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Prop test data

Potomacbassin’

Potomacbassin’

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Thought I would share some data logging and some interesting observations.

Background

Boat is a 2020 23SSBXP with SPS+ and F250xca. Dealer propped it with a Yamaha Reliance 14.25 x 17 which I knew was incorrect based on the Yamaha prop selector tool. Seat of the pants dyno also told me something was awry and likely under propped. After fighting with the dealer they agreed to swap it out for the recommended SWSII 15.25 x 19 (although I asked for the 15.5 x 18 but it was back ordered). But before the swap happens I wanted to baseline the original prop to 1) verify with data any improvement gains with the new prop and 2) use to support my position if there is a continued fight with the dealer.

Ran it today and logged every 500rpm. Just 1 person, half tank of fuel, light wind (5-8mph) and 90F. I found a quiet cove so waves were not a variable. Below is the chart showing MPH, GPH and MPG (solid line). I also plotted data from a Yamaha performance bulletin for a 2350 QCL with a F250xca and 15.75 x 15 to compare (dotted line).

Observations:

1) The heavier QCL had a higher MPH across the RPM band, I suspect because of the proper diameter prop and less slip. Confirms my 14.25 is waaaay under diameter for the motor

2) My boat takes longer to get up on plane, around 3000 rpm vs 2500 for the QCL. Fuel efficiency thereafter appears to be similar up to 6000

3) The QCL fuel consumption is greater across the RPM band, likely due to the prop doing more work, but having more drag from the higher diameter. Also heavier boat.

4) QCL gets up on plane and MPH is linear thereafter. On my 14.25 you notice it struggles until about 4000 rpm, then really spikes and gets up to top speed. Both boats max out around 45-46mph at WOT.

These are my thoughts which could all be wrong, but the graphs themselves tell a story. Once the new prop is installed I’ll datalog another run, and finally raise the motor one hole and log that as well.

Should be fun. Lastly - go with your gut if you think something is off and don’t let the dealer blow you off. You know your boat best, and even if they end up being right, odds are they didn’t get it dialed in perfectly the first try.

thanks

EEDEED3C-7226-47DD-A81E-4EEC48121D8E.jpeg
 
Potomacbassin’ said:
Lastly - go with your gut if you think something is off and don’t let the dealer blow you off. You know your boat best, and even if they end up being right, odds are they didn’t get it dialed in perfectly the first try.
Click to expand...

Very true. My dealer told me they water tested 3 different pros and chose the "best one." That was a lie. No dealer is gonna spend that kind of time. My suggested prop was spot on in both RPMs at WOT and top speed in a real on-water test. He accused me of lying, to which I asked, "What do I have to gain by lying about this?" He swapped out the props with no further conversation.
 
I'm really lucky to have a knowledgeable dealer that can put the correct prop on for the boat/motor combination. The 2 boats I've bought from him hit 5900 to 6000 rpm with a light load with the first prop He supplied. He also owns a bennington as well. So, I'm sure that helps.
 
Hearing all these dealer horror stories, I feel lucky to have two good dealers “nearby” the one I bought from propped it right and mounted the motor in the right hole. And the one that I take her to for service has been Johnny on the spot. No significant wait times, Easy warranty claims and a reasonable price.
 
Appreciate the input this is great info. I talked with my dealer and he’s agreed to allow me to try a couple props to get the new boat dialed-in. Same boat as yours Potomac but with the open arch and the ESP perf package & 250 Merc. Not sure how much difference the xtra surface area of the middle toon will make for top-end, but I’ll post some basic numbers when I can. I’m leaning more towards a 17 p prop vs the recommended 15.
 
I think I read the ESP gets up on plane faster, turns better and drafts less, but is a little slower on top speed vs the SPS+ due to weight and larger “pad” at WOT. I could be dreaming that as well.

I think a 17 in general will have a 1/4 or 1/2 less diameter than the 15 so it should have better top end at the sacrifice of holeshot and time to plane. Since we don’t do water sports I’m leaning towards top end and cruise efficiency. I know the 19 won’t give me that but worth testing so I know what the upper limit is. Will likely end up with a 18p or try one of the Merc props.
 
I heard the same about the ESP weight, but only for the R/G/Q 23 & larger boats is the way I understood it. I might be wrong though lol. I was told that the ESP for the 23 SXP is not the same beefy ESP that is built for 300HP and UP. The 23SXP with ESP or SPS+ both max out at 250Hp. This was as of last month according to Bennington. Maybe someone else knows more and can chime in.
 
