Piranha Composite Propellers

computer-rooter-

Bad news two ways:

The 2 stroke Suzi 100 has a gear ratio of 2.08:1 and the Honda 90 four stroke 2.3:1 so the ratios are different, and it's unlikely the same prop pitch will run on both engines with the same boat, and

The Suzi and Honda have different hubs, so unless you buy a prop with a replaceable hub (of which there a quite a few), you've got that problem, too.

??????? Joe.
 
Sea Wolf":3oiaprki said:
computer-rooter-

Bad news two ways:

The 2 stroke Suzi 100 has a gear ratio of 2.08:1 and the Honda 90 four stroke 2.3:1 so the ratios are different, and it's unlikely the same prop pitch will run on both engines with the same boat, and

The Suzi and Honda have different hubs, so unless you buy a prop with a replaceable hub (of which there a quite a few), you've got that problem, too.

??????? Joe.
Click to expand...

See? That's why I ask the pros!
 
Now that the dog gone thing is on where is the dog gone data?
I am spinning the big 20 pitch with my Suzy 90 and I love it but I may step down a bit to conserve a little fuel.
The Suzuki 90 was the only one in it's class that would turn that 20 pitch screw and it pops my loaded for Tuna Angler with 4 adults (Supersized) a teenager (XL), 500# of ice, 400# of Tuna and all our dear up on plane without any problem at all.
I am interested in this 4 blade prop so please do share...

Is this an adjustable pitch prop?

Esplaine please...
 
This ain't cat food buddy.... no sir. In fact I ran out of Tuna this year and thank goodness for friends cause one of them gave me a case of shorts.

The Albacore we catch in the Pac NW is the best in the ocean.

If we should ever cross paths you will have to taste some for yourself.
Those who have tasted my torched Tuna treats always ask em to make em again, and they go faster than I can make them. The smell of hair burned off the hands of those reaching in early to grab them doesn't even put people off and I am starting to get used to it (joking).

Looking forward to the data.

By the way, 400# split 3 ways goes faster than you can imagine.
Tuna is good.... if you have never had home canned, you have been eating cat food. Not that there is anything wrong with cat food, it's just that when you figure out it is cat food you tend to feed it to cats.... or maybe your inlaws... and that is only because they were outlaws before they were inlaws... :D :twisted: :lol: .
 
My brother commercial fishes tuna, crab, and salmon out of Florence, OR. for his fish store and restaraunt. Sometimes, if I'm REALLY good, he sends me a can of his private label tuna or even better -- tuna pepperoni. I agree that anything less is really cat food, and that NW tuna is the best there is!

I didn't think a c-dory had the range to get out to the tuna though. I have a 50gal main tank and about 18gal in reserve, and with my fuel economy, I limit myself to 100 miles round trip on the main engine. How do you manage?
 
computer-rooter":3m9x46y1 said:
...I didn't think a c-dory had the range to get out to the tuna though. I have a 50gal main tank and about 18gal in reserve, and with my fuel economy, I limit myself to 100 miles round trip on the main engine. How do you manage?
Click to expand...

I have a 58 gallon main tank and carry 18 gallons. I have fished from before dawn to dark in teh Summer hours and never had less than 12 gallons remaining.

I have trim tabs and a fuel flow meter installed now and expect to be able to economize even more.

My Suzuki 90 4 stroke is quiet and really sips the fuel. In fact I was pulling up to the marina gas dock in Newport and teh attendant asked me if I knew that my engine had a recall out... I said, no.... he said, Yea, they don't burn enough gas... :shock: :lol:
I have been as far as 70 miles off shore. I love it out there...
 
I tried to trim the TTs (ooooh, nice!)
Click to expand...
Wow! I need a better class of friends!
Come to think of it I think that last statement was a little too much information :teeth .

Thanks for posting the data you did collect... I am gonna hold off on asking for pics of the above quoted procedure as this is a family oriented site...

What prop pitches are available for that contraption?
Maybe I best just look it up?
 
Dan,

Those are very interesting numbers. With my Johnson 90 and stock prop I ran a little faster before adding the permatrim. A couple mph on the top end does not matter that much to me so no problem.

I have a compro prop that fits but like you said earlier it is too small. I picked it up cheap to have as a spare.

Thanks for doing the initial trial. Now, I think I would like to get one. Where did you get yours?

Also I am wondering if the 18 blades are going to be too much?

Steve
 
Okay guys, I spent the money and got the Pirahna prop with 2 sets of blades. I only had a short time to try them out Sunday but the first numbers look good. My boat is fairly light right now, only about 25g gas, no water, no food, no cloths, no toys. Just pots, pans, and 2 people.

My stock prop is a 3x14x19. I bought the 4x14x18 and 4x14.5x16 Pirahna.

RPM S19 P18 P16 (speed in knots)
2000 6 6.2 5.9
3000 8.6 9.6 8.8
3500 12 14.2 12.7
4000 17.9 17.9 16
4200 18.7 20.5 NA

WOT:
Stock 5200/25.6
P18 5100/24.5
P16 5400/24.1


These numbers are for a single run with each prop with unknown current. I am sure they would change for different conditions and loads. It does seem that the Pirhana 18 provides more speed for the same RPM/fuel than the stock prop. I am thinking that the P16 will be a good prop for Lake Powell.

How do you calculate the prop slip? Any comments on these numbers?

Steve
 
Steve-

Here's how to figure prop slip:

1. Take the engine RPM and divide it by the gear ratio to get the RPM of the prop:

5000 RPM divided by 2:1 = 2500 prop RPM

2. Multiply the prop RPM times the pitch to get the forward travel w/o slip:

2500 RPM x 16 inches = 40,000 inches per minute.

3. Change inches to feet by dividing by 12:

40000 divided by 12 = 3333 ft per minute.

4. Knowing that 60 mph = one mile per minute, and one mile = 5280 ft,

divide your ft per minute by 5280 to get your fractioal speed of 60 mph:

3333 divided by 5290 = 0.6313 of 60 mph, so

5. Multiply 60 mph by the ratio (decimal) above to get the speed in MPH w/o slip:

60 MPH x 0.6313 = 37.8 MPH (theoretical speed, w/o slip)

6. Find the loss due to prop slip in MPH by subtracting the real speed from the theoretical speed:

Your observed speed = 30 MPH, so

37.8 MPH minus 30 MPH = 7.8 MPH loss due to slip

7. Find out what fraction (decimal) is lost by dividing the theoretical speed by the loss due to slip:

7.8 MPH divided by 37.8 = 0.206 fraction/decimal lost to slip.

8. Multiply this fraction/decimal by 100 to get percent:

0.206 x 100 = 20.6% slip

***When the propellers are pretty well matched to the engine and the load, the slip will be about 10-15% in planing hulls at speed. The amount of slip at displacement speeds will usually be much greater.

****************************************************************************

Hope this helps! (Was lots of fun!)

Joe.

 
MIKE-

YUP, IT WORKS FINE!

JUST PLUG IN ALL BUT ONE NUMBER (IN THIS CASE SLIP %), AND THE CALCULATOR FIGURES THE REST!

EASY!!! (Almost TOO easy!)

JOE.
 
You would definately want the 16" or maybe even a 14" prop to get WOT at Powell. I don't know what your engine's WOT should be, but many modern outboards are in the 5500 to 6000 RPM range.
 
Thanks Joe for the run through the numbers. Makes sense once it is explained.

Bob, The Johnson has a WOT range of 4500 to 5500. Don't know why such a large range but that is what the book says.

Steve
 
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