I have run 3 props: a 25 3 blade a 27 3 blade and a 26 4 blade and I still can only get 68 mph out of my boat. The boat has a 500 hp 600 lb of torque at 4100 rpm's. The only diff is that the 4 blade does not seem to get the nose out of the water as much.

sounds like you have too much pitch. what brand prop are you running? what size/weight boat do you have? you want to turn at least 4800 rpms.

i have a 24p 4 blade hydromotive Q4 for sale if it can work for you.

What rpms are you spinning each prop at??????

Length and weight of boat???????

We need more data. Also check what drive and gear ratio you have.

We need a little more data:

What is your gear ratio?
What is the WOT RPM with each of the props?
What is the MPH with each of the props via gps?

With a little data we can take a look for you.

Julie

All the props reach 5000 rpm's that's the max. the boat is 4900 lb's its 26.5 feet long. The top speed with all props is 68 gps even at 5000 rpm's

68mph at 5000rpm sounds about right spinning a 25pM+ or 26pB1 on your boat.
If you are still able to pull 5000rpm with a 27pM+ then you should be going faster than with a 25p.
What size engine?
454s normally make 500HP at about 5600rpm and 502s around 5200rpm.

The engine is a 565 ci. I was expecting 75-80 on this hull.

[QUOTE=perform330;2096127]The engine is a 565 ci. I was expecting 75-80 on this hull.

Post the dyno numbers for hp and torque from 3500-6000rpms.