When I turn on my a/c I always check to make sure there is a steady stream of water coming out of the boat. About a month ago there was no water coming out. I took off the hose going from the pump to the a/c and blew through it - sure enough it was clogged. I was able to clear the clog by blowing very hard into the hose. Then everything worked fine. A couple weeks later the same thing happened, with the same results. Last week I was at a marina and got the a/c going about 3 pm, with water flowing as normal. However, at 1 am the a/c quit, and the impeller on the water pump appeared to have failed. To get a/c for the rest of the night I bypassed the pump with a water hose, and the a/c worked fine after that. So now the question is - what could have caused the blockage? Why did the clog reappear at 1 am with the a/c running normally for several hours? Why was I able to clear it? My mechanic will be replacing the impeller today, and he is going to run a solution through the system to get rid of algae, etc. I'm not confident that will fix the problem since I don't see how an algae can stop the system once it's working. However, as you can imagine, I don't want to go through this again. Your thoughts would be appreciated.