the flow of cooling water. In applications where salt-water is actually circulating in the engine, lower temperature
thermostats are used to help minimize corrosion
damage.
There can be another significant difference when
automotive engines are adapted for marine use, especially for installation in smaller pleasure boats
where the engine is under the deck. The crankshaft
will be much closer to the bottom of the boat if you
take power from the front (timing case) of the engine. The engine / transmission unit is narrow
enough to fit deep between the stringers (hull structural members that run fore & aft, parallel to the
keel). The conversion company would design its
own housing to cover the timing case and mount
the transmission. A coupler would be needed to
connect the crankshaft to the transmission, which
would possibly include a torsional damper since the
original harmonic balancer was probably unsuitable.
The automotive water pump could be replaced with
appropriate hose connections, the raw water pump
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would provide the necessary circulation and often
the generator would be converted to a geared or
chain drive on the redesigned timing case for ultimate durability.
Since power is taken from the front, an enclosed
flywheel housing is needed, usually fitted with rubber cushioned mounts that lag bolted on the top of
adjacent stringers. The starter can be mounted high
and dry, away from bilge water and accessible for
service. Some conversion companies installed a pulley on the flywheel hub and mounted a belt driven
generator on the housing as well.
Inline engines were typically fitted with an updraft
carburetor, by mounting it under the manifold a very
low profile could be maintained. It was not uncommon for marine engines to have dual carburetors for
increased power. A mechanical fuel pump was typical, but likely to be inverted for access to the sediment bowl and fitting connections.
Crankcase ventilation was needed but the automobile road draft tube was unacceptable in the enclosed engine bay of a boat. Typically the original
valve chamber (side) covers would be replaced, one
fitted with an inlet breather and the other fitted with
a metal outlet tube that would rest directly on the
carburetor flame arrestor. Air rushing into the carburetor would create a suction on the ventilation
tube and draw fumes from the crankcase.
Arn and I would appreciate hearing from any of
you that have additional information regarding nonautomotive applications using Pontiac engines.
Thanks to this shot of the cylinder head casting
number, we know this is a 1950-51 engine.
The distributor, octane selector and plug wire
manifold are stock Pontiac units. Note the
unique oil fill tube and sealed fill cap.
The bright object is the top of the fuel pump,
the dirty square is the flame arrestor. The
carburetor is a single barrel updraft unit.
The engine water pump, casting No 511244
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The photo at left is tilted to the left, it shows the
back of the block and head. The lower left corner is
an aftermarket oil filter and connecting tubing. Just
to the left of where the tubing disappears is a hose
and clamp, it is the raw water connection to the exhaust manifold. The large rounded piece above the
hose connection has lettering on it, but even greatly
enlarged I could not make any sense of it.
To the left of the hose connection and lettered
component is what appears to be a tube, possibly a
crankcase vent from the rear side cover. Unfortunately the engine was sitting next to a wall, so there
were no good photos of the carburetor side of it.
The photo below was taken looking down, it
shows the top of the oil filter, the exhaust pipe with
a cooling water connection and the top of the transmission with engine I.D. tag and finally the starter.
The bottom photo shows the starter, cables and
electric solenoid switch. This starter has a Bendix
drive as opposed to Delco type shift solenoid.
The Kermath company was a well respected name
in marine engines. They introduced the Sea Wolf series in 1926, which featured a single overhead camshaft; hemispherical, 4-valve combustion chambers;
and a 12 spark plug, dual ignition system. It displaced 648 cubic inches and was rated for 150 horsepower @ 1,800 RPM. By late 1929, this engine had
grown to 678 cid and 225 horsepower.
The fine print on the tag recommends S.A.E 30 in
summer and S.A.E. 20 in winter. The valve clearance
specification was .010 on the intake and .012 for the
exhaust. I would have liked to know if the Kermath
serial number was the same as the number Pontiac
stamped on the engine block. The Code on the tag is
PEBM 7. I wonder if PEBM stood for Pontiac Engine
Block Marine. We will probably never know.
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