Hi guys

My new engine (150 Merc) had a 4 blade prop, but the mech that fitted suggested a 3 blade would be better for the boat (due to weight balance of boat being reasonably forward due to cuddy). 

I currently have the 3 blade 17p off my old motor on it and it was suggested a 15p might be better for fuel economy.  

My limited research says that a 3 blade is preferred for WOT and higher speed, 4 blade for mid range and stability under steam. So I'm wondering what people have experienced in changing one way or the other. WOuld I expect a noticible difference between 3 and 4 blade? And between 17p and 15p? 

Any info would be greatly appreciated. 

Cheers   Mac