Prop question, and results from my spun prop.

Big-E

Petty Officer 2nd Class
Joined
May 2, 2005
Messages
135
Last weekend i spun the hub on my prop so i took it to prop place. I have a 3.0 L GM 4 cyl I/O in my 17 foot bowrider. 1st off they told me my prop was not worth reparing and was a huge 15 x 23. But its diamitor was worn down to the dia of a 14 " blade.<br /><br />Thats the history, my question is what size prop should i run? He thinks a 15 x 17 would be perfect. My rpm range is 4400-4800 rpms for the motor and with the old worn prop was only 4100 rpms. This kinda complicates things since the diamitor was only 14" not 15" what the prop used to be. To make mattesr a wee bit more interesting i want to get a 4 blade..<br /><br />Thanks,<br /><br />Big-E
 

Big-E

Petty Officer 2nd Class
Joined
May 2, 2005
Messages
135
Re: Prop question, and results from my spun prop.

update!!
 

TilliamWe

Banned
Joined
Dec 21, 2004
Messages
6,579
Re: Prop question, and results from my spun prop.

If you don't have access to Trailer Boats Magazine July 2005 edition, I'll summarize it for you.<br /><br />1" decrease in pitch should raise WOT rpms by 100 to 200.<br />Going from 3 blade to 4 blade of same pitch should drop WOT rpm by 100 to 200.<br /><br />Can you do the math from there?<br /><br />Don;t worry about diameter so much, you will have very little choice. Most manufaturers only make props of a certain pitch in one diameter.
 

Big-E

Petty Officer 2nd Class
Joined
May 2, 2005
Messages
135
Re: Prop question, and results from my spun prop.

Yea i can thanks. I'm thinking then a 15 x 19 would be right.. But the diameter would have been my 2nd question as i have seen most in 14 1/4 and not a full 15. Right now im going to get a used 19 pitch and see how that does for WOT .. SHould bring me right up to 4800 or just below.. <br /><br />thanks, <br /><br />Big-E
 

TilliamWe

Banned
Joined
Dec 21, 2004
Messages
6,579
Re: Prop question, and results from my spun prop.

Yeah a 19 pitch 4 blade should put you right at the top of your rpm range. Don't be totally surprised if you end up a little over. <br />Just remember, you should test this replacement prop with the normal load that the boat will carry. So if you normally have 8 people aboard & coolers & full of gas, test it that way.
 
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