Whilst looking at the marine engine i noticed the nut holding the flywheel on was the same thread so i put that on which had enough thread to hold the prop but as i tightend it the engine locked up. Behind the prop flywheel was a plastic washer which was stoping the flywheel going back fully. I took this off put the flywheel and prop on and have now got it started . There did seem to be fuel leaking out from behind the flywheel though?