found this looking around myself, hope it helps
Sand will be pushed into the cooling system
by the jet pump and can cause overheating of the engine and exhaust due to restricted coolant flow. Running the ski on a flush hose will help push the sand back out of the engine. Rolling the ski over 360 degrees in the water and then starting the engine will help to remove any sand trapped in the bottom of the cylinders cooling passages. Gravel will damage the impeller, impeller housing and guide vanes in the pump. Inspect the pump and remove any gravel that is lodged in the pump
Read more: WHAT HAPPENS WHEN SAND AND GRAVEL IS SUCKED INTO... - JustAnswer
Sand will be pushed into the cooling system
by the jet pump and can cause overheating of the engine and exhaust due to restricted coolant flow. Running the ski on a flush hose will help push the sand back out of the engine. Rolling the ski over 360 degrees in the water and then starting the engine will help to remove any sand trapped in the bottom of the cylinders cooling passages. Gravel will damage the impeller, impeller housing and guide vanes in the pump. Inspect the pump and remove any gravel that is lodged in the pump
Read more: WHAT HAPPENS WHEN SAND AND GRAVEL IS SUCKED INTO... - JustAnswer