Helge,

I must ask first if your engine was new when you received it? If so, it may take a bit of running to settle in. There are many threads on running motors in. Once done the compression should hold better and produce more power.

For fuel, I'd recommend the Oliver brew, 20% Castor Oil, 30% Ether & 50% Kero. to that you can add whatever amount of ignition improver is dictated by local conditions. If, like many others around the world, you have trouble sourcing the required fuel components, look to local clubs where diesels are being used.

I wouldn't recommend that you keep using that old prop. There have been many cases of blowing blades off those. Modern props are much safer.

Like the others, I'd recommend either the Peacemaker, or the Blue Pants.

Good Luck

Greg