I have found lots of references to the effect pitch has on performance but nothing on the relationship to prop diameter. What difference could be expected from props 14" x 25P vs 16" x 25P. More or less speed or RPM ?
Thanks
I have found lots of references to the effect pitch has on performance but nothing on the relationship to prop diameter. What difference could be expected from props 14" x 25P vs 16" x 25P. More or less speed or RPM ?
Thanks
rule of thumb for every inch of pitch or diameter = 200 rpm
so going from a 14x25 to a 16x25 will be approx a 400 rpm loss
there are other factors like slip and features like cup and rake that will also effect performance and handling
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What matty said, but w/this caveat;
The reduction in RPM w/the larger diameter probably also means a reduction in slip, so you may actually pick up performance.
George Carter
Central Florida
gcarter763@aol.com
http://kineticocentralfl.com/
“If you have to argue your science by using fraud, your science is not valid"
Professor Ian Plimer, Adilaide and Melbourne Universities
If we're talking specifically about a single engined smaller boat, like ours around here , would I be correct in assuming that a larger diameter prop would also exacerbate the prop torque/lean to port/stbd issue ?
Just because something's old doesn't mean you throw it away !
morgan's cloud yes in general if the same type blade design is used yes
but as george said a larger diameter may have less slip the solas titan is a good example on the volvo aq boats . they have no ill handling traits and have less slip so i did see an overall increase in controlable wot speed
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
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let me clarify my statement
i was running a 14 ish 22 to 26 pitch props on the volvo 16 each had handling quirks the best prop was an ultra 24 but it still got squirely at high speed the ultra was a 14 or 14 1/4 i moved to a 15 5/8 21 pitch solas and picked up a higher controlable top end speed and lost all bad handling traits no ventilation no torque no cavitation or blow out in any water conditions. the solas was not as fast as the ultra but i could not stay at that speed for any length longer than a few seconds.
i had a large 15 something round elephant ear prop it was a pos and torqued the boat badly.
props are like a black science blade design number of blades cup rake labbing all things that have a say in performance
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
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standard rule of thumb is diameter is for accel and torq bite, pitch is for speed and trim
Bad torque issue, try a Left if running a Right hand prop. My boat is a bear with a right. Even broke a steering cable trying to turn at WOT one time. Put a left on it and it drives like power steering. Let go of the wheel at WOT and it goes straight or what ever way I point it.
A winner is just a loser that got up and did it one more time.
1959 Biesemeyer - 4pt Hydro Drag - 2013 ACBS Winner - Best Race Boat
1967 Nova Marine - SuperNova24 - ACBS Winner - 2012 Best Race Boat - 2016 Peoples Choice & Best Non Wood
1972 John Allmand - Nova 19
1972 John Allmand - Nova19 (#2)
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Interesting thread...cleaning up in my garage and found a very nice four blade 14 x 25 Solas prop that I haven't tried yet on my 22C. I have tried a labbed 23P, a Mirage 26p+, and a Mirage 27P, all three blade, with the latter being the best handling...not the fastest, but rock steady at WOT. The 23 is fastest but get really squirrelly and cavitates a lot when accelerating. So, what are thoughts on the 4 blade 14 x 25? I have a new engine going in, a 482 stroker 454 that should be cranking a minimum of 500 hp, and wonder if the four blade might have any advantages. The 27P also holds the RPM under 5,000 rpm which is meaningful to me since I have blown two engines in the past two years
Oledawg
Raconteur, bon vivant, curmudgeon
Other duties as assigned
Lake Tillery, NC - Heart of the Uwharrie Mountains
'88 Donzi Classic 22 "Bad Nuff" - 482 stroker 454, Bravo One, Solas 4 blade, Red/White hull, White Deck ( "drivin" boat )
'87 Correct Craft Riviera "Oledawg" - 454 PCM ( "cruzin" boat )
"A man without a boat is a prisoner" - Faronese proverb
The best all-around prop I ever ran on the Minx was a 15" diameter X 22" pitch Hydro Q-4.
Incredible stability, and NEVER blew out.
I highly reccomend them.
I believe the four blade design and the large diameter were instrumental in its success.
George Carter
Central Florida
gcarter763@aol.com
http://kineticocentralfl.com/
“If you have to argue your science by using fraud, your science is not valid"
Professor Ian Plimer, Adilaide and Melbourne Universities
The larger diameter prop can carry more weight. Small light boats generally perform better with smaller diameter propellers. Heavier vessels require more disk area (diameter and/or # of blades) to carry the weight and keep prop slip numbers in check.
Soooo, what about the 14" x 25P 4 blade? Thoughts?
Oledawg
Raconteur, bon vivant, curmudgeon
Other duties as assigned
Lake Tillery, NC - Heart of the Uwharrie Mountains
'88 Donzi Classic 22 "Bad Nuff" - 482 stroker 454, Bravo One, Solas 4 blade, Red/White hull, White Deck ( "drivin" boat )
'87 Correct Craft Riviera "Oledawg" - 454 PCM ( "cruzin" boat )
"A man without a boat is a prisoner" - Faronese proverb
Thanks for all the helpful information. I had concerns about RPM effect changing from a 14 x 25P Alum to a Solas Titan 21P CR for my volvo drive. Speed was not the most important; control and not over reving was. It was at the suggestion of good people like yourselves that I bought the Solas Prop. Up in Canada it seems very hard to get the solas props as Marinas will order(special) but take several months to get and they can't guarantee you will get it. I ended up ordering from the US. Now all I need to do is wait for the ice to melt in April to try it.
Trevor
the solas is a prop worth having in your arsenal if you have a volvo aq classic. not sure what your power plant is but i was just able with about 310hp to turn a 21 to about 4900-4950 on a 1.6 drive. the size and grip on a solas gives them a point or two above what's stamped on them . a 21 acts like a 22 or 23 .you are going to have to deal with the torque tab if you have a 250 or 270 not a big deal a yammaha ob tab will work the 280 or 290 it's not so much of an issue
When the sky is grey,look out to sea.
When the waves are high and the light is dying,
well raise a glass and think of me...
When I'm home again,
boys, I'll be buying!
My Ride
Come Join Us on The Queen Of American Lakes
Contact Us
www.lgdonziclassic.com
OK, so it sounds like my Solas prop could actually be sort of like my Mirage 27P except that it has 4 blades instead of three, correct? Guess I will bolt the puppy on and check it out
Oledawg
Raconteur, bon vivant, curmudgeon
Other duties as assigned
Lake Tillery, NC - Heart of the Uwharrie Mountains
'88 Donzi Classic 22 "Bad Nuff" - 482 stroker 454, Bravo One, Solas 4 blade, Red/White hull, White Deck ( "drivin" boat )
'87 Correct Craft Riviera "Oledawg" - 454 PCM ( "cruzin" boat )
"A man without a boat is a prisoner" - Faronese proverb
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