40021 Ben Morgan Road Leonardtown, Maryland 20650 Copyright
Setting the cam gear on the YT-1 marine engine can be a most
difficult problem when tackled for the first time. The gear being
spiral means one has to take into account the initial mesh versus
the final mesh rotation of the cam. Hopefully the following
approach should avoid too many frustrating attempts to correctly
time the valves.
1. The rotation of the YT-1 is counter clockwise facing the
flywheel. Too many people have tried to start the YT-1 or other old
time marine engines by cranking them clockwise. The common
experience is the engine keeps backfiring and wants to run the
other way, NUFF SAID!!!
2. The water pump eccentric if lightly pressed on the shaft
makes a convenient hand-hold to rotate the cam.
3. Note the key ways on the shaft all line up.
4. Slide the water pump end bushing onto the shaft and then
insert the keys in the shaft for holding the cam gear.
5. Note the cam gear key ways are lined up so that the
peak of the exhaust valve cam is lined up with its keyway. The
intake cam peak clearly does not line up with its keyway. The
exhaust cam should be installed toward the water pump
For our marine friends the water pump and the exhaust valve are
on. the Starboard side of the engine. The intake valve is on the
Port side of the engine.
6. If one holds the cam gear in their hand with the
keyways facing away and the exhaust cam end toward the right, one
should note the intake cam on the left end is in the same relative
position as the exhaust cam peak except it faces toward the rear.
Rotating the cam gear clockwise (relative to the exhaust cam)
should indicate the closing of the exhaust valve immediately
followed by the opening of the intake valve.
7. There is often a large overlap in the opening of the
typical exhaust valve and the closing of the intake valve. On the
other hand most old time, low speed engines with mechanically
operated valves are very predictable on the closing of the exhaust
valve followed within a few degrees with the opening of the intake
valve. For this reason one should work with the closing of the
exhaust valve followed by the opening of the intake valve.
8. One can visualize the YT-1 cam gear when it is
correctly positioned in the engine with the keyway of the water
pump eccentric facing forward, the exhaust valve will have just
closed and the intake beginning to open.
9. When the flywheel rotates counter clock wise the cam
shaft rotates clockwise when viewed from the water pump end of the
shaft. The trick is to insert the cam gear with the exhaust cam
towards the water pump so when the flywheel is pulled up on TOP
DEAD CENTER the water pump eccentric keyway faces forward. There
can be no question if one has the gears meshed correctly. Check the
position of the piston through the spark plug hole. As the piston
comes up on TDC the exhaust valve closes and the intake begins to
open. Being off by one tooth in either direction will immediately
be obvious. The really frustrating part of the operation is judging
how much lead in meshing the spiral gear. Once you know how to
determine the exhaust cam end and the final position of the cam
shaft key-ways at TDC, persistence will overcome one’s
10. Once the valves are timed correctly it is a simple
matter to time the ignition. Bring the piston up on TDC of the
FIRING stroke. The Cuno timer drive shaft has a flat milled on it.
The flat on the drive shaft should face aft when the piston is on
TDC of the firing stroke. There is a -20 thd set screw that is in
line with the flat on the drive shaft. By observing the relative
position of the set screw one can determine the position of the
internal wiper of the timer without removing the timer cover. With
the flat facing aft the timer should be at mid range for
advance/retard. Moving the timer handle towards the flywheel
retards the spark.
11. To start the YT-1 put a few drops of gasoline in the
priming cup. Set the timer handle straight up. Pull the flywheel up
SMARTLY and the engine should normally start on the first pull.
Once the engine starts, advance the spark and set the throttle. The
typical YT-1 idles at about 150-180 rpm. The drip oilier should be
set for about six drops a minute as it is the prime means of
lubricating the forward portion of the crankshaft.