Hustler performance vs Tohatsu prop. ???

[towtruck1]

I recently tested the TP Hustler 10.75 x 12 I ordered. My expectations were that I would get to the top of my RPM range and lose just a bit of speed. According to my calculations, I should have seen about a 4 mph drop given the increased rpm (assuming identical propeller design), but I was expecting the difference to be a bit less due to TP's high-performance claims, and what I had been reading. Here is what I got:


All numbers at WOT, identical trim, identical boat weight (estimated at 1100 lbs all up). Both props tested w/in 5 min of each other.

6-yr-old Tohatsu Al prop (11 x 13.5):
5400 rpm, ~34.5 mph INDICATED

New Hustler 10.75 x 12:
5650 rpm, ~25.5 mph INDICATED


Can anybody explain how such a highly touted prop could do so poorly? I understand the speedo might not be perfectly calibrated, but I sure didn't expect to see this kind of speed loss!

I talked to someone at TP, and he talked to his engineer and wanted me to move to the 10.375 x 15 to get about the same speed as my old Tohatsu prop. When I mentioned that I also needed to get a skier out of the water, he was stumped (The Tohatsu 11 x 13.5 pulls me out consistently on a single ski, but it takes a few seconds). He also told me that "some propellers just don't work on some boat/engine combinations." Very encouraging.

At this point, I'd be happy just to have a replacement prop that gives me the same performance as my old prop. I can exchange for a small fee, but don't want to got through this excercise more than I have to. Any thoughts regarding the HUSTLER?

Also...
Tohatsu doesn't have the 13.5 available anymore. I'm assuming the basic design hasn't changed. I'd like the same or better speed (14P), but am concerned a 14P won't pull me up anymore. Any thoughts on whether the extra half pitch will make much difference in that department? I don't mind if it takes even longer, as long as it gets the job done.

Thanks for all your thoughts. They are appreciated!

Towtruck

 

[Tail_Gunner]

Re: Hustler performance vs Tohatsu prop. ???

I recently tested the TP Hustler 10.75 x 12 I ordered. My expectations were that I would get to the top of my RPM range and lose just a bit of speed. According to my calculations, I should have seen about a 4 mph drop given the increased rpm (assuming identical propeller design), but I was expecting the difference to be a bit less due to TP's high-performance claims, and what I had been reading. Here is what I got:


All numbers at WOT, identical trim, identical boat weight (estimated at 1100 lbs all up). Both props tested w/in 5 min of each other.

6-yr-old Tohatsu Al prop (11 x 13.5):
5400 rpm, ~34.5 mph INDICATED

New Hustler 10.75 x 12:
5650 rpm, ~25.5 mph INDICATED


Can anybody explain how such a highly touted prop could do so poorly? I understand the speedo might not be perfectly calibrated, but I sure didn't expect to see this kind of speed loss!

I talked to someone at TP, and he talked to his engineer and wanted me to move to the 10.375 x 15 to get about the same speed as my old Tohatsu prop. When I mentioned that I also needed to get a skier out of the water, he was stumped (The Tohatsu 11 x 13.5 pulls me out consistently on a single ski, but it takes a few seconds). He also told me that "some propellers just don't work on some boat/engine combinations." Very encouraging.

At this point, I'd be happy just to have a replacement prop that gives me the same performance as my old prop. I can exchange for a small fee, but don't want to got through this excercise more than I have to. Any thoughts regarding the HUSTLER?

Also...
Tohatsu doesn't have the 13.5 available anymore. I'm assuming the basic design hasn't changed. I'd like the same or better speed (14P), but am concerned a 14P won't pull me up anymore. Any thoughts on whether the extra half pitch will make much difference in that department? I don't mind if it takes even longer, as long as it gets the job done.

Thanks for all your thoughts. They are appreciated!

Towtruck

http://forums.iboats.com/showthread.php?t=268219

It started here and will give more histroy

 

[towtruck1]

Re: Hustler performance vs Tohatsu prop. ???

TailGunner

Thanks for your contribution! The data demonstrates that the (12x10.5) is way off. I've got the RPM I wanted (which you suggested I could only get with your prop); I just don't have the speed I expect. If anything, a lower pitch is going to lose me even more speed.

