water rapper

I recently installed a 575 sci with the XR drive into a vintage 25 foot Corsair. Previous to this power upgrade, the boat ran mid 70's with a 425HP big block and bravo 1. The boat weighs 4850 lbs with 70 gallons of fuel.

Here is is issue... the motor under load does go over 4200 RPM. With a 28 pitch prop and a 26 pitch prop produced to the same result of 4200 RPM - just different speeds. The 28 pitch at 4200 RPM ran the boat to about 72 MPH. We threw on a 23 pitch and the boat ran up to the rev limiter. Even with the 28 pitch prop at 4200 RPM, the motor does not appear to be laboring or running out of power. At 4200 RPM, the boost is reading about 4 lbs.

We tested the fuel system, we even ran dual 1/2 inch fuel lines to ensure a sufficient fuel supply. We ensured there was sufficient air supply by taking the engine hatch off. We also checked to see if the knock sensor was triggered. It was not.

Any guidance on this one???

Thanks, Ed

bidell911

I have been helping my uncle "polish" his 88' Corsair 25 (replace broken gauges, compound and wax, repair seat cushions, repaint the outdrive, touch-up bottom paint, etc.). The boat is in good condition overall , though. We will be posting a website later this summer at www.corsairpowerboats.com and will be updating www.corsairpowerboats.blogspot.com. The purpose of these sites is to provide a forum for owners of Corsair Powerboats to share information and ask questions. We have a bunch of original Corsair documentation that we will be posting on the website to help people learn more. In the meantime, if you own one of these boats, have information about these boats, or need information about these boats, please feel free to email me at [email protected].