yamaha 70 eng

i have 2005 yamaha eng 70 hp .some time cut off at full thr.... need help.well make that all the time.and wend i get going it has no power.what du i need to do.

I would start with checking the coils and wires and replacing the spark plugs. Bad/old plugs will cause engine to run on 2 cylinders instead of 3, resulting in under powered running. If plugs are new, this problem and the shutting off/cutting out at high rpm could be a bad coil. A weak coil will often work when cold but as it heats up it breaks down and no spark on that cylinder. Of course, your entire problem could be carburetors, but start with the spark first. Need more info.