Prop test data

[DejaWiz]

Heard a story of a guy mixing 4 gallons of E85 into a tank of 93 octane on his AMG and seeing power gains. Apparently the O2/knock sensor/ECM are picking up the octane increase (IIRC it blended to 98) and is either advancing timing or increasing boost or both.

Not suggesting most engines can do this (marine or automotive) but simply it probably really depends heavily on that particular motor and the design. Maybe it suffers, maybe it doesn’t?

It all depends on how the specific software mapping is programmed, and that will vary wildly from vehicle to vehicle, engine to engine.

 

[Potomacbassin’]

It all depends on how the specific software mapping is programmed, and that will vary wildly from vehicle to vehicle, engine to engine.

Yep - and forgot to add that was without a tune apparently. I found that hard to believe so that’s on “to-do” list to try it and put in the dyno... can’t believe anything you read these days!

 

[PartyBarge]

Yes, it could be the engine control system is ferreting out the actual octane AND taking advantage of the increase. My 1993 Allante had full onboard computer diagnostics. It was no small chore to figure out how to get into them and could only be done with a shop manual...but I did it. That Northstar engine was a premium fuel only version and the computer could figure out what it calculated the current fuel octane to be and displayed that number. If I put mid-grade in, the ECM knew and performance suffered. The engine ran fine, but it wasn't going to snap your neck...

We have a flex-fuel vehicle that had stated on the window sticker (in very small print) that E85 would reduce the EPA MPG and range by 25%. Considering that the EPA numbers are based on E10 and that vehicle looses about 5% from E0, I've never seen E85 to be close to cost effective in any of the states I drive (against either E10 or E0). I was born and raised on a farm, but I can proudly say I've never bought E85. Don't know when, but I'm confident that someday we will sorely regret depleting prime farm ground to produce motor fuel. Not to mention that it's a crazy economic fiasco and is only a semi-competitive fuel due to tax and regulation bias. Modern engines don't need what alcohol offers.

 

[Potomacbassin’]

Finally able to get the Q3 datalogged and here are the results. I will say that while this feels like a great prop and the better top speed has me very happy, looking at the data I'm conflicted which is no surprise given how different each of these props are. It just goes to show - as with many things in life - there are tradeoffs with each prop and you have to really define what your primary objectives are. Further, you can overthink this to death (this thread is exhibit A) but the data is quite revealing and I'm glad I went through the process. Hopefully you all have benefited in some way as well... I appreciate all of the input and ideas you've provided along the way.

Now that 4 props are being charted it's just getting too convoluted so I'm separating them out by metric. ONE CAVEAT, this latest test was with 3/4 tank of fuel instead of 1/2 tank, so that could skew the Q3 data slightly. First MPH:



MPG



GPH



Slip



At this point there are some basic takeaways 1) the Reliance is just not enough prop for big motors and the data proves this out, 2) the SWS 19p does a lot more work than all other props but is too much for an F250 (ran out of RPM) and 3) the Q3 seems to be a reasonable compromise between the two. Slip for the Q3 is pretty bad at low RPM likely due to the small diameter but really shines on the top end.
But I got to thinking - all of these charts are comparing MPH, MPG and GPH at equivalent RPMs. But what if I were to use MPH as the x-axis, because who really targets a particular RPM while operating the boat - aren't we typically looking at the speedometer? Don't we usually target one of two speeds - WOT or cruise?

The results were a bit of a let down for me on the Q3. First MPG:



And GPH



For this exercise I removed the Performance bulletin data to show only the 3 props that have been on the boat. It's clear that the 15 x 19 SWS is dramatically more efficient than the Q3 all the way up to 38 MPH and even then the Q3 is only marginally more efficient beyond that. Yes I can get more top speed from the unique blade design of the Q3, but when it comes to efficiency I don't think there is an effective replacement for diameter on a well-designed prop.

The questions are - is a little more top speed a worthwhile tradeoff for fuel efficiency in that sub-38 mph operating range? What MPH will I be operating the boat most in? What other test data should be included, such as time to plane, low speed maneuverability, etc. These are things that only I can answer, but something to consider should you find yourself in a similar quandary.

Last comment before I sign off, I do still plan to raise the motor a couple of holes which will likely better the numbers across the board for the given test conditions (straight line runs, 1-2 footers). But it has me thinking that given the expected pickup in RPM (200-300?) I may benefit from trialing a larger diameter prop such as the 15.25 x 18 or 15.5 x 17 SWS. At this point I think they'll have a cure for COVID19 before I figure out my prop...

 

[DejaWiz]

WOW! Thank you for taking the time and putting in the effort for all this great data!