I talked to an engineer yesterday and learned a few things:

1) I was wrong to assume I would necessarily get more power by going to the top of my RPM range. 2-stroke engines have a 'peaky' power curve due to the way they are aspirated. In general the power curve may (will usually) peak somewhere before the max RPM, and then fall off, perhaps substantially. I don't know the characteristics of my engine, but it is likely I was already right at the top of the power curve with the old prop.

2) All the talk I have heard here about "don't worry about diameter" is way off. True, diameter doesn't come into the speed vs. pitch equation, but it does come into the RPM equation. RPM is a function of pitch AND diameter. The trick is finding the best COMBINATION of diameter and pitch that for your boat and engine and how you will use the boat. So you are one of the few people who is willing to change the diameter (yeah!!!), only in this case I am afraid you selected a combination better suited for a pontoon boat.

3) Pitch is not pitch is not pitch. As my case hopefully illustrates well, there are a great many variations between manufacturers and prop designs, such that the pitch vs. speed equation is more appropriately used as a general guideline for selecting pitch, but not very good as a predictor, especially when crossing from one manufacturer-prop-design to another.

4) Don't underestimate the stock prop. The engine manufacturer knows the characteristics of his engine (i.e. where the power band is etc.), and often does a good job providing a range of diameter-pitch combinations that work well for his engine and a range of boating applications. My stock Tohatsu prop seems to be pretty close to ideal for me.

After talking with the engineer yesterday, the 10.375 x 15 HUSTLER makes a lot more sense to me as far as getting the right RPM at the speed I have now (note the substantial diameter DECREASE to get the rpm's up), but I have doubts about hole shot. There are a lot of other variables (how much does a particular prop cavitate or slip) that also come into play. All of which leads me to the last thing I've learned.

For most of us, there's not much getting around just trying a lot of props until we find the right one. Damn. I'll probably end up with one HUSTLER ( I can exchange) and probably a 13P and a 14P Tohatsu. Oh well. Spares for a lifetime. A lot cheaper than a new boat and engine.

Thanks!
Towtruck.

Should have also mentioned.
The most efficient prop for a given top speed is the one that gets you there with the largest diameter. The larger the diameter, the lower the possibility of cavitation, and the larger the column of water. That is why I am concerned that the HUSTLER 10.375 x 15 is a poor choice. It may get me the speed I have now, but I will lose at the low end. Prop manufacturers often offer a range of propellers, and even though the propellers may be very good, that doesn't necessarily mean they have a good diameter x pitch combo for your particular needs.

 

[Tail_Gunner]

Re: Hustler performance vs Tohatsu prop. ???

Sorry if that post seemed a bit jaded, one thing that is of big importance is the hub size on your motor, i cant find the link that read a 12" dia barrel but if indeed it is a 12" dia going to 10.75" barrel would or could cause a lot of slip which i believe you are now experiencing...

----------------------------------------------------------------------

Engine:
91 Tohatsu M50D. Max RPM: 5700, gear ratio: 1.85


Manufacturer: Tohatsu
Description: 50 HP, 50C only (Thru Hub Exhaust & 13 Tooth Spline)
Horsepower: 50 HP
Year(s): 1987 - 1991
Max RPM: 5000-5700 RPM

 

[towtruck1]

Re: Hustler performance vs Tohatsu prop. ???

Thanks again Tail_gunner

Hope I didn't sound too preachy. But after all this hair pulling and wrong turns, I do want to share what I have learned.

My understanding is that the 'hub' is the part that the blades are attached to. I think the Tohatsu is 3.something inches. The original prop diameter is 11.0", and because it now seems that this prop is close to ideal, I should try to stay close to it. So yes, the 10.375 x 15P seems like too much of a diameter loss for efficiency.



As I mentioned before, Tohatsu now only has a 13P and a 14P (no more 13.5P), and the diameter has gone up a tiny bit to 11.1 for both pitches.
http://www.tohatsu.com/accessories/prop.html
It is possible that subtle advances have made these props a bit more efficient, such that I can now swing the 11.1 x 14. I suspect that it is also possible that they slip less, meaning the 13P will now give me about the same speed as my old 13.5P. Unfortunately, there's only one way to find out....

