Jo. Jason mentioned using a flywheel instead of a prop for running your engines and he has got a point, I ran a ED Racer, ED Sea Otter, and a 15cc Gannet OHV when I was into model boats all started and ran no bother.
With test bed running you could use a electric starter and not be bothered with a starting cord, the only thing would maybe be a cooling issue but worth a try.
Mike.