Today, after days of troubleshooting and replacing filters and lines, we finally located the cause of the problem we have with the boatmotor dying at high speeds. The symptoms pointed to the fact that the engine didn’t get enough fuel and actually was able to suck all fuel lines to a vaccuum. The problem is in the tank itself, something is blocking the pipe that is sucking up fuel from the tank. We know this now since everything works perfectly with another tank, but using the same fuel lines. So now we just have to figure out how to solve it, blowing some air into the pipe didn’t help. There is a flow in it, but just not enough I suppose. So while the troubleshooting is now ended, the problem solving part is now under investigation.