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-   -   Propeller change with HP change? (https://www.offshoreonly.com/forums/prop-talk/342778-propeller-change-hp-change.html)

Tahoe540 11-20-2016 05:58 PM

Propeller change with HP change?
 
Boat is a 30ft Advantage offshore single currently running a hc-cl 24r Q-IV Hydromotive prop (14.75 diameter) for Lake Tahoe and I also have another prop for sea level ( it is the same prop but different pitch and don't know offhand). This is a new boat to me and I will be installing a motor that is approximately 200-250 HP more than the old engine. I will be using the prop I have but is there anything I should be looking for that may indicate a different prop is needed?
http://i393.photobucket.com/albums/p...psurxk2wox.jpg

class6 11-20-2016 06:12 PM

Banging off the rev limiter

Mr Maine 11-20-2016 07:24 PM

What is the rpms difference at max power for both motors?

Tinkerer 11-20-2016 07:41 PM

The higher HP engine usually has a higher RPM range so you may be able to run the same prop.
I was spinning a bone stock Bravo 28 at 6000 RPM with the 650 HP engine with a 1.5 to 1 ratio drive.
I am now spinning the same prop at 6100 RPM with a 800+ HP engine with a 1.34 to 1 ratio drive.
I bought a BBlades labbed Bravo 28 this fall hoping to try it out but it never happened.
I hope this gets me to 6400 RPM and with the added cup to help getting on plane and less trim.
I have to trim to 7 to 7.5 now ( neutral is 5 ) for top speed. Brett thinks this new prop should help keep the trim down to 5.5 to 6 instead.
I can't wait for spring.

Tahoe540 11-20-2016 07:43 PM


Originally Posted by Mr Maine (Post 4502682)
What is the rpms difference at max power for both motors?

This is where my issue lies as I got the boat without the motor installed and have no real information other than top speed on Lake Tahoe with the previous motor. The new motor should be in the 5500-6000 rpm range and approx 600 HP.


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