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Why aren't variable pitch props for regular boats more popular?

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  • 1 Post By tugtrash

Why aren't variable pitch props for regular boats more popular?

Old 05-11-2018, 07:22 PM
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Default Why aren't variable pitch props for regular boats more popular?

I was watching a show about aviation and one of the biggest advancements in propeller driven planes was a variable pitch propeller. I know that they are made for some container ships and cruise ships but if someone made one that was affordable to regular boater/fisherman I think it would be a huge seller. Even more so when fuel efficiency is more and more of a concern? I saw some on the market but they can't be adjusted while underway, lowering the pitch to get up on plane and then increasing the pitch after on plane would be great. Same concept as transmissions in vehicles.

Last edited by RussH; 05-11-2018 at 08:39 PM.
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Old 05-11-2018, 07:24 PM
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I have thought about that too. I wonder about the affordability issue.
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Old 05-11-2018, 07:26 PM
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I would assume more moving parts means more stuff to break.
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Old 05-11-2018, 07:28 PM
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Do a search...it's been discussed here before.
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Old 05-11-2018, 07:40 PM
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Land & Sea made one back in the late 80’s- early 90’s seems like was called TorqueShift. Used cams, springs, and centrifugal force to shift from lower to higher pitch. I think with newer design and manufacturing techniques a better mousetrap could be made.
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Old 05-11-2018, 08:25 PM
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I had a variable pitch prop on my old 35 HP Evinrude many decades ago but it was manually adjustable and not very efficient compared with regular ones.
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Old 05-11-2018, 08:44 PM
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Originally Posted by fly186 View Post
Do a search...it's been discussed here before.
Before I posted this I did do a search on "variable pitch" and didn't get a single find. I even did an advanced search and nothing came up.
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Old 05-11-2018, 09:11 PM
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This is one of the threads I remember. Variable pitch is discussed starting about 1/2 way through:
New Propeller Innovation: Looking for Comment and Interested Parties
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Old 05-12-2018, 12:05 AM
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Torque

One thing why they don't is the torque. I like hole-shot.. Our lowers are tough but just like changing gears in a car, when you run a lower gear you put more stress on the moving components and the ass end of the boat. .
Simple math. I moved from a 4.11 rear end gear to the 4.56 cause I only run 1/8th mile all the time. Picked up a 10th of a second. Does not seem a lot but when your already in the 4.8 second range and 150 mph a 10th by rule of thumb is 100 HP. Its putting more stress on everything from transmission to rear end.
On one of my older bass boats I run a 23 pitch. Didn't have a ski boat the bass boat had to do it. I'd drop back to the 19 pitch I could pull two skiers. Ended up blower the lower with it to.

With the Fountain with the twin 225s on it I was at Fountain. They did some work on the motors told me it was ready they dropped it on the water the guy from fountain was driving , BAM.. Blew a lower. Under warranty they fixed it right there. Mercury sent me a new lower.

Also the transoms have to be built for that much torque. Jack plates I think could handle it but the race boats use shaft not props.

Something to with the gap in the blades for moving it would greatly affect your top end performance. When you send a prop in to have it set to max proformance, they lab it where the water flows the easiest around the blades. My Allison BB I had would run 98. 2.5 worked,,,, talk about feeling a difference just one change could either make or brake a prop. I've sent a prop end to get the other edges knifed. Picked up 2 mph.


Lot more cost in designing the boats and lowers then come in a stock motor. My pontoon max on that is 115. Which sucks. LOL I'm leaving the 50 hp on it till it blows then moving up to a 150. If it falls of the back at least its not going to hit us in the pontoon. LMAO.

I run a modded 25P 4 blade bravo rear lifter on my boat. I can turn a 27 three blade. 74 mph is tops with the three on my TR21x Triton.
67 is tops with the 4 but its a rocket ship on rails coming out the hole and I don't cruse but 48 to 50. Like most Bass boats we fish in a lot of shallow water. You have two choices. Speed props you have to idle out so far to take off. Mine, I can kill it in 3 foot of water and its on plane in about 2.5 seconds. Back of that bass boat is built for high HP motors. Lot of boats are not. Torque has to be thrown in the mix as a factor anyway.
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Old 05-12-2018, 01:23 AM
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A ship I worked on in the Great Lakes had a CPP unit. The 2 main engines were constant speed 750 RPM into a single reduction gear with shaft generators out of the back of the gears. One of the main advantages is effeciency being able to run a pair of 2000 KW gensets that doesn’t really translate to the pleasure boats. Also the hydraulics for the pitch control run down the length of the shaft and probably wouldn’t be the cheapest thing to maintain on an average boat.
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Old 05-12-2018, 02:35 AM
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Cost. Too complicated. Too slow to respond on fast boats
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