Have to Pump it Out
If the drain hose you are referring to is on the bottom left side of the engine, as you face it in the cabin, then you have to buy some type of pump to get the oil out; the drain hose is actually higher than the oil pan at the bottom of the engine and it will not flow out on its own. I have a Universal M35B on my boat and the oil can be removed either from the opening where the dipstick goes or from the drain hose. I've done it both ways and the drain hose is the better of the two.
I first bought a West Marine Oil-Vac Oil Change Pump, which worked OK once but thereafter I was not happy with. I bought a Tempo product at West Marine called the The Oil Boy Fluid Extractor Kit and have been satisfied with its performance. It has a five-quart capacity. There are a number of this type of product in addition to the two I've mentioned.
The product provides directions but you basically insert a rigid plastic tube up into the drain hose as far as it will go, then connect the hose to the pump, then pump out the oil per the instructions.