I recently bought a new boat with a 75hp Mercury 4 stroke and have had a great time with it. Two days ago I decided to flush out the motor. According to the Mercury book that came with it, you just hook up your garden hose to the back of the engine and turn on the water, then start the engine. Well I did that and only saw water trickling out by the prop. I immediately turned off the engine and called the dealer. The dealer said that the book is wrong and that you have to use the ear muffs on the lower unit. I went and got a set of the ear muffs and put them on the lower unit, turned water on, then the engine. Still no water was coming out of the hole in the back of the engine. This morning I noticed that the hole was clogged with sand and debris. I called my friend and he was like, oh yeah I forgot to tell you that you should make sure that was free of debris and to get some weed eater string to punch out that tube. Well I proceeded to do that and had about a shot glass of sand come out of the engine. I am so glad that I decided to flush it out before this weekend. Otherwise my engine would have overheated and I would have been stuck out there, trolling back for god knows how long. I learned a very good lesson and wanted to pass this on. I am sure most people know to look for this but, I just assumed, New Motor, what could go wrong. Turns out I was wrong but I am glad I caught it in time.