Increase in prop diameter?

[clancy72]

Rookie has a few more questions...What effects will increasing from a 14" to a 15" have on a v/p280???? I'm sure it will move more water, but will it strain the drive? I'm currently running a 14"x17p (45mph @4700rpm) 4000# boat medium load (4) and am looking for more top end. I'm thinking 15"x19... It's got a great hole-shot, even with a heavy load.....

 

[Bondo]

Re: Increase in prop diameter?

I'm currently running a 14"x17p (45mph @4700rpm)

Ayuh,.........

You're Already using All the available HP that motor can produce,.....
It's as Loaded as it can Get at 4700rpms......(which is a Perfect place)

If you go Up in both Pitch,+ Diameter,........
Your WOT rpms will Drop,+ you'll be Lugging the motor at All rpms........

If you want to go Faster,......
Be prepared to drop Many Thousand$ of Dollar$,.............


Big Hor$ePower Co$t$ Big Money.........
And you'll probably be needing a Big Block to do it with...............

 

[Boatist]

Re: Increase in prop diameter?

What motor do you have I/O or outboard and what is the manufactor recomended MAX RPMS. If it an I/O rated at 4400 to 4800 then I agree with Bond-O

If it an I/O and your Max Rpms is 4200 to 4600 then I would make the change.
I would look for a 14 by 19 if you can find it. Also for more top end lighten your load. Understand this will lower you Max RPMS by 400 rmps just from the pitch change and the extra diameter will lower it some more. Most you gain is 3 MPH and a little better fuel mileage.

I general I think of larger diameter for slower heavier boats. I think of more pitch for lighter faster boats.

If you do decide to try the change make a deal with the dealer to try the prop but if it does not work out that your can exchange it for something that gets the results you want.

 

[180shabah]

Re: Increase in prop diameter?

This belongs in the prop forum.

 

[clancy72]

Re: Increase in prop diameter?

Enlighten me on how to move it then...

 

[180shabah]

Re: Increase in prop diameter?

You can't, only the mods can.

But I think you will find that when a question is asked in the proper forum you will get the best responses. This is in no way meant to slight the above posts from Bond-O and Boatist, but the guys over in the prop forum really get off talking about bigger ones with a high rake and great lift. There are guys over there who actually test props and have a vast amount of knowledge about what works and what doesn't, but they will never find your question over here, because they don't have sterndrives, they run outboards.

You are missing out on a valuable resource.

 

[clancy72]

Re: Increase in prop diameter?

My bad, didn't notice the prop forum till your comment... Silly newbie anyway..

 

[180shabah]

Re: Increase in prop diameter?

Compared to some of the other Boards(that only have 10 or 12 forums total), iboats can appear fragmented and hard to use at first. Those other boards just don't have the level of experience and expertise that is available here so it can all get lumped together to make it look like there is alot of activity.

Anyway, if nobody moves this thread, you may want to repost in the prop forum, give them as much detail as you can, and see what they suggest.

BTW - thumbnail is too small to tell, is that an old Carlson?? He did some great boats.

 

[clancy72]

Re: Increase in prop diameter?

No, 78' Cobia/Robalo Caribbean.. Chews up big waves when others are heading for the dock..

 

[Firestar]

Re: Increase in prop diameter?

Great looking boat you have there! Your speed and rpm's look just right.

 

[clancy72]

Re: Increase in prop diameter?

Thanks, i've recently been offered a genV 454 on trade.. Do you think the V/P 280 can handle the torque?

 

[f_inscreenname]

Re: Increase in prop diameter?

Thanks, i've recently been offered a genV 454 on trade.. Do you think the V/P 280 can handle the torque?

Another one that needs to read my website. http://www.supernova19.com/motor_build_ii_at_supernova19_com.htm
Just did a 454 to my Frankenstein 270/280 Volvo.

I am also in the same boat so to speak. I can spin a Volvo 15x21 elephant ear, bronze prop around 5200rpm's @WOT. And a Ellison offshore racing prop (14X24) almost 5 grand. I need a 14 X 26+ to get me where my motor should be (4400rpms@WOT). No luck so far.