Prop size

[Zinger11]

Will going from a 15x15 to a 16x16 increase my rpms at wot

And if so how much

Thanks

 

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[Bozeman Bob]

You are going the wrong way. That pitch will decrease your RPMs by a couple hundred. Every inch of pitch equals about 200 rpm up or down , in your case I would guess with the bigger diameter and pitch you would lose 300 +rpms The bigger the diameter the slower it will go over a stock unit. In most cases bigger diameter props are for semi displacement hulls. What RPMs are you running and what is the motors advertised maximum rom range ?

Edited August 13, 2017 by Bozeman Bob

[Zinger11]

You are going the wrong way. That pitch will decrease your RPMs by a couple hundred. Every inch of pitch equals about 200 rpm up or down , in your case I would guess with the bigger diameter and pitch you would lose 300 +rpms The bigger the diameter the slower it will go over a stock unit. In most cases bigger diameter props are for semi displacement hulls. What RPMs are you running and what is the motors advertised maximum rom range ?

I have a 25 footer just put a new 5.7 and I can't get the rpms over 3000 underway but in neutral 3,000 RPMs is like a throttle

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[Bozeman Bob]

So this a new power plant of the same cubic inch or has that changed. Straight Inboard ?  Really shouldn't rev her up to 3gs in neutral. I would assume you have had it timed as well.

Edited August 13, 2017 by Bozeman Bob

[Zinger11]

When I bought the boat it had a 16x16 on it and i was given a 15x15 that I changed so i never ran the 16.

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[Bozeman Bob]

I am going to assume its a inboard and the same cubic inch engine and it has been timed as well since you didn't answer my questions. Just cant see going any less than 15" in pitch on a boat that size . I am leaning towards something engine related like the carb not opening up all the way. Have you checked the linkage vs the movement of the carb linkage ? Really need more specific info

[Zinger11]

Thanks Bob for the help my static timing is 10 degrees bdc center and my original motor was 260 hp I replaced it with a 330 hp with a brand new carburetor which is opening up all the way

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[Bozeman Bob]

 Let L+M talk you through it. Just trying to.help seeing that no one else was offering any suggestions ,help,thoughts on what might be the issue.   

Edited August 15, 2017 by Bozeman Bob

[L&M]

PM sent Zinger