Wow, you are taking a pretty big swing by moving up so much in pitch AND switching to the Saltwater-series prop! After looking at the Yamaha Performance Bulletin, seems to me they are correctly using the salt water prop (with 15p) achieving very low calculated slippage (WOT). That is expected with a design intended for high load and moderate speed. Your current calculated slippage is ~21%. Nearly wiping that out PLUS an increase of 4" in pitch from the Yamaha test is not the making of a happy result. Doubt you'd be happy with an 18p either....just my humble opinion....

I can see that the allure of 50+MPH for your pontoon is enticing, but IF that's possible, the sacrifice of the overall boating experience is likely to be a bit much....

Other than that, I enjoyed your analysis. Bring slippage into your work.
 
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Thanks for the comments, slippage is not something I’m totally educated on so I’ll follow through on your recommendation.

As far as pitch goes, I also agree that 19 is likely too much - but what is curious is the Yam online prop selector has the 15.25 x 19 as a recommended prop for the motor and hull type. This is with the performance goal set as “all around”. I’m open to trying as many props as practical to get it dialed in, it’s almost like a marriage for life so better pick the right one!

Will report back findings.
 
Updated slip chart, not sure if it looks right but I checked it against the Merc online calculator.

Any takeaways?



For me it would seem the current prop is horribly efficient up to 5000rpm. The 15.75 x 15 gets down into the 20% range at 2500 rpm which is where it appears to get up on plane.

BC12279E-FE56-408B-8350-661A20919F78.jpeg
 
Wondering how much of a top-end loss there is between 17 inch vs 15 inch pitch props as a %. Here’s an example. I test run my boat with 2 people/half tank fuel & get top-end 48 mph with the 17P & 45mph with the 15P. Once the boat is loaded with 6 people and full fuel, do you think the 15P prop will lose as much top-end (as a %) opposed to the 17P prop?
 
I have a 2018 23SSXP with a 200 Verado, The best I can get wot, is 39 mph @ 5500 rpm,, with 2 ppl and half tank of fuel, I have a SS 15x15p prop, which the dealer put on,, I really think this boat should go faster,, I need help
 
Bob V said:
I have a 2018 23SSXP with a 200 Verado, The best I can get wot, is 39 mph @ 5500 rpm,, with 2 ppl and half tank of fuel, I have a SS 15x15p prop, which the dealer put on,, I really think this boat should go faster,, I need help
Click to expand...

What brand of prop? I have a 16p Enertia on my 2017 24’ SSBXP SPS Mercury Verado Pro. Prior to Sea Legs I was 43-44mph WOT at 5900 rpm. With your parameters: 2 ppl & half tank on calm waters. That has dropped now with Sea Legs. However, I am still pulling 35-39 depending on conditions, fuel and ppl.
 
Good question Walter - everything I’ve read from here, THT and other boards is that there is no real way to calculate these things. A lot of trial and error, which is why I think Propgods has a good business model with their prop swap deal. My guess is our 250’s can handle quite a bit of blade area, cup, angle of attack - but loaded in your scenario the 17 will probably lose a little more RPM than the 15. Not sure how the math works out where lower RPM but higher pitch might equal same speed?? That’s why I’m just going to throw a bunch of props on it and datalog and see where the data leads.
 
Last time I checked with Propgods he using primarily Mercury Props and no SWS2 stuff so he was out right there for me.

I don't think you will find anything appreciably better all around than the 15 1/4 X 19 SWS2 and there is also a ~40 HP Tuneup available for your motor if that appeals to you.
 
Vikingstaff said:
What brand of prop? I have a 16p Enertia on my 2017 24’ SSBXP SPS Mercury Verado Pro. Prior to Sea Legs I was 43-44mph WOT at 5900 rpm. With your parameters: 2 ppl & half tank on calm waters. That has dropped now with Sea Legs. However, I am still pulling 35-39 depending on conditions, fuel and ppl.
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I have a 15x15 Enertia SS I dont know why I should be getting more MPH out of the Motor it's a Mercury Verado Pro, so it has the power..
 
Bob V said:
Everything is clean I keep my toon clean I just think I have to get my RPM's up and Can't figure out how to do it.
Click to expand...

Is there any chance it involves your motor mount? Perhaps too low in the water creating too much drag? I agree, seems like your RPM’s would be up with that particular prop. Hmm....
 
which hole is number 1,,The top or the bottom,, I just looked at my motor and it mounted at the top hole on the mounting plate
 
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