 

[PartyBarge]

OK, so you stuck with red for the Q3, but what's the deal with changing the colors of others from chart to chart? Not sure why you are conflicted. Could it be you are changing your initial, stated, target due to over-interpreting a wealth of data and anticipating there may be a better yet over-all result with an SWS of perfect pitch? (sorry couldn't resist writing "perfect pitch" as if that exists) For me, speed and acceleration numbers with heavier loads would be important, but maybe not so much for you? Those qualities would likely point to a lower pitch SWS too. Anyway, guess you know your MPH/X-axis charts are only somewhat different looks of the same results?

To be sure, thanks for all your work and investment in this! The good news is that you still have two excellent choices for the engine mounting adjustments. Both have RPM "headroom" and good slip numbers (so far) and I would be interested in some accel data too. One of our sons just bought a 23' Key West with an F250. It currently has some crappy aluminum 4-blade. When he finally digests the cost of the boat and rigging (life can't go on without a 36 volt GPS based tolling motor), I expect to steer him toward a 17p SWS (maybe 16p as he will be carrying lots of gear). Ooh, Ooh just occurred to me..........that could be a combination B-day/Christmas gift.........

Most certainly this has been some fun. Do try to let us know where you land. Cheers! I'll make mine scotch.

 

[Potomacbassin’]

I had the feeling my color choice would become the subject of commentary. Call it “prop change weariness” where mentally there are diminishing returns as the post count grows. From here on out any victories will be Pyrrhic based on calorie burn alone.

I too plan on putting that 36v wizardry on the bow, so while you are buying?? Maybe I can scare up a bottle of Pappy or Willet from my bourbon obsessed friends and join you. Certainly if I can join the “50 MPH Club“ a special bottle will need to be procured to commemorate the occasion!

 

[Walter Kurtz]

Good morning from Florida
Not to take away from such valuable data provided by the OP but thought I’d give a little feedback on our new 23SSBXPA. With only me and a full tank (52 gallons) I was able to get 48mph.

ESP hull
17 P Enertia
Mounted 2nd hole from top
48mph at 5650 rpm
Trimmed minimally at .5–.7 (Sc1000 Merc gauge)
Light wind & brackish water.

The following day
loaded with 4 adults, 3 kids & coolers

44 mph at 5350/5400 rpm

Id prefer to be around 5500/5600 when loaded, so I’ve chosen the 16P Enertia which my dealer Seagate Marine has so kindly swapped out for us. He has the 15x15 also (Merc/BEN recommended prop) if we’re still not happy.
We love the boat and they’ve gone out of their way as a dealer to make and keep us happy customers.

 

[DejaWiz]

Good morning from Florida
Not to take away from such valuable data provided by the OP but thought I’d give a little feedback on our new 23SSBXPA. With only me and a full tank (52 gallons) I was able to get 48mph.

ESP hull
17 P Enertia
Mounted 2nd hole from top
48mph at 5650 rpm
Trimmed minimally at .5–.7 (Sc1000 Merc gauge)
Light wind & brackish water.

The following day
loaded with 4 adults, 3 kids & coolers

44 mph at 5350/5400 rpm

Id prefer to be around 5500/5600 when loaded, so I’ve chosen the 16P Enertia which my dealer Seagate Marine has so kindly swapped out for us. He has the 15x15 also (Merc/BEN recommended prop) if we’re still not happy.
We love the boat and they’ve gone out of their way as a dealer to make and keep us happy customers.

Which Merc engine?

 

[Potomacbassin’]

Great looking boat! Love the black on black. I really am rethinking my curved Bimini, it’s just not user friendly - it appears you have a sport tower type deal. How do you like it and how is the shade coverage versus regular Bimini (if you happened to compare)?

 

[PartyBarge]

Walter, thanks for the report. Slippage increased just a little bit with increased load, as expected (~3-4%). No big deal at all. Your change to a 16p Enertia should put you in about the best WOT RPM ranges both light and loaded with better accel too. Well played!

 

[Potomacbassin’]

Acceleration data for posterity. 1/2 tank of fuel, 1 person but choppier conditions. Unfortunately I was relying on my chartplotter which pulses speed data in 1 second increments and I don't have an analog speedo to measure fractional seconds. Still should paint a picture that it seems to be within range of other boats of similar size, power and prop. Also still have the motor mounted in #1 with the plan to go to #3 at some point in the next few months so hope to improve this a little more.

