The YT-1 and YT-2 Marine Engines

By Staff
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YT-1 1922-1924 style intake 1938 engine.
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YT-1 1924-40 style intake 1922 engine.
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A Palmer built heavy duty engine in a small package, suitable for small boats of all kinds, both commercial and pleasure craft; also as auxiliary for small sail boats. Standard with timer. Available with clutch or magneto.
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YT-1 1940 style intake 1947 engine.
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YT-1 1998 made from N.O.S.

Jr. 40021 Ben Morgan Road Leonardtown, Maryland 20650-2521.
Copyright retained.

In my opinion, the two most sought-after antique marine engines
are the Palmer Bros, of Cos Cob, Connecticut, models YT-1 and YT-2.
The YT stood for ‘Yacht Tender.’ They were widely used in
that application, but they also were popular with working watermen.
These engines are beautifully running at very low speed, small,
lightweight, and it’s fun to watch all the motion. They have
exposed overhead valves and an exposed eccentric and strap
operating the water pump plunger. A few have magnetos but most have
Cuno timers with T Ford ‘Buzz’ coils for ignition.

Around the Chesapeake Bay, the YT-1 was a popular engine for
small crabbing skiffs. This was probably due to the much better
fuel consumption of a four-cycle engine over the turn of the
century two-cycle engines that had powered many of the watercraft
favored by the watermen.

The YT-1 was released for sale in December 1921 and was made
until 1947. By the 1920s the watermen were replacing their
two-cycle engines with new four-cycle engines as most of the early
engines were long since beyond reasonable repair. On the other
hand, the two-cycle marine engine with make and break ignition held
on in the Canadian Maritimes up until at least the mid-1960s. I
believe this was due in a major part to the area weather
conditions, and often the watermen had essentially open boats. The
proven reliability of the low voltage make and break ignition over
jump spark under adverse weather conditions demanded a waterman
stick with proven technology. It is true four-cycle marine engines
were made with make and break ignition, however I don’t believe
they were commonly made after the early 1930s, particularly in the
sizes needed by watermen. A two-cycle M&B marine engine is
still made in limited production in Lunenburg, Nova Scotia.

The ignition system was the most troublesome portion of the
marine engine. Dampness and water, particularly salt water,
corrosion were two very active participants in the daily lives of
watermen. One of the ways watermen dealt with these two very
troublesome problems was they would put the ‘Buzz’ or
M&B coil along with the battery in a small wooden box. The
cover or lid was arranged so water would not run into the box. The
two or three wires to the engine would be lead out of the box with
the holes for the wires slanted down so water could not run down
the wires into the box. Often the box would have a leather strap
which the waterman could slip over his shoulder so he could carry
the box home and put it by the kitchen stove to dry out during the
night. This same setup is also great for running marine engines at

The YT-1 developed 2 HP at 800 rpm. It swung a three-blade,
12′ diameter by 10′ pitch prop, weight 130 lbs., bore
3′, stroke 3?.’ There were two flywheel diameters. Some
early YT’s had flywheels 11′ diameter, and later units had
12′ diameter flywheels.

In 1936 the YT-1 cost $ 100, magneto $35 extra, clutch $45
extra. Needless to say, most watermen bought them without the
clutch or magneto.

Only one out of thirteen known YT-1 engines has a magneto. On
the other hand, three out of four known YT-2’s have magnetos.
Apparently YT-2’s tended to be bought by more affluent
yachtsmen, rather than watermen. That may be the explanation for
more magnetos on YT-2’s than on YT-1’s. I doubt we shall
ever know the answer.

The YT-2 was essentially two YT-1’s mounted back to back on
one crank-case. It was made from 1924 until about 1928. Of the four
YT-2’s known to the author, three have 1924 manufacturing dates
and one has no serial number. The last two digits of Palmer Bros,
engine serial numbers are the year the engine was made. In the late
1960-1973 time frame, only the last digit is the year the engine
was made. Considering that engines such as the Palmer Model C were
made from 1900-1930 with very few changes, it is not possible to
precisely identify the year of manufacture without the original
serial number tag.

The YT-2 sales price is unknown. Trim such as carburetor, water
pump, priming cups and drain cocks were the same as for the YT-1.
Parts such as valves, valve springs, push rods, water pump,
eccentric, etc. were the same as the YT-1. The cylinder head for
YT-1 ‘s made before 1924 had the spark plug facing aft at about
45 degrees. Because the spark plugs would interfere in the YT-2,
the plugs had to be placed in a vertical orientation. This meant
that YT-l’s made after 1924 have their plugs vertical. Early
YT’s had 7/8‘ spark plugs, later
YT’s had 18mm plugs.

