Propping Chart and information.

[Bryden24shp]

From the number of PM's I get on propping, I just wanted to post this up for anybody contemplating a prop change. Ed, would you want to sticky this? I posted it as a reply, but maybe it deserves to be seen as a subject.
Thanks!
Bryan...

http://www.go-fast.com/Prop_Slip_Calculator.htm
Here is the best tool to use. Take notes on GPS speed, RPM's at planing,midrange and top speed and trim settings. Keep your loading as close to the same every time you test. You want to use the calculator to determine slip. You want to achieve the highest speed in the max RPM range, with the lowest slip number. Its a good way to trim your fuel usage as well. The least slip, the more economical your motor will run. You are trying to get to 6 to 12%. slip. Up to 17% is ok. But you must be in the upper RPM recommended by the manufacturer, too much overloading the powerhead can be devastating.
Starting point, find a buddy with an equivalent prop. (15 3/4 X 17 Mirage Plus, for instance) Spin it and note
After comparing your notes with the slip calculator a few times, you'll start to see the science in it and the results from your swaps.
After a few deep water prop swaps, you'll be a pro!
As I have said a hundred times....
I LOVE PROPPING!!!

[pond tuuunes]

Probably my fault Bryan, lol. Whenever someone askes, I recimend you. Sorry JT

[HandymanHerb]

From the number of PM's I get on propping, I just wanted to post this up for anybody contemplating a prop change. Ed, would you want to sticky this? I posted it as a reply, but maybe it deserves to be seen as a subject.
Thanks!
Bryan...

So I'm not good enough huh

[Bryden24shp]

No problem, JT! Thats fine! I enjoy helping...
Herb, I just figured you were probably too busy cleaning up those pontoons.
While Ed was just cleaning his camera lens. Keep her clean Ed! We like the clearest pics possible...

[fergusmj]

Any thoughts on if it would be worthwhile for people to post their boat specs, prop, engine size and top speed / rpm? This could be put into a matrix for people to cross reference.

Example, I have a 24' Tritoon (sport tube) with lifting strakes on the inside of outside toons, 150HP Optimax, 15P Enertia SS prop. Not sure on top speed as I'm still on break in for the rebuild.

Just a thought.

[TDJ2591]

I think a chart showing the actual performance of various prop/boat/motor combinations would be great. I just bought a used 'toon and am having a challenge figuring out the optimum prop for it. There's no place to borrow props nor any nearby dealers and I can't afford to keep buying and testing props, plus my boat is 2 hours from my home. I would love to know what others are running on a similar boat/motor combination. A chart that included the make, model & size boat, twin or tri-toon, strakes or TAP, motor brand, HP and 2 or 4 stroke, size and type prop along with RPM and GPS speed would be invaluable.


2005 Crest Caribbean, 2006 135 Honda 4 Stroke

[18pontoon]

Got a 18' pontoon with a Suzuki DF70 on it. Just got the motor and have a 13.75x15 on it. New 14x10 came in and I'm about to try it this afternoon. The 15 pitch only did 4k RPM at 12 mph (although it did hit 4700 at 18mph on calm water). I will take notes to use the chart. Great info

Edit- 14x10 works great. 5800 RPM at 18MPH with a very light load. Will have to see how it runs this weekend with more people and coolers

[Bryden24shp]

Edit- 14x10 works great. 5800 RPM at 18MPH with a very light load. Will have to see how it runs this weekend with more people and coolers

Good Job!!!

[Diamondjim]

I, too, am having a hard time propping. I have a 25' Aloha Sundeck twin toons and a new Yamaha 150 4 stroke. I have a Yamaha Reliance series prop, 14,5" diameter with 15" pitch now. I am running 30 mph but am only turning 5300 rpm @ wot. That is the lowest pitch in that prop family.
I just tried a Metc. Enertia 15.6" diameter @ 13" pitch. It also only turned 5300 rpm and I lost about 2 mph. All speeds are measured with gps. Also, the Enertia prop barely rubbed the trim anode only when underway, I knew it was close but didn't rub when spinning by hand.
I am certainly open to suggestions and it doesn't make me any difference if it is SS or Aluminum. I need to get this motor spinning about 5700-6000 rpm. The prop I have and the Merc prop are both stainless. Thanks.

[Bryden24shp]

Hey Jim I got your email, hope this helps. I'll just post here instead of email so others can chime in on my thoughts. I think the added diameter of the Enertia cancelled out what you thought you would get with the lower pitch. I would see if the dealer can hook you up with something like a 14X15 or a 14 1/2X13, something like that range.

[Diamondjim]

Thanks, Bryan. We are thinking alike,I do think I will need a 13 pitch max if not even an 11. I thought the diameter of the Enertia was going to limit my rpm. Fortunately my dealer has been great at working with me on it.
Also, I get a lot of compliments on the EZFenders and am trying to send some business to you. Thanks again for the quick reply, I will post the final outcome along with my performance numbers.
Have a good week. Jim

[Bryden24shp]

Thanks Buddy! I appreciate that! We have been doing really good with the business and can't wait until the new building is up for the business and to store the boat in during the off season. I need a place where I can start doing more boat projects and this will work great! I've got some some cool changes for the Premier in mind and no place to make them. You know me....Always tweaking, looking for that extra something!
If you need anything, Jim. Give me a yell!
Bryan

[MattGent]

OK I've used these prop calculators plenty of times before, even have one in a spreadsheet on my computer. But all of my data is on speed boats (think 90mph) and runabouts/skiffs. These all run in the 5-15% slip range.

I'm repowering my pontoon from the old-n-busted 9.9 johnson to a new-n-shiny 25hp Suzuki. The boat is a ~16' Stardust which I rebuilt a couple years ago. http://forums.bateau2.com/viewtopic.php?f=10&t=24678

I never had a tach on the Johnson, nor a speedo, and it never ran right anyways. So I have to go by public data in picking a prop for the new motor.

This setup from Yamaha http://yamahaoutboards.com/sites/defaul ... be.tmp.pdf will be very simlar to mine: slightly bigger boat, similar weight (mine a bit lighter), nearly the same gear ratio (2.08 vs. 2.09) and max rpm. The problem I'm having is to match the Yamaha #s, you have to assume something like 40% slip. This is way out of my data range.

Now I know that the high-thrust motors are run on pontoons for this very reason, but 40% seems huge. Here's one with a T25 http://yamahaoutboards.com/sites/defaul ... 3c.tmp.pdf and even that runs at ~20% slip but gets the same performance as the F25.

So can anyone else provide a data point for a ~15mph pontoon with a 25hp engine? Do they really run with huge slip #s? Maybe the F25 prop isn't accurately 9" pitch?

Guessing I should start with a suzuki 9" and see how that runs?

Thanks
Matt

[MattGent]

A couple more data points, this 16' pontoon with a 25Etec only goes ~11mph, also at 40% slip.
http://www.evinrude.com/Content/Pdf/neu ... /PE982.pdf

This one with a 30 goes ~17mph at almost 30% slip (light boat, only one person on board).
http://www.evinrude.com/Content/Pdf/neu ... /PE722.pdf

Last one, etec40 with the large gearcase. 2.67 ratio and a much larger prop (13-3/4x13") at 5% slip and 25mph
http://www.evinrude.com/Content/Pdf/neu ... PE1040.pdf

Hard to make sense of the slip numbers, particularly the large gearcase etec40 and the T25 which should be similar.

[Bryden24shp]

Hi MattGent! Without a tach its really hard to start propping. Can you hook up an old one off EBay or some place just to as a test tach? Then at least we know what end result we are looking for.