 

[PRaudio]

Acceleration data for posterity. 1/2 tank of fuel, 1 person but choppier conditions. Unfortunately I was relying on my chartplotter which pulses speed data in 1 second increments and I don't have an analog speedo to measure fractional seconds. Still should paint a picture that it seems to be within range of other boats of similar size, power and prop. Also still have the motor mounted in #1 with the plan to go to #3 at some point in the next few months so hope to improve this a little more.

Which prop did you settle on?

 

[Potomacbassin’]

I’m sticking with the Q3 17 for now. Once I swap the SWS 19 with the dealer I will also test that prop, but depends on what effect raising the motor has. If I pick up only a few hundred RPM I may go with a 17 but if it’s more then I may try the 18 based on the 5300 rpm I could turn with the 19.

I also have not added the trolling motor and associated batteries and still considering power poles, so the additional weight may offset some motor height gains.

 

[PartyBarge]

That accel data should be plenty good to see any significant differences, good job. I found an SWS II 17p on Ebay that looked pretty good. It's now on the way to our son. I'm sure he'll appreciate the mid-range performance for an SWS versus a Q3 with very nearly the same top end (for a boat that tops at only ~50 MPH anyway).

I expect to have at least some idea how it works on his Center Console (23' Key West. F250) with a similar weight and drag profile to your pontoon in a week or two. The data won't measure up to your captures, but may be worth a look. BTW: that prop is very commonly used on 23' CC's from 3400# through 4800# (250 through 300 HP) with very good results. Our son's boat, tricked-out and loaded, hits the middle of that range.

Just a heads up (you may already know), 16p or 18p SWS's are hard to find.

 

[jhill]

Acceleration data for posterity. 1/2 tank of fuel, 1 person but choppier conditions. Unfortunately I was relying on my chartplotter which pulses speed data in 1 second increments and I don't have an analog speedo to measure fractional seconds. Still should paint a picture that it seems to be within range of other boats of similar size, power and prop. Also still have the motor mounted in #1 with the plan to go to #3 at some point in the next few months so hope to improve this a little more.

View attachment 27866

View attachment 27867

These boats kick butt! 25 mph in 5 seconds is pretty good hole shot for these large profile crafts. Nice job collecting data!

 

[Potomacbassin’]

That accel data should be plenty good to see any significant differences, good job. I found an SWS II 17p on Ebay that looked pretty good. It's now on the way to our son. I'm sure he'll appreciate the mid-range performance for an SWS versus a Q3 with very nearly the same top end (for a boat that tops at only ~50 MPH anyway).

I expect to have at least some idea how it works on his Center Console (23' Key West. F250) with a similar weight and drag profile to your pontoon in a week or two. The data won't measure up to your captures, but may be worth a look. BTW: that prop is very commonly used on 23' CC's from 3400# through 4800# (250 through 300 HP) with very good results. Our son's boat, tricked-out and loaded, hits the middle of that range.

Just a heads up (you may already know), 16p or 18p SWS's are hard to find.

Well, at this point I feel pretty close to dialed in so I have the benefit of time - as long as it arrives by Christmas! Maybe Mrs. Claus will throw in a 100 hour service in the ol’ stocking.

I do think the SWS is a very good, efficient prop, and while top speed is great for bragging rights and bass tournaments, the every day joe is probably operating in that mid-range the vast majority of the time. I’ll try to do one more test with whatever I end up with and post results. I’m sure it will be splitting hairs with the nod towards whatever activity the user’s boat sees most of. Different tools for different jobs.

 

[PartyBarge]

Exactly! And your thoughts are reinforced by a great many running SWS (or similar) props for more moderate speeds and heavier pulling than bass boats run. Typically, saltwater fishing is far more demanding of an economical mid-range than freshwater. It's a wonder that an SWS of proper pitch can also offer a top end within ~5%, or less, of any prop for boats/pontoons in this class.

Worth noting that whatever accel and slip differences you see between props with a light operating condition, they likely will be expanded as boat weight/drag goes up.

Don't despair. If it weren't for splitting hairs, we wouldn't be doing much this. However, sometimes the hairs turn out to be pretty big. For our Stingray we have a 24p Turbo (three blade) that beats our 23p High5 (five blade) everywhere except acceleration and stable pulling under variable load (ie, slalom skier). Putting 3+ adults in the boat and deepwater starting a slalom skier makes the Turbo nearly unusable.

 

[JDB]

It's a wonder that an SWS of proper pitch can also offer a top end within ~5%, or less, of any prop for boats/pontoons in this class.

Exactly !!

 

[PartyBarge]

Exactly !!

OK, you made me do it. Had to check what gear ratio you likely have to pull an SWS 20p. Is 2-to-1 pretty close?