How much horsepower to go up a prop size
 

How much horsepower does it take to go up a prop size? Boats is a Schiada RT, has an HP 500, weight 3800lbs dry, prop slip 9.32% according to online, Best Speed 77.4, Spins a 26P, would like to pull a 28 or maybe a labbed 30 but don't know how much more power that would take. Any info would greatly thankful!

going to a labbed 28 would be like spinning a stock 26 but will most likely be faster..what rpm's are you spinning the 26 @ ?

5200, It's really a 28 I had repitched to a 26. I've been told this is makes it really a 26.5.

you will lose 200 to 300 rpm going to a 30 pitch..you will also loose the snappy throttle response in the boat..if your looking for more speed try a 27 p mirage plus with lots of cup..another crazy fast prop is a turbo txp propeller..

Put a - 2 inch imco shorty on, higher x dimension usually you need more pitch

To answer your question. Going up 2 inches in pitch will mathematically gain you 6 mph at the same rpm.
So, the calculated hp increase to gain 6 mph using your current setup as input comes out to be 81 HP.

Hope that answers your question

Bob Lloyd
Full Throttle Marine

Every 1'' of pitch is roughly 150-200RPM, using the same style prop. To gain 100RPM in most cases, requires about 20-25hp.

So, lets say you wanted to spin a 30P prop, to your current rpm of 5200. Right off the bat you will lose around 700RPM bolting the 30p on. That would put you down to around 4500RPM as it sits. Figure 100HP gain, will get you around 4900. 150HP gain, around 5100.

So, it would be like having a 600-625HP engine in that boat, to turn a 30P prop to that 5200 RPM area, which should gain about 10mph, running around 87mph.

Of course there are lots of variables, these are just guidelines.