I pulled my boat out of storage recently and was preparing it for the summer. The oil that came out of the sterndrive was black, very black. Didn't seem to have a burnt smell though. It did have the usual nasty smell gear oil has. Last year I got lazy and didn't change the oil. I usually only put about 15-20 hours on the boat each year. I did loosen the plug to check for water, the oil did appear to be clean at that time. I have been using Amsoil Series 2000 75W-90 (full synthetic GL2 thru GL5, MT-1)for about the last 5 or 6 years.<br /><br />The owner of a local boat repair shop said that black oil is normal and not to be concerned. He did say that I should be changing it yearly though. (lesson learned). 
<br /><br />I just wanted to get some other opinions. Should I have anything to be concerned about?
<br /><br />I just wanted to get some other opinions. Should I have anything to be concerned about?