It is fixed thanks to you all and my md7a is the happiest now!
It was the clogged tank sucking line! :s
I made a plan based on these comments and went on board today. As Whatfiero1 said, went inside the small hatch on the port side and took the suction line out from the tank.
Here is the video;
Looking for all kind of suggestions except throw this old engine away as i love my old friend and so far he was so reliable
When i start the engine it runs like a normal (idle) then rpm increasing and normal up and normal, then it goes up and at certain...