Here's what the Yanmar manual says about storage.
If the engine will not be used for an extended
period of time, special measures should be
taken to protect the cooling
system and combustion chamber from
and the exterior from rusting.
The engine can normally stand idle for up to
6 months. If it remains unused for longer
than this, please contact your authorized
dealer or distributor. HUH?
In cold temperatures or before long-term
storage, be sure to drain the seawater from
the cooling system.
WARNING! NEVER remove the coolant
filler cap if the engine is hot. Steam and
hot engine coolant will spray out and
seriously burn you. Allow the engine to
cool down before you attempt to remove
the cap. DUH!
CAUTION! DO NOT drain the coolant
system. A full coolant system will
and frost damage.
CAUTION! If seawater is left inside of the
engine, it may freeze and damage parts
of the cooling system when the ambient
temperature is below 0°C (32°F).
PREPARE ENGINE FOR
Note: If the engine is close to a periodic
interval, perform those
procedures before putting the
engine into long-term storage.
1. Wipe off any dust or oil from the outside
2. Drain water
from fuel filters.
3. Drain fuel tank
completely or fill the tank
to prevent condensation
. (Small portable tanks)
4. Grease the exposed areas and joints of
bearings of the remote
5. Seal the intake silencer, exhaust pipe,
etc. to prevent moisture or
contamination from entering engine.
6. Completely drain bilge
7. Waterproof the engine room to prevent
rain or seawater from entering. N/A
8. Charge the battery
once a month to
compensate for battery’s selfdischarge. N/A
9. Remove key from key switch and cover
the key switch with moisture cap. N/A
Note: The drain cocks are opened before
from the factory. Marine gear
ZF25A does not have a drain cock on the
NOTICE: If seawater is left inside, it may
freeze and damage parts of the cooling
system (heat exchanger, seawater
pump, etc.) when ambient temperature
is below 32°F (0°C).
1. Open the seawater drain cock on the
cooler (if equipped). Allow to
drain. Open the seawater drain cock on
the intercooler (4JH4-HTE only) and
drain. If no water
drains, use a stiff
brush to remove any debris.
2. Remove four bolts attaching the side
cover of the seawater pump. Remove
the cover and drain the seawater.
3. Install cover and tighten bolts.
4. Close all the drain cocks.
RETURNING THE ENGINE
1. Replace the oil and the oil filter
running the engine.
2. Supply fuel if the fuel in the fuel tank was
removed, and prime the fuel system.
3. Confirm that there is engine coolant in
4. Operate the engine at idle speed for 1
5. Check fluid levels and check engine for
For my winterizing procedure I remove the impeller from the raw water pump
I've also heard that one should remove the injectors and squirt motor
oil in and crank over a few turns. But I would think leaving the exhaust hose off and cranking the motor over every 3-6 months should be OK.