do i have the right prop?

[Weruehl]

I do have a 05 191fs with a 150 hp.mercury optimax saltwater. The boat runs great. With a full tank of gas two people and trimmed out the engine turns 5000 rpm .max at 50 mph. The prop is alu. 14.5x21 pitch. The book says the engine should turne 55 to 5800 rpm. I have changed the prop to 14.5 to19 pitch. The result , the motor still runs at 5000 rpm max. but dropped speed to 45 mph. I would like to bay SS prop. How do i increase the rpm and what sice prop should i bay ?

[Cincinnati]

I'm surprised that your RPM didn't increase but not surprised that your speed dropped by reducing the pitch by 2". Have you tried a smaller diameter? I run a 13.25X17 on my 130HP pushing my 190 Bay, but normally don't get much above 40 mph and 5500 rpm. I've not gone up in diam or pitch as slow trolling is more important for me than getting to the next spot in 10 seconds.