My yamaha 20 hp 2 stroke engine will start up ok but when you put the engine under load it will pick the revs up and just cuts out. If you rev it hard out of gear it is fine. If you rev it hard and crash the gears in then it will will keep the revs up but if you back off and then try and speed up again it just cuts out. I hope there is some one out there to help. Many thanks. Marty

Marty, April 2010

I also have the exact same issue with my 20hp Yamaha ... I am thinking it may be a faulty Oil pressure sensor. Did you find the problem?

Smitty, May 2010

The first thing that I would do would be to pull the carby off, strip it down an thoroughly clean it. Remove the main jet and make sure it is clean. Remove the fuel filter and make sure there is no water in the bowl. Clean everything thoroughly. Then reinstall using a new seal ('O' ring) on the carby mounting. Make sure that the air adjustment screw is set correctly. Screw it all the way in until it lightly touches, then screw it out 1.5 turns. See if that makes any differences.

David, May 2010