your 250 should turn the 27 pitch ok if it turns the 25 easy. the reason I say this is, I bought a new leftover 2006 model 90 hp mercury, it had a 19 pitch on it, and it sounded like it was trying to spin out when I would open the throttle. as soon as I hit plane, I had to back off the throttle because it was turning to higher RPM. a guy I know had a 23 pitch and he let me try it, it was to slow to plane, but would run faster than I wanted to go on top end. just didn't have the power to spin the prop on take off. I tried a 21 pitch and it worked perfect for me. so going up only 2 pitch numbers should work for you. if you can try and find someone with the 27 pitch, that will let you try it before you go and buy one. hope this helps.