Have a Viking 17.0 hp Intek engine had fuel enter sump through faulty carby, problem rectified but now engine won't crank fully. On first attempt it virtually just clicks and won't rotate engine. When I manually turn the engine
One rotation then turn the key it cranks over no problem at all and fires into action. But it does the same thing next attempt to start it. Any thoughts on what could be causing this problem Regards Tony

Sounds like your compression relief isn't working.
Pull the valve cover and check the valve clearance.

There is a video on utube that's pretty good on how to set them.
Tube