 

[Tail_Gunner]

Re: Hustler performance vs Tohatsu prop. ???

Thanks again Tail_gunner

Hope I didn't sound too preachy. But after all this hair pulling and wrong turns, I do want to share what I have learned.

My understanding is that the 'hub' is the part that the blades are attached to. I think the Tohatsu is 3.something inches. The original prop diameter is 11.0", and because it now seems that this prop is close to ideal, I should try to stay close to it. So yes, the 10.375 x 15P seems like too much of a diameter loss for efficiency.



As I mentioned before, Tohatsu now only has a 13P and a 14P (no more 13.5P), and the diameter has gone up a tiny bit to 11.1 for both pitches.
http://www.tohatsu.com/accessories/prop.html
It is possible that subtle advances have made these props a bit more efficient, such that I can now swing the 11.1 x 14. I suspect that it is also possible that they slip less, meaning the 13P will now give me about the same speed as my old 13.5P. Unfortunately, there's only one way to find out....

http://boatpropellers.iboats.com/To...s/331/?**********=136899856&*******=374325771



5311-111-13
11-1/10?
13?
3
Standard
< Product Info >
$76.99




Prop: H1-1013
Hub: 13
10-1/2?
13?
3
Standard
< Product Info >
$78.98




Prop: 992301
Hub: 112
12?
13?
3
Standard
< Product Info >
$96.71




Prop: H1-1413
Hub: 35
14?
13?
3
Standard
< Product Info >
$112.98




Prop: 41102302
Hub: 41102359
11-1/10?
13?
3
Standard
< Product Info >
$115.90




Prop: 41102301
Hub: 41102359
11-1/10?
13?
3
Standard
< Product Info >
$115.90






There in lies the confusion from 10.5" barrels's to 14.....

 

[towtruck1]

Re: Hustler performance vs Tohatsu prop. ???

Thank You

Actually I have a 50D, not a 50C, so the correct list is a bit smaller.
http://boatpropellers.iboats.com/To...andard&**********=617276491&*******=336377096

But your providing the link brings me to a realization! Look closely at the diameters of all the Aluminum 3-blade props. Only the HUSTLER has a diameter different from the current Tohatsu offerring. EXCEPT for HUSTLER, they are all 11.1! I think that tells me something.

Now look at 14" props.
http://boatpropellers.iboats.com/To...andard&**********=617276491&*******=336377096
Only two Al 3-blade props here. Again, the one that is not a HUSTLER is a 11.1 dia prop, just like the TOHATSU. Makes you wonder if SOLAS is the OEM Source for TOHATSU. I'm pretty sure Tohatsu doesn't actually makes their own props...

In any case, 11.1 sure seems to be the efficient diameter for this power and pitch range.

Also, I've never considered the Volvo before, but I'll bet it's a good prop. Those swedish have been mariners for a long time and are pretty technically up there. I wonder what the difference is between the two part numbers..

Thanks! I learn more every time.
Towtruck

 

[towtruck1]

Re: Hustler performance vs Tohatsu prop. ???

Just answered my own question about the two Volvo props...
http://www.gpcprop.com/catalog pdf/QL_Propeller_Catalog.pdf

The 302 is actually a 14P, not a 13P, so both of the links I showed in the previous post should have one Solas, one Hustler, and one Volvo in both the 13P and the 14P. And again, all but the hustler match the Tohatsu offerings in diameter. The Volvo is an interchangeable hub design, which rules it out as OEM supplier for Tohatsu. The Solas on the other hand is a non-interchangeable hub designs, which allows for it to be OEM supplier. Hmmm... the plot thickens...

 

[Tail_Gunner]

Re: Hustler performance vs Tohatsu prop. ???

1. http://boatpropellers.iboats.com/To...r=1991&**********=187977164&*******=374325771

2. http://boatpropellers.iboats.com/To...r=1991&**********=187977164&*******=374325771

Good luck i just had to change that pitch again....