Purchased a 2001 Larson with Volvo Penta 4.3l recently and took it out the first time and the boat began to fill with water. Had all hoses changed and took it out again and boat again starts to fill with water not as much as previously but it is coming in. Get it out of the water and see that the exhaust hose on the left side of the engine is melted and split. What could be causing this? Impeller was replaced as well as the water pump recently.