Since you aren't raw water cooled, run full strngth antifreeze down the raw water intake with engines running. Since you are FWC is a good time to check the freeze protection in your anti=freeze overflow bottle. Usually takes about 4 gallons to do each engine. Are you full fresh water cooled or 1/2 system?
Once you are done, close the seacock. I would suck any remaining raw water outof the seacock, then fill each seacock with anti=freeze, the re-connect the raw water hose. Leave the seacocks closed since you are staying in the water.
