Hydromotive first run

[whipper]

I was hoping we was finished with this BUT, My Hydromotive O/T's do have trailing edge cup, Todd knows his prop better than anyone so I'm just taking him for his word.

For 17 years of myself being in the Propeller business I have always added 1 pitch for cup. Theres no misunderstanding of propellers on my part.

Hears a Q for you Jay somthing ive wondered about. Tow props measure same pitch exactly ones a 4 blade ones a 3 blade. If the 4 blade runs the rpm as the 3 blade witch will be faster. I was always under the imprestion the 4 blade would be at the same rpm. Never really tryed that before. I know theres a rule that some use to apply to 4 blades that you loose some rpm with a 4 blade. So if you could use that to match the 3 blades rpm would that gain you speed in a 4 blade? Also another thing about Slip.:help Is the formula the same for a 3blade as a 4 or 5 blade prop in the calculation?

Pretty interesting thread if ya ask me. ive learned lots. I think the biggest thread is the Darris says no to 300 on a GS though?:big grin OR the one about a 24ft Grand Sport doeing close to 90 with a stock 225 promax and a 27 trophy.:big grin

 

[xb03]

I believe that there are to many variables in different props, hulls, weights, aerodynamics, and all the small thing that we do to get 1 mph here and there (without changing pitch, gears, or rpms). For the prop slip calculator to be that accurate. Just my opinion.

 

[SLOmofo]

This is all a moot point when your second to the finish line! :big grin

4 blade is usually smaller in diameter there for the engine height might have to be lower, gear case drag= slower.

Get your ticket yet? :beer:

 

[whipper]

This is all a moot point when your second to the finish line! :big grin

4 blade is usually smaller in diameter there for the engine height might have to be lower, gear case drag= slower.

Get your ticket yet? :beer:

Todd said this one was 14.75 dia = higher. :big grin

And my wife is a Manager for Air Canada so yes I can get a ticket.

Only if you take me for a ride in your boat.

 

[Jay Martin]

Hears a Q for you Jay somthing ive wondered about. Tow props measure same pitch exactly ones a 4 blade ones a 3 blade. If the 4 blade runs the rpm as the 3 blade witch will be faster. I was always under the imprestion the 4 blade would be at the same rpm. Never really tryed that before. I know theres a rule that some use to apply to 4 blades that you loose some rpm with a 4 blade. So if you could use that to match the 3 blades rpm would that gain you speed in a 4 blade? Also another thing about Slip.:help Is the formula the same for a 3blade as a 4 or 5 blade prop in the calculation?

Pretty interesting thread if ya ask me. ive learned lots. I think the biggest thread is the Darris says no to 300 on a GS though?:big grin OR the one about a 24ft Grand Sport doeing close to 90 with a stock 225 promax and a 27 trophy.:big grin

Whipper, As far as I know there is only one calculation for prop slip. Yes when going from a 3 to a 4 blade rule of thumb is to drop 1 pitch. theres a lot to consider on this subject like diameter, most 4 blades drop in diameter vs. a 3 blade like the Trophy thats a 13 3/4 or the Turbo TXP thats 14 3/8. Pitch can be replaced by diameter and a prop that has alot of cup can replace pitch, adding cup to the trailing edge is the same as adding pitch, it will also lift your stern.

I've always been a firm believer that a 4 blade is the better prop for extreme surface running, the more blades the better it holds. To answer your question about will a 4 blade as fast as 3 blade, I say yes it's possiable, especially with Todds props, Why? because of the amount of blade area his prop has along with lab finishing.


Tow props are normally what we call "straight pitch" meaning from the leading edge to the trailing edge the pitch is the same. What we run are called "progressive pitch" like Todd explained earlyer. You are correct about 3 vs. 4 blade, on our style of boats (Allisons) a 3 blade will be the faster prop but for handling purposes most of us prefer the 4 blade. I know I do.
Now, on heavy boats or boats that are carrying a heavy load like a big Ranger a 4 blade will be the faster prop because of it's weight carrying ability, of course over time this has also changed, Yamaha has a 3 blade called the T-1, it's a 15 1/8 diameter, this is a fast prop that will carry the weight like a 4 blade, it's blades are huge.

One thing I have learned since being an Allison owner and being on this site is Allison owners are different meaning an average Joe running a Triton or Ranger just wants his prop to run. An Allison owner wants his boat to run with a full detail of how and why it's doing what it does....I guess I'm in the right place cause I'm the same way...

 

[fnshrmaster]

This has been a very informative thread, this being my first Allison I have learned much from this forum. Thanks! Kurt

 

[TBuck2003]

I was hoping we was finished with this BUT, My Hydromotive O/T's do have trailing edge cup, Todd knows his prop better than anyone so I'm just taking him for his word.

For 17 years of myself being in the Propeller business I have always added 1 pitch for cup. Theres no misunderstanding of propellers on my part.

Jay,
Yes they do have a slight bit of traling edge cup, but nowhere near what the others do. The point of adding 1" to every prop does not work for every (MY) prop. Ask yourself what part of the blade is doing the work at high speed, vs. what part of the blade is doing the work at cruise???? Remember we are talking about surfacing vs. submerged, a different ball game completely. It is a new deal compared to a Triton that is 14ft. beneath the bottom of the boat...lol That was a joke... Great input from all on this thread, now go to church, and pray for summertime!!!!!!!!!!

TBuck

 

[catfish123]

I've been praying for it even though we have had a relatively mild winter! I can't wait to get back up to the lake.

