I have a Cobalt 190DV and juiced up the engine to about 350hp. I was overreving to 5500 rpm with the 14 1/2" 17P quicksilver prop, I had access to a 15 1/2 19P quicksilver that brought my rpm's to about 5100 which is right where I want to be. My question is...would there be any performance advantage to dropping the size back to a 14 1/2" 21p mirage or quicksilver? I am unsure of how this would effect the overall performance. The boat is a 1979 Cobalt 190DV 21 deg rise and weigh's 2800lbs, I am able to get about 55-56 mph now and am always looking for a little more.

That is a large diameter for a 19' boat. As a rule of thumb increasing pitch 1" slows the motor down 200 rpm. A 19 or 21 mirage plus would work best. I wouldn't expect there to be a big change though.

You could probably go to a 14.5 21 Mirage Plus and piclk up a couple mph.

It has been my experience that smaller diameter with more pitch is generally faster than larger diameter with less pitch.

Chris

I know a guy with a 21 mirage you could try!

thanks for the help, the prop I have is off a bravo drive but gives me incredible acceleration being a 15 1/2 dia. I feel I am limiting my top speed though so I will try a 14 1/2 X 21 Mirage and see if I gain anything...I think the Mirage Plus may give me too much bow lift, as bow lift is not a problem even with a quicksilver prop.