The YT-2 has an oil pump driven off the aft cylinder camshaft.
It pumps oil to the forward crankshaft bearing from the aft sump.
In the YT-1 the forward crankshaft bearing is oiled by a drip oiler
and the crankcase is splash oiled in both the YT-1 and YT-2.

The magnetos for the YT-1 and YT-2 were American Bosch model
FX-1 or 2 or FB-2ED-1-1c. Remember the YT-1 and 2 run
counterclockwise facing the flywheel and the YT-2 fires at 90

There were basically three different carburetors and intake
manifolds used on the YT-1. The 3/4 inch
Schebler Model D was used with the intake manifold shown in the
photo marked 1922-1924. While the Schebler model was the standard
carburetor offered by Palmer, individual owners may have tried
other carburetors such as Kingston five ball, Krice, Monarch, etc.
These owners were probably trying to get more speed or better fuel

The Mayer carburetor with an SAE style flange was used with
intake manifold shown in the photo marked 1924-1940. It is believed
the Mayer carburetor started out on the 1914 Buick automobile.


Bore and Stroke 3′ x 39?’
Displacement, cu. inches 25
Weight, lbs. 130
Dimensions, Length overall, ins 18
Width overall, ins 12 ?
Width between timbers, ins 8
Width between bolt centers, ins 11?
Height, center of shaft to top of rockers, ins 17 ?
Depth, center of shaft to rim of flywheel, ins 6

CYLINDER–Special gray iron, ground and honed
to size, ample cooling surface, intake pipe cast integral to heat

CYLINDER HEAD–Removable type, water

VALVES–Incorporated in head, interchangeable,
non – corrosive steel.

PISTON–Hard gray iron, liberal length, fitted
with three rings.

WRIST PIN–Carbon steel hardened and ground,
hollow, full floating.

CONNECTING ROD — Drop – forged, I beam
construction, bronze back babbitted die cost bearings, nickel steel
connecting rod bolts.

CRANK SHAFT–Drop-forged, counterbalanced, heat
treated and ground.

BASE–Cast-iron, barrel type.

CRANK SHAFT BEARINGS–Bronze bock, babbitt

CAMSHAFT–Drop – forged, with gears and corns
integral, hardened and ground, bronze bearings.

ROCKER ARMS–Standard design, drop-forged,
bronze bushed.

PUSH RODS–Steel, adjustable! fitted with boll
and socket.

BALANCE WHEEL–Gray iron costing, machined to
size, balanced, taper bored and keyed to crank shaft.

EXHAUST AND INTAKE–Exhaust outlet flanged to
cylinder head and topped for 1′ standard pipe. Intake cost
integral with cylinder forming hot spot, flanged for

WATER PUMP–Bronze, plunger type, eccentric

IGNITION–Coil and timer for use with 6 volt
battery is standard. Magneto may be supplied at additional

Available as extra equipment with machined sub base costing if

With the passing of the Safe Boating Act in 1940, the Zenith
marine carburetor, 61 series, was used. See photo marked 1940
intake. This carburetor is slightly different from the Zenith
industrial version in that it has an intake throat slanted upward
to keep gasoline from running out. when ‘choking’ the
engine to start. A gasoline pickup tube, to clear the throat once
the engine starts, is included. Provision to mount the backfire
trap on the inlet to the throat is made. The industrial or marine
carburetor works equally well, but DON’T use the industrial
carburetor in a boat.

The photo showing the 1940 intake manifold should be compared
with the photo showing the 1924-1940 intake flange. On occasion the
carburetor end flange on the 1924-1940 manifold will be found with
the holes slotted out to take the larger flange on the later Zenith
61 carburetor.

This damage may easily be overcome by filling in the slots with
braze and reshaping and redrilling the flange. Some intake
manifolds will be found where the carburetor does not sit level
when the engine is sitting level. This is because to engine angle
in the boat had necessitated bending the manifold to allow the
carburetor to sit relatively level in the boat.

