I'm not really all that familiar with the O'Day 20 but if it's like the O'Day 222, the hoses are probably clear vinyl 5/8" hose that can be bought in any hardware store. The sink drain hose probably comes out of the drain in the sink and through a compartment under the V birth and out through a thru-hull fitting on the bow. The intake hose for the pump faucet probably takes part of that same route and goes into a 5 gallon water container under the V birth section. It's a very simple hook up if everything is there including the removable water tank. If you replace the hoses, make sure that you make the pump hose the same length as the old hose. It needs to have water in the hose to get it's prime for the pump to work.
Joe