Prop speed?

[Mark]

If you had a gear drive unit fitted to any of the good marine hydro engines what would be the most efficient? Small prop with lots of pitch and cup and geared up for mega revs at the prop or a bigger prop with less revs (reduction gearing)?

 

[lohring]

It depends. A bigger prop will be more efficient and a pitch ratio of around 1.4 to 1.6 times the diameter should be the most efficient as well. However, with the rpm available from current gas and nitro engines, more pitch is needed to break the straight line records. The limit has just about been reached on how much pitch can be added to the existing props. Electric motors are able to turn their props faster and therefore run them with a more efficient pitch ratio. Gears may be the answer for gas and nitro engines. In heat racing the ecisting props work well and there is no need for the complication of gears with surface drive props. Submerged props are another story.

Lohring Miller

 

[DaveMarles]

My experience on a surface drive mono is that reduction gearing is a good improvement. I used a CMB 45 on 1.5:1 gears and 457/3 blade on a 42" mono and had good stability because of the boat size and the speed and acceleration to outrun other .45's that I raced against. Same with the 3.5, I used a 36" long boat with 1.5:1 gears and X450/3 and had better performance than I could have got with a direct drive smaller boat.

Gearing up has had worse performance when I've tried it.

 

[Mike Broad]

I have tried my mono 36" long with a Valvola 21 on both 1:5 and 2:1 reduction and have so far found 1;5 and a x447 3 blade prop to be the best combination. Although I think there is more to come !

The MAC 21 straight drive with an X440 3 in my mono at the moment appears as fast as the geared set up.

Mike Broad

 

[Terry Keeley]

Definately works for me, had two seasons on my little 20 Speedmaster now and am very happy with it.

I run 1.5:1 which Dave suggested when I first set it up. I can rev my NR 21 (7.5" pipe and shorter) higher and still have enough torque out the back not to bog in the corners. I'm also able to race with the hull "wet" and still have good speed. Set up wet for heat racing I can run 45-47mph, with the tabs off and loosened right up I've seen 56 on the Stalker (but 52-54 is more common). I use X450/2, X447/3, and X450/3 depending on the air but the X450/2 seems to be the best.

On my old style direct drive Seaducer (SD1) the best prop was a X440/3, loosened up the hull would hit 50, but it wasn't raceable that way. Tightened up it would do 42ish and bog in the corners etc.

There's a few shots in my gallery:

https://www.intlwaters.com/gallery/index.php?cat=10068

 

[Mark]

Thanks guys, still wondering why it is that the electric guys run mega revs, if a bigger prop and less revs is better or more efficient. When or what circumstances does prop walk become a problem?

 

[DaveMarles]

I'm not an expert on surface drive props but I would guess that those electric motors have torque from 5,000 rpm up to 50,000 rpm, thats the difference, not the prop size.

If you could make a system to effectively vary the pipe length on the nitro motors then that would help but until then...

 

[Terry Keeley]

Dave hit the nail on the head I think, it's more noticable in the smaller motors that have to rev high to get to max power, even then the torque is not that great.

Also I think you can gain some prop efficiency by turning it in the 20K vs 30K range, especially in a "draggy" mono. :blink:

 

[VansRacing]

Terry,

I watched your 20 mono run at the 2004 Nats and it was sweet.

I have a question:

Have you ever seen the geared Thunder Tiger outboard engine run and how did it do in your opinion?

I have been thinking about trying one after I saw your boat this past summer. I think there is something to gain also.

Carl Van Houten,

 

[Terry Keeley]

Terry,
I watched your 20 mono run at the 2004 Nats and it was sweet.

I have a question:

Have you ever seen the geared Thunder Tiger outboard engine run and how did it do in your opinion?

I have been thinking about trying one after I saw your boat this past summer. I think there is something to gain also.

Carl Van Houten,

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Hey Carl:

Nice to meet ya'll in Jackson, that new tunnel is sweet too!

I've never seen the Thunder Tiger but understand they have gears in the lower unit? Also have seen the ratio is only 1.04:1, is that right?

I really think there's an advantage to be had by gearing the 21's, as long as they're set up right and don't rob too much power. Dave mentioned to set the "lash" a little looser than spec for this.

Can you change the gearing on the T.Tiger?

 

[Jerry Wyss]

You can change the gear ratio on the Tigers( OB, of course) if you can find them.

The gear sets that "were" available , 1.19:1 , 1.24:1 , 1.27:1 and 1.46:1.. The two

companies that I buy parts from only have the 1.04:1. If theres anybody out there

that knows the "where-abouts" of these gear sets,,Sing out! (other than 1.04:1)

I'm going to set-up one of my engines with the 1.19:1 gears along with my own

design "head button" and run a X642 prop on a WOF 30 Tunnel. I've ran the 642

on one of my older Tigers with the stock exhaust port timing of 155deg,,it would

get up and go,,but took too long to get there. This time should be Much different

 

[Terry Keeley]

Got a shot of the lower unit and the gears? They should be a stocked item at one of the supply houses. Anybody know what pitch or module (metric) they are?

