I just read "200 Yamaha won't run right " and I am having a similar problem with my "94 yamaha 85 hp motor . I bought it recently ,had the carbs cleaned ,new carb kits ,new plugs ,electronics checked and general tune up . It idles ok and will turn 5300 rpms at top end smoothly .But it runs rough at 1200 - 2500 rpms when in gear with a load .Once on plane it will smooth out and run fine . I also thought that old gas from the existing built in tank could be the problem so I ran it on a 6 gal tank with new gas . I have checked filters and the fuel water separator 'still the same . Another problem I have is the engine will run at high speed for 15 to 20 minutes and then suck the primer bulb flat . This has happened on both the built in tank and the new remote tank . I installed a tee with ball valves in line at a point prior to the fuel water filter . Running off either tank creates the same problem , but opening both valves to draw from both tanks seems to let enough gas ( or air ) get through . Are these problems related ?
