Bayliner 2859 7.4 l help with prop selection

[Charles01]

Looking for some prop advice. Size - Pitch for Bravo 2 (2:1 ratio stern drive) Wondering about a larger prop with a higher pitch for better top speed such as 18.8x25? 300 hp to drive it all 454 big block. Currently running an 18x21

 

[Sea Rider]

Need min-max wot rpm range factory stated for that engine.
Max wot rpm achieved as loaded with current installed prop
A 25 pitch will surelly drop too many wot revs as from now with a 21 pitch.

Happy Boating

 

[tpenfield]

Big boat, single engine . . . probably not going to take any more pitch or diameter. I think the 7.4 is doing all that it can do. WOT RPM is supposed to be 4200-4600 RPM. What are you seeing?

 

[Charles01]

4200 RPM seeing 42 kph on differential GPS with our new prop. I did some additional research and discovered the original prop was supposed to be an 18.25x19. So, I purchased an OEM prop and the performance has been much better. However, I am still not getting the expected speed from the boat. I think I should be seeing something over 50 kph. Valves? compression? What next should I try?