Yanmar 1GM10 Operation Manual page 13

SAFETY
12/05
If you have an installation with two or three
engines and only one engine is operating,
the water pickup (thru-hull) of the
non-running engine(s) should be closed.
This will prevent water from being forced
past the seawater pump and eventually
finding its way into the engine. The result
of water entering the engine could cause
seizure or other serious problems.
If you have an installation with two or three
engines, and only one engine is operating,
please note that if the propeller shaft
thru-hull (stuffing box) is lubricated by
engine water pressure and the engines are
interconnected, care must be taken that
water from the running engine does not
enter the exhaust of the non-running
engine(s). This water could cause seizure
of the non-running engine(s). Consult
authorized Yanmar Marine dealer or
distributor for a complete explanation of
this condition.
If you have an installation with two or three
engines, and only one engine is operating,
it is important to limit the amount of throttle
applied to the running engine. If you
observe black smoke or movement of the
throttle does not increase engine speed,
you are overloading the engine that is
running. Immediately throttle back to
approximately 2/3 throttle or to a setting
where the engine performs normally.
Failure to do so may cause the running
engine to overheat or cause excess
carbon buildup which may shorten the
engine's life.
Never turn off the battery switch (if
equipped) or short the battery cables
during operation. Damage to the electrical
system will result.
7
GM Series Operation Manual