I have a rebuilt 1997 Johnson 175 HP engine. I used a premix of 25 to 1 ratio for the first 10 hours and never took it above 3500 RPM's. I did do some trolling in the 2.5 MPH to 4 MPH range during the first 10 hours.<br /><br />The engine ran fine the first 10 hours. Pushing a 2,200 lb center console, it was going 25 to 27 MPH at 3,500 RPM's.<br /><br />After 10 hours I cut the oil to gas ratio down to 25 to 1 and put in new plugs. The first time I took her above 3,500 RPM's I heard a rattle noise coming from the engine. When I brought her down to under 3,500 RPM's the noise stopped. I have brought out the boat three times since than and the same thing keeps happening.<br /><br />I now have the engine with the guy who rebuilt it for me. Although it is "out of warrantee" it sounds like he will make good and fix it. He said that if it is anything serious it may take a little time.<br /><br />Does anyone out ther have any idea what it could be?<br /><br />Thanks
