I have a 1998 7.4 mercruiser Bravo1 long story short I'm installing a new raw water pump and can't figure what way the impeller fins need to go. Not sure what rotation my engine is either and serial # is worn off... Any help would be so appreciated

With the plastic housing in your left hand. Twist the impeller into the housing clockwise. put the impeller on the shaft of the belt pulley, soap it up and twist in holding on to the belt pulley

Crank the motor over with the starter the should give you a good idea.

That's not possible Right now

Standard engine is left hand as viewed from the flywheel end..

Typical engine is left hand rotation. Look at the rear of the impeller housing. It will show the direction of rotation for both left hand and right hand rotations.
Eddie

won't really matter, when you spin it over will go to right direction, make sure you lube well, and make sure you don't cross the hoses, that makes big difference..