Here is how I winterize my '89 Sea Ray with twin Mercruiser 5.7's and Alpha 1 drives. No need to start the engine, have the thermostat open or pull the thermostat. - Drain the manifolds and risers and leave the drain open. There may be 1, 3 or no drains, just the hose depending on the year. - Drain the engine block, first one side then the other. Poke with a wire to move the scale to get it started. When the water stops, don't assume it is drained. It may be clogged. Poke again, and again. - Pull the 6 hoses off the thermostat housing - Pull the lower hose off where it attaches to the water pump, let a slug of water out, reattach and tighten. - Close one block drain. Leave other open. - Pour not toxic antifreeze in the top of the water pump hose until you see pink coming out the drain. You did tighten the lower, right. - Close that block drain and repeat with the other side and close. - Pour antifreeze into the water pump hose until it comes out the thermostat housing port where the water pump hose was connected. Hold the hose equal or higher than where it connects. It will take about 2 gal. The thermostat does not have to be open. Here is why: You are pouring into the water pump. Water goes from the pump into the block then out of the block up to the thermostat housing and, if the engine is cold, back to the water pump. So there is no need to remove the thermostat. If you doubt this, look carefully at the Sea Ray thermostat housing flow diagram or just try it. If the thermostat is open antifreeze will come out the exhaust manifold and water pump ports on the housing. Remember - pour into the water pump. People get in trouble when they pour into the exhaust manifold port. That only works if the thermostat is open. If closed, the antifreeze doesn't go into the block. Or, they pour into the riser hose and the balls block the antifreeze. - Pour antifreeze into the riser hose until you see pink coming out the manifold drain, close manifold drain or reconnect hose if no drain and pour some into the riser and manifold hoses and into the riser and manifold ports on the thermostat housing. Reconnect all hoses. - Disconnect the sterndrive water intake hose under the engine where it connects to the power steering cooler. Hold low and let a slug of water out. Hold the end of the hose high enough so that it is higher than where the hose connects to the transom. A funnel helps. Pour antifreeze in until pink comes out the outdrive. Doesn't take much. If you are alone, just look for pink on the intake of the drive. If the hose fills up and doesn't drain, turn the engine over just a bump, half a revolution, to move the water pump vane in the sterndrive from blocking its port. You can turn the engine by hand if the battery is out. I've not found it necessary to bump the engine. Reattach the intake hose. - If your engine has hoses going from the water pump to the hotwater heater, disconnect at the water pump, and hold lower than the heater to drain them. - Make sure you have reconnected all the hoses correctly and tightened. That's it. You are done. It really doesn't take long. One person can do it alone. Only takes 3-4 gal. and, you positively know the block is full of antifreeze. I used to winterize running antifreeze through the muffs. Now the EPA says we can't let non-toxic antifreeze on the ground which means we need to collect the antifreeze coming out of the outdrive when running the engine - a pain. Also, one year an engine overheated using a winterizing kit with a tank on the swim platform.