prop needed on active thunder
 

have a 25 active thunder with 454mag carb motor.turns 23 mirage at 5100 rpm and 67 mph with 1.36 b1.switch to 25 and only pulls 4400-4500 at 63 mph.the front of the boat bounces like crazy.should i switch to four blade?maybe a labbed 23 four blade

Re: prop needed on active thunder
 

I think you will appreciate the performance of a 4B propeller. It really should calm down the porpoising issue. I would recommned starting with a 22P Stock Bravo I and baseline the propeller. If it runs at around 5000 RPM then you could consider lab finishing a 24P Bravo I.

Julie

Re: prop needed on active thunder
 

julie will this cost me any top end?do you still do that testing program?

Re: prop needed on active thunder
 

Yes, it is possible to loose 1.5-2 MPH going from a 3B to a 4B but this is really dependant on how well your 3B props is dialed in.

Julie

Re: prop needed on active thunder
 

Having quite a bit of experience with the 25 Active Thunder, I would highly recomend either trading your Bravo 1 drive to a drive that has a 1.50 gear ratio, or check cost on simply changing gears in your existing drive.
Once you have a 1.50 drive, then get with Julie and look into a 22p 0r 24p bravo-1 4 blade props, (the 25 Thunder loves bow lift). Find the prop that will get close to 4850-4900rpm and send it back to Julie to be Lab-finished. You will be very happy with the results.

Re: prop needed on active thunder
 

gordo can i keep my 1.36 and just prop to 4900.what is the advantage to switch to 1.50?i run 5100 now 454mag carb is this the correct rpm

Re: prop needed on active thunder
 

I believe Gordo is suggesting the throttle response you will get by going to the lower gear ratio. Even though the prop will be bigger the boat will respond quicker.

The 4 blade may actually increase the porpoise issue. That problem can however, be dialed out of the prop.

Re: prop needed on active thunder
 

I would listen to Gordo he is the man on those 35 ATs