stillrecon
New member
I have recently purchased a used 90hp Yam 4stroke. The clock says just under 300 hours. After installing the motor and initial start it seemed fine. The next time I started the motor I got a fair bit of blue smoke at start up and it then cleared up. Ran a few gallons through it and it ran fine. Next start up it smoked again. That run was about 5 hours. Started the next day and this time no smoke. Started it again later that afternoon and just a hint of smoke. Relating it to a car engine where the valves are almost upright, where oil can seep into the valve stems/seals, but this is an upright 4 cylinder and the valves appear to be vertically positioned. Going to try and see if it smokes or not after shut down is made with motor trimmed up and then down (like dogs tail). I want to see if that makes a difference. Any ideas? My first thoughts were valve seals/guides but now I'm thinking sticking or even broken oil ring?