 

[Jay Martin]

Jay,
Yes they do have a slight bit of traling edge cup, but nowhere near what the others do. The point of adding 1" to every prop does not work for every (MY) prop. Ask yourself what part of the blade is doing the work at high speed, vs. what part of the blade is doing the work at cruise???? Remember we are talking about surfacing vs. submerged, a different ball game completely. It is a new deal compared to a Triton that is 14ft. beneath the bottom of the boat...lol That was a joke... Great input from all on this thread, now go to church, and pray for summertime!!!!!!!!!!

TBuck

Todd, I could not agree with you more, I was trying to make an example of heavy vs. lite so that everyone would have a better understanding of the subject....:at the bar.....

 

[Lotus 50]

With a progressive pitch prop, who other than the manufacturer knows where the pitch is measured? In theory, you need slip to get forward motion. 30 years ago I could have done the math to prove this.

I get calculated negative slip sometimes with my SS. Either my tach reads a bit low (most likely) or the props run at the high side of the progressive pitch.

 

[whipper]

Interesting Lotus. Your point is good because your setup is very, well pretty unique in that you have a very light hull in a SS have a light 150 hp motor and run 30 pitch 4bld props. Im not even going there exept that to run high 80,s to 90 which I think i remember you do with your setup with a 30 your slip numbers would be low. Also the T4-X 30 prop youve run is known to run very high speeds with less rpm at high prop shaft hights. On your light low HP setup your sure not going to need as much thrust to get the same speeds as say a XB03 with more HP or that and heavier hull would.

It also could be said that the lighter the hull the less the slip number. The efficiancy of your setup would be real high I would emagine.

 

[SLOmofo]

Todd said this one was 14.75 dia = higher. :big grin

And my wife is a Manager for Air Canada so yes I can get a ticket.

Only if you take me for a ride in your boat.

"Yamaha has a 3 blade called the T-1, it's a 15 1/8 diameter, this is a fast prop that will carry the weight like a 4 blade, it's blades are huge."

This is very interesting who has these? What pitches do they come in? I need something that will hold up for lake usage, there are no drag races any where near where I live in Ca. Last year alone I broke a 22" and a 24" prop.
Todd has a 26" chopper I had sent to him to make into a Knob cut he'll be working his magic on soon.

James, right now the engine is getting a make over plus a couple of new tweaks. I don't hold my breath as these can take a long time depending on Dave's actual work and other engine projects.

Of course I'll take you for a ride. Might have to install oar locks though. :laughing

 

[whipper]

Of course I'll take you for a ride. Might have to install oar locks though. :laughing

Ill row. Maybe drag a dry fly while im at it. Nothing works better than rowing a fly on the surface in the spring.:beer:

 

[Jay Martin]

"Yamaha has a 3 blade called the T-1, it's a 15 1/8 diameter, this is a fast prop that will carry the weight like a 4 blade, it's blades are huge."

This is very interesting who has these? What pitches do they come in? I need something that will hold up for lake usage, there are no drag races any where near where I live in Ca. Last year alone I broke a 22" and a 24" prop.
Todd has a 26" chopper I had sent to him to make into a Knob cut he'll be working his magic on soon.

James, right now the engine is getting a make over plus a couple of new tweaks. I don't hold my breath as these can take a long time depending on Dave's actual work and other engine projects.

Of course I'll take you for a ride. Might have to install oar locks though. :laughing

Yamaha dealers carry these props but I wouldn't suggest it on an Allison, you might flip over with as much lift this prop has. It was designed for 225-250 horse on heavy boats, Rangers, big Skeeter etc. Only other boat I've seen this prop used on thats anywhere close to an Ally (which it's not) is a Blazer.
It's a big barell prop with 3/4 inch exaust relief holes for holeshot, it only comes with press in rubber hub which is standard 15 spline but can be ran on a merc. I think they go all the way to 29 pitch, most popular are 25's and 27's.

 

[SLOmofo]

Yamaha dealers carry these props but I wouldn't suggest it on an Allison, you might flip over with as much lift this prop has. It was designed for 225-250 horse on heavy boats, Rangers, big Skeeter etc. Only other boat I've seen this prop used on thats anywhere close to an Ally (which it's not) is a Blazer.
It's a big barell prop with 3/4 inch exaust relief holes for holeshot, it only comes with press in rubber hub which is standard 15 spline but can be ran on a merc. I think they go all the way to 29 pitch, most popular are 25's and 27's.

Soooo, a 21" or a 23", 450ish HP on a XB2003 with a Heavy Weight OMC.
I'll talk Bill Smith into being the "Test Dummy", I'm sure he has plenty of insurance!

 

[Jay Martin]

23 is the smallest they come in...Keep me posted on this if you do it....
This prop has alot of parobolic rake.

 

[xb03]

Heres a video from that day before I raised the jackplate to 1/4 above, running 90.5 mph. I want yall to watch the tach, because it stays on 6750 for a few seconds but then jumps around.

 

[Jay Martin]

Maybe it was trying to jump up to where it wanted to be, could be reading low, I would find someone that you can borrow a tach from to compare, leave yours connected and run a pigtail from your present tach to the borrowed one, have your buddy hold it while running and compare the difference.

I had a EGT guage acting stupid 2 months ago, it kept bouncing up to 1200 degree's, scared me stupid, I thought for sure I was getting ready to replace a piston. I could tap on the guage really hard and it would settle back down for a moment, I replaced it and all's well again.

 

[2003225X]

xb03:

I would definitely run a seperate wire if you can and get an accurate tach reading.

My dad was having a lot of issues getting his tach to read right, and it ended up being a ground.

Just an opinion, but that motor sounds like it is turning more than 6750.

 

[xb03]

The tach works fine untill I go wot, then it starts jumping, the only thing I've done so far was swap my tach wire to the port side voltage regulator, and it does the same thing. Thanks, for the comments I'll try any ideas to get it working correctly.