Many things. Pipe design, Fuel, glow plug, prop type and setup all can have an affect on how quick you get on to pipe. You need to play with one thing at a time or you will confuse yourself. Start at the pipe length (if you are running a tune pipe). If it is a muffled (canister) motor that would not be one of the things you look at. Next would be prop type and prop height in the water. Higher prop would get revs quicker so the motor gets to tuned revs quiker. smaller prop would give the same affect. It takes time to play with your setup to get it right. Their is no short cut tricks.