Switching Gear Ratios
 

It's been a long time and I have a question regarding prop pitch with gear ratio changes.

Last year I was running 32" Bravo 1's to 51-5200 rpms with a 1.50 gear ratio, with about 20% prop slip.

Over the winter I picked up different drives and the gear ratio is 1.30. In addition to changing the prop pitch I am looking to turn higher RPMS (5600) than last year because of where my motors make peak TQ and HP.

I was thinking Bravo 1's with 28" pitch would do the trick? Anyone??

Re: Switching Gear Ratios
 

When going from a 1.5 to a 1.3 you will need to drop the pitch by 10%. That will put you at about 29. If you want to increase your rpm another 400 that's about 2" of less pitch, so that's about a 27.

You are pretty close with the 28's you thought you needed. If you have the 28's they would be a good prop to start with. If you need props to test with give us a call.

Matt

Re: Switching Gear Ratios
 

Thanks Matt! Where are you located, I'm in NJ.

Frank

Re: Switching Gear Ratios
 

Sorry, I forgot to log out and back in on the last post.

We are located in St Pete, FL.

Don't hesitate to call or e mail if you have any questions.

Matt

Re: Switching Gear Ratios
 

Matt, you have two user names?


Panther, the raise in gear ratio (lower #) is about 2 inches in pitch to maintain the same rpm. So dropping yet another 2 inches of pitch in the Bravo 1 propeller family should put you where you want to be. Sounds like you had it figured out already.

Re: Switching Gear Ratios
 

Panther,

I need a set of 32's and I have a set of 28's. Do you want to swap or whatever ?? I went from 1.36 to 1.50 which is the opposite of what you did.

Call me at 847-902-9702 and let me know.


Smitty

Re: Switching Gear Ratios
 

No, visitors occasionally use my computer and don't log out when they are done and I don't check, prior to posting, to see under who's name my computer is logged in under.

Matt

Re: Switching Gear Ratios
 

Smitty,

I'll give you a call. How old are the props, have then been "worked"?

Frank

Re: Switching Gear Ratios
 

Panther,

They are not virgin. I bought them used from a fellow OSO'r. They appear to have been redone at some point. I would rate them a 9.5 out of 10. They worked well for me but since I have changed ratios I need something else. I'll be available tonight by phone.

Dave