It is interesting to note Palmer catalogs of the period show a
?’ pipe thread/SAE style flange with the Shebler, model D
connected with a ‘close’ nipple without an external pipe as
shown in the photo of the YT-1 made in 1998 from N.O.S. parts. This
photo also shows the cast iron breather valve of the late 1930s and
the expanded crankshaft boss of 1937. This boss permitted the use
of modern LIP seals in place of the felt seals that had been in use
before the invention of the LIP seal.

The felt seal had the serious drawback of absorbing the water
and eroding the crankshaft. The change to LIP seals took place in
1937. A suitable replacement seal is Federal Mogul 476838.

It appears most YT-1 applications were without reverse gears. In
the case of the four known YT-2’s one had a Palmer-made base
using a Joe Petrolli, so called ‘Navy gear.’ The other YT-2
with reverse gear has a Palmer model YC reverse gear.

There are a few other changes that will help to roughly date a
YT-1 without a serial number. It may be noted that the 1922 engine
serial number tag is located on the forward face of the cylinder
just behind the drip oiler. Some time after 1924 Palmer began the
practice of placing the serial number tag on the port crankcase
mounting wing just aft of the carburetor. When the practice of
placing the serial number tag off the cylinder (in a location not
so easily lost, if the cylinder is replaced) began is not known at
this time.

It is believed that a petcock was added to the aft starboard
side of the crankcase to indicate correct oil level in the
crankcase in about 1926.

It will be noted on the 1938 and 1947 engines there is a
mounting bracket with a hole bored in it just behind the sector
bracket of the Cuno timer. This seems to have appeared when the
YT-2 was released for sale in 1924. This mounting bracket is cast
into the crankcase and is used to mount the magneto gearbox. It
should be noted that when the magneto is used, the camshaft has to
be changed from the one used with the Cuno timer. The magneto drive
bracket is not present on the 1922 YT-1.

There were a number of water outlet changes made on the cylinder
head. The first version exhaust outlet was a 1′ NPT boss.
Cooling water discharge was a 3/8‘ NPT
out the top of the head. When the YT-2 was released for sale, the
exhaust boss was changed to a semi-triangular shape with
5/16‘ cap screws to hold the exhaust
manifold against the two cylinder heads. Cooling water for the
exhaust manifold passed from the cylinder heads into the exhaust
manifold water jacket through 3/8‘ holes
near the apex of the triangle. In the YT-1 application, the
cylinder head had the same semi-triangular shaped boss, only in
this case an adapter was provided having the same general shape as
the exhaust boss. The adapter was approximately 1′ thick and
bored for 1’ NPT exhaust pipe. The cooling water discharge was
a 3/8‘ NPT in the top of the adapter
which was, at some later date, changed to the cylinder head.

There were three types of crankcase breather valves. A mushroom
style and a later cast iron unit shown on the ‘1998’ engine
replaced a small bronze check valve that dated back to at least the
1912 period. The purpose of the crankcase check valve in a one
cylinder, closed crankcase four-cycle engine is to keep the oil in
the crankcase from being forced out of any small opening such as
around the valve tappets, crankshaft or camshaft bearings.

When the piston comes down it compresses the air in the
crankcase unless there is a working check valve to allow the air to
escape. When the piston rises, the check valve closes and a vacuum
is created in the crankcase thus keeping the oil from leaking out
of the engine. I have stressed working check valves because these
valves tend to become dirty and sluggish in operation and while the
engine runs well, it is going to lose oil at a rapid rate.

The cast iron breather needs to be cleaned occasionally. It is
not as complicated as will appear on first inspection. There is a
bronze valve that moves up and down with the piston motion. On the
top side of the valve is a small piston that slides in and out of
the top cap. There is a small phosphor bronze spring on top of the
piston which returns the valve to the lower bumper. Don’t lose

Immediately below the valve is a threaded rod with a neoprene
bumper washer that limits the travel of the valve. This rod is
extended through the bottom of the breather and it has a lock nut
that keeps the rod from moving once it is locked down. When
operating correctly there is a definite clapping sound. To adjust,
loosen the lock nut and rotate the threaded shaft either way until
the valve starts to ‘clap.’

The simple old time bronze two-part check valve made far less
noise, and if one can find one of them, they bolt to the same bolt
spacing as the cast iron unit. Don’t toss out the cast iron
unit, as it would depreciate the value of the engine as an

In conclusion, the author is constantly looking for differences
in various early Palmer Bros, engines. It is most helpful if photos
of all four sides are taken and serial numbers provided if

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