I have a 2000 year Yamaha T-50 (4 stroke, high thrust) that has gas in the oil. The engine has about 125 hours on it now and has very little use in the past two years. I winterize it myself at which time I fog the engine, change the oil and filter, etc.<br /><br />Last summer, I went to check the oil and noticed the oil seemed thin, a little overfilled, and smelled of gas. I changed the oil and didn't think too much more about it it. In the fall, I changed the oil when laying up for the winter and didn't notice (but wasn't really thinking too much more about it) any gas in the oil at that time.<br /><br />This summer, after only a few hours of use, I checked the oil and noticed it was thinned out and smelled of gas.<br /><br />After reading some of the posts here and on other sites, I'm very concerned that I have a major problem, possibly with the rings. I don't beleive this was going on the first couple of years of ownership. Also, I did break the engine as specified in the owners manual. So I'm thinking the rings did get seated properly.<br /><br />The one thing that has been different is I have started to store the boat with the vent cap on the gas tank closed thinking it cut down on fumes in the garage.<br /><br />So, after all of that, I have a couple of questions that hopefully someone can answer for me. First, is it possible that storing the boat with the gas vent closed and the fuel line connected to the engine (I've never disconnected it) could cause fuel to be forced into the carbs and then into the engine when the tanks get warm and expand? If so, or if for some other reason gas is accumulating in the carbs or fuel system, is it possible the fuel would get past the rings even if they were not heavily worn? Finally, will a compression test give me a reasonable indication if the rings are worn, not properly seated or whatever?<br /><br />I was going to test the compression tonight but found out the compression tester I borrowed does not have the right size threads on any of the adapters. I'm planning on buying a new one to test the engine. If all cylinders seem about the same and decent (not sure what it should be), I will change the oil and filter, start storing it with the fuel line disconnected, and see what happens.<br /><br />Any and all thoughts or answers to my questions would be most appreciated. Sorry for such a long winded post.
