The newer engines have a drain hose for changing crankcase oil. Refill crankcase with new oil and replace filler cap. Run engine again for about 5 minutes to distribute a protective film of clean oil to act as a rust preventive during storage. You may just add to the existing oil or drain the old oil and completely refill with new transmission oil. Be sure both drain and filler plugs are tight after draining or adding to the oil in the transmission.
Transmission is now ready for storage.
To drain sea water system, disconnect hose end at sea water pump that comes from heat exchanger. Lower free end of hose to a point approximately level with the front engine mount. This will allow the sea water to drain from heat exchanger and hoses. Loosen the 4 or 6 screws on the sea water pump cover plate. Tap the plate lightly to loosen it, this will allow pump to drain.