Many popular boat sites recommend leaving the system drained because “air doesn’t freeze”. On the other hand marine engine antifreeze contains water which promotes corrosion.
Where do you pour antifreeze in a boat?
Pour RV antifreeze directly into the thermostat opening or into the large hose attached to it. Keep pouring until you see a steady stream of the pink stuff running out of the block drain plug. Tip the trailer up (so it drains well) and place a bucket under the hull drain plug.
How do you fill a boat with coolant?
Open the coolant fill cap at the top of the engine if the flow is low. Drain the engine. If the drain pan gets full, close the plug, empty the pan into the waste storage jugs, then replace it under the drain and continue.
Do you need to put antifreeze in an inboard motor?
Adding Antifreeze and Fogging Oil to an Inboard engine
Warm the engine up to operating temperature, just like with a sterndrive. … Have additional antifreeze handy if you know your boat takes more than that or if you’ve never winterized before. You can use any leftovers in the boat’s plumbing systems.