In that case you need an air compressor, hose and sea strainer top adapter. You need to blow the strainer and all the water out thru the bottom of the hull.
The ball valve gets closed and remove the top of the sea strainer. Install the adapter on the sea strainer with an air chuck fitting and turn pressure down to 20 to 30 psi. Open the hull sea valve, then open air valve which will push all the water out of the sea strainer and out thru the hull. Close the hull valve and then shut off air.
Next either need to drain all the water from the sea water pump, heat exchanger and mufflers, or get 5 gallons of antifreeze and pour in a bucket. Remove the hose coming from the sea strainer going to the motor. Stick the hose in the bucket an start the motor. Once the bucket gets empty the motor should be winterized and you should have seen pink coming out the exhaust, if they are above the water.
If motors are carbureted you can start spraying fog oil just as the antifreeze is getting close to running out. If they are MPI and you want to fog, might see if
tpenfield can advise on mixing fuel/oil to use prior to oil change and winterizing