 

[TimD]

The gearing in the TT works great. I ran the 1.24:1 set in them for years. They also reduce the flex shaft angle in the TT outboard.

I don't have a pic handy but they are not a normal type of gear that you would be able to source elsewhere....

 

[TimD]

Here's the exploded diagram of the TT outboard.

TT Outboard diagram.

Tim

 

[Jerry Wyss]

Hey Tim and Terry, Long ago I remember Jim Irwin and I were conversing over the phone about the TT's,,He mentioned "Boston Gear" about getting a 1:1 set. I didn't follow it up cause I thought at the time that 1.04:1 wasn't that far off that

direction. But now I'm wondering what happened to all those Reduction Gear Sets,

knowing that this engine wasn't All That Popular and that very few buyers would

have Changed the gears anyway. Makes me think that these "gears" might have

been made for a possible another purpose, like a Heavy Duty Spinning Reel or sumthin' like that :blink: Could you imagine , spinning the engine at 33,000 and

1.46:1 gears! The prop would be so Big it wouldn't Fit under the "cavitation plate" :lol:

 

[Nigtmare]

Hey Tim and Terry, Long ago I remember Jim Irwin and I were conversing over the phone about the TT's,,He mentioned "Boston Gear" about getting a 1:1 set. I didn't follow it up cause I thought at the time that 1.04:1 wasn't that far off thatdirection. But now I'm wondering what happened to all those Reduction Gear Sets,

knowing that this engine wasn't All That Popular and that very few buyers would

have Changed the gears anyway. Makes me think that these "gears" might have

been made for a possible another purpose, like a Heavy Duty Spinning Reel or sumthin' like that :blink: Could you imagine , spinning the engine at 33,000 and

1.46:1 gears! The prop would be so Big it wouldn't Fit under the "cavitation plate" :lol:  

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there must be alot of fish out there with there jaw missing :lol: :lol: :lol:

 

[Jerry Wyss]

:lol: :lol: Your More Of A Screwball Than I Am , Nick! :lol: :lol:

I 'magine you could imply alot of torque on a Big Spinning Reel,,I Know I Have.

And have "set the hook" on a "Trout" thinking it was a "Steelhead" and all I ended

up with was the Trouts Upper And Lower Teeth and "Gums" :lol: :huh: Poor Thing

 

[Terry Keeley]

Here's the exploded diagram of the TT outboard.TT Outboard diagram.

Tim

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Now I see the set-up, thought the gears were in the bottom like a full sized O/B. Are they both bevelled or just one? Anything here look close?

http://www.qtcgears.com/

Quite sure they could be found elsewhere, just can't see why a company would go to the expense of making their own gears... :blink:

 

[Terry Keeley]

Hey Tim and Terry, Long ago I remember Jim Irwin and I were conversing over the phone about the TT's,,He mentioned "Boston Gear" about getting a 1:1 set. I didn't follow it up cause I thought at the time that 1.04:1 wasn't that far off thatdirection. But now I'm wondering what happened to all those Reduction Gear Sets,

knowing that this engine wasn't All That Popular and that very few buyers would

have Changed the gears anyway. Makes me think that these "gears" might have

been made for a possible another purpose, like a Heavy Duty Spinning Reel or sumthin' like that :blink: Could you imagine , spinning the engine at 33,000 and

1.46:1 gears! The prop would be so Big it wouldn't Fit under the "cavitation plate" :lol:  

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I have an old Boston Gear catalogue but it's mostly inch series, if this motor was made in Taiwan (is that where TT is made?) chances are they'd be metric. That QTC place in my previous post would be a good bet.

If I was serious into O/B I'd mount a "hot" new motor to that lower unit and take advantage of it!

 

[Nigtmare]

:lol:   :lol: Your More Of A Screwball Than I Am , Nick! :lol:   :lol: I 'magine you could imply alot of torque on a Big Spinning Reel,,I Know I Have.

And have "set the hook" on a "Trout" thinking it was a "Steelhead" and all I ended

up with was the Trouts Upper And Lower Teeth and "Gums" :lol:   :huh: Poor Thing

84866[/snapback]

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Your More Of A Screwball Than I Am , Nick!Nooooooooooooooo way no one is as bad as you are IPMS when I saw that :lol: :lol: I din't know you are a fishing buddy. I have spent alot of time on the rivers for steelhead and brown trout.the bigges steelhead i got was 24.4bl and a 47.1/2 shinook samon.those days are long goen!!!I can't walk more then 500 feet anymore with my back. :angry:about the gear drives.I have two ops 45 g/d that i use on a cat I think they are 1.6:1 ratio. let me tell you i used a 472/3 and a H30/4 props on that thing. the boat looked like it had a 40 Johnson in it :lol: :lol: $h#t man my speling is bad i better stop Nick