I'm going to assume you’re in the cold country (location) since they've shut off the water. I'll explain what I have and need to do for my own diesel and you can decide from there. Mine is freshwater cooled but I'll defer for that.
You'll also want to change the oil
and filter in the engine and transmission
before you get started.
I've installed a "T" on the raw water inlet with another valve to a garden hose fitting. From that I shut off the seacock and install a garden hose up to the deck
and into a 5 gal. bucket full of water. Then open the secondary valve.
For your engine 5 gal. will be enough for winterizing for this procedure. On mine I add 3 oz. of a product called salt-away.
Start up the motor
making sure the hose has suction and run it until the bucket just empties then shut down the motor
. It should take less than a minute.
If you want to run the motor longer (without salt-away) you can run another hose into the bucket filling it while it is being used. But you don't have that option right now.
DONOT RUN A GARDEN HOSE DIRECTLY INTO THE RAW WATER INLET! Depending on the pressure it could ruin the pump.
If you don't want to install a "T" then you can just run a hose directly from your inlet.
After all this drain all the water from the engine and the lines. If you have a wetlift drain it also.
Pull the cover off your pump and the impeller from the inside and spray them all with silicon. Check the impeller. If it's in worn condition or showing any cracks and/or chips, now is a good time to get a rebuild
Loosen up the belts. Spray down the whole engine with WD-40. Change the air filter before your next startup.
You'll also want to empty out any other water on the boat (tanks and bilges) as well as the head
. Pump a little antifreeze
thru the head
in case it freezes.
One more thing if there are any cracks where water my sit and possibly freeze, seal or cover them up. Freezing water in a crack will make a bigger crack and on and on!
Got to get back to work............................._/)