Winterize an inboard boat by gathering the primary materials and tools, changing the oil, cleaning the carb, draining the coolant, and lubing the lower unit. As of 2015, doing all of this yourself can save $150 off of the cost of winterizing.
The necessary materials to begin winterizing the boat include a can of fogging oil, multiple gallons of antifreeze, an oil filter and motor oil, drain plug gaskets, and lower unit lube. You also need an oil-suction pump and a lower-unit lube injection pump. Finally, gather sockets, screwdrivers and combination wrenches.
The next step is to change the oil. Begin by sucking out the oil and changing the filter. Next, fill the gas tanks with non-oxygenated fuel and add a marine fuel stabilizer to your tank. Bring the boat to the landing, and remove the spark arrester from your carburetor while the boat is in the water. Next, fog the engine and bring the boat onto land.
Tip the trailer up, place a bucket beneath your hull drain plug, and then remove the plug. Remove the drain plugs, and begin draining near the top of the engines. Next, reinstall other hoses and plugs but leave the block drain plugs out. Remove the thermostat, and pour in the RV antifreeze until it is draining out of the block drains. When it is done, reinstall the drains and plug.
Finally, unscrew the lower unit's bottom drain plug and let it drain several minutes before removing the plug for the upper vent. Refill with fresh lube, and cover the boat to finish the winterizing process.