Prop test data

[JDB]

Sorry PartyBarge I didnt mean to mislead you or anyone else.
When I mentioned overdrive I was talking about the propeller itself, as that is essentially our final drive gear ratio and
the 52 - 5300 RPM I'm turning at WOT effectively works like an overdrive.

 

[[email protected]]

I have a 2015 bennington gsr 2250 with the elliptical package. I have a Mercury 250 Verado with a 17 pitch Enertia prop. I am only getting up to 5700 rpm, should a get a smaller pitch prop?

 

[Vikingstaff]

I have a 2015 bennington gsr 2250 with the elliptical package. I have a Mercury 250 Verado with a 17 pitch Enertia prop. I am only getting up to 5700 rpm, should a get a smaller pitch prop?

In theory, if you drop to the 16 pitch, your RPM’s are probably going to increase 250-300. Again, on paper, you should have just enough room to do so before hitting your RPM max at 6000.

Question: is your current RPMs of 5700 at WOT on a light load? If YES, and if you can test a 16p Enertia for free, then it might be worth it. However, since you are very close to at max now, I don‘t know how much you’ll gain vs. the cost of another Enertia prop. As close as you are now to your RPM limit, I certainly wouldn’t spend money to test it.

 

[[email protected]]

Fully loaded, 54 gallons of gas and 4 adults.

 

[Vikingstaff]

Fully loaded, 54 gallons of gas and 4 adults.

Then I would not change up prop myself. Typically you want to track your RPM at WOT on a low load because your RPM’s will be higher. You want the HIGHEST your RPM’s will go to be as near (but under) your motor limit as possible. If you are already at 5700 RPMs when fully loaded, then the reality is you are likely at, maybe even slightly high, for RPM’s under a light load.

IMHO, you are likely all set based on the additional information.

 

[PartyBarge]

JDB, no worries. Recent F250's typically are running 1.75 gears. Your SWS 20P at 2-to-1 would be roughly equivalent to a 17.5p with 1.75 gears.

 

[PartyBarge]

OK, finally a little follow up on the SWS II 17p I sent to one of our sons for his 23' Key West CC with an F250 (the boat has bottom paint). Motor mounting is up one hole from full down. Prop at time of purchase was a Turning Point Hustler (aluminum 4-blade 19p). That prop at WOT and moderate load (five adults, full fuel) ran 44 MPH at 5300 RPM for a slip of ~19%. Guess that's not awful, but Yamaha bulletins pointed to possible improvement.

The "new" prop has only been run once with the family aboard (two small kids plus a modest amount of stuff), half fuel and water conditions were marginal. However, he did hit 47 MPH at 5700 RPM (calculated slip of ~10%). Onboard electronics show the mid-speed fuel economy is better, but there is no good data for that yet. I expected a bit more speed for a relatively light load, but water conditions and bottom paint were limiting factors...don't know how much difference the bottom paint makes...? He indicated that he thought more speed would turn up with better water conditions. He did say that he thinks the 4-blade was smoother at dead idle RPM, but feeling disappeared above idle. I've noticed that with a 3-blade versus 4 and 5 blade props on our Stingray too.

Early results point to the SWS as a worthwhile change. Expect he will get more out of the boat as he gets more experience with it. Have to wonder if a 17p Hustler might be a decent prop for that boat too....?

 

[Potomacbassin’]

I have read that even small protrusions like a thru hull transducer can cause an enormous amount of drag at speed, so I would imagine that bottom paint could have a noticeable impact if not perfectly smooth?

I’m surprised about that idle roughness - the SDS hub on my 19p was fairly quiet, while the Rubex on the current Q3 carries more vibration. When you say at idle do you mean while in gear or idling in neutral?

 

[PartyBarge]

Oh, definitely in-gear. Yes, estimates for the effect of bottom paint are all over the ball park, from nothing to ~10 MPH. Variables like speed range, type of coating and method of application are major players. On his boat (40-50 MPH class), the coating is not intended to increase speed and to last more than a couple seasons. It is a relatively new re-application and was professionally applied, so I expect done with some care. Those conditions seem to indicate a hit of ~3-5%. Best guess seems to be ~2MPH for his boat. He trailers so no bottom paint would have been best, but the boat was the right deal at the right time...

I suspect another factor for top speed is the large T-top. His boat has some sort of optional top, but I don't know any details.

BTW: Just thought of this, about three years ago I noticed a little vibration with the Mec High-5. Considered having it rebuilt, instead changed the plastic torque sleeve. The new one fit snuggly and cured the vibration. The SWS I bought was a used prop of unknown age. I suspect any hub, including the pressed-in type, can develop some run-out over time...only speculation, no measurements. Worth noting that stainless props are ~3x (or more) the weight of aluminum. Any runout would be more apparent.

 

[Potomacbassin’]

UPDATE

Finally was able to get the motor raised to #3 and datalog results. Executive summary:

• Increased fuel efficiency across the board as expected
• Increased top speed, although not as much as predicted
• Increased RPM, although not as much as predicted
• Other ancillary benefits

First off, the really good. Here is the chart comparing MPG for the Q3 in the #1 position versus #3. As you can see a fairly significant increase on the order of 5-20%:



The above chart compares MPG at MPH, but for those interested in gains at RPM (Q3R is "raised"), table below:



Yes the % gains are greater below planing speed, but even at my typical cruise of 5000RPM, 10% is a material increase and will add up over a 1,000 hour motor.

Now the "just good" - the boat joined the 50mph club (barely!), although I was hoping to get to 51-52. The boat has a generous coating of algae from sitting in the water all year so once cleaned up that might get me to my goal. And WOT RPM increased from 5700 to 5900 - again good, but a little disappointing (hoping to break 6K).



Lastly some ancillary benefits:

1) The boat turns much better especially at low speed since there is less "rudder" in the water. This is especially useful when maneuvering around docks and into slips.

2) With the motor higher out of the water the side-scan sonar has less interference. In the #1 position I was losing around 5% of the scanning view to the port side

3) Boat just seems to feel smoother and less vibration from the motor. Could be all in my head, but with less drag the whole boat just seemed "happier"

4) No ventilation. I trimmed up to over 50% and the prop was still biting. I could even try for #4, or better yet, make an investment in a jack plate so I can adjust on the fly. My guess is once I load the boat with a lot of passengers and the stern lifts, I will likely see some prop ventilation at 50% so a hydraulic JP could make sense. Economically, maybe not.

OK folks, I think that does it for me - I'm officially going on sabbatical from this little prop adventure and try to reap the rewards. Hope it has been helpful to someone and if anyone has any questions let me know, I'm more than happy to assist wherever I can.

Thanks,

 

[PartyBarge]

Sure seems to me that the "news" is better than you think. Looks like the RPM increase is all due to more speed/less drag and NOT increased slippage. Pretty tough to beat that deal. Also clean logs will easily gain a couple MPH, maybe 3-4 on your pontoon, that extra speed will likely put your RPM at or above 6k. Meaning, the good news is likely to get better. Good show!

 

[jhill]

UPDATE

Finally was able to get the motor raised to #3 and datalog results. Executive summary:

• Increased fuel efficiency across the board as expected
• Increased top speed, although not as much as predicted
• Increased RPM, although not as much as predicted
• Other ancillary benefits

First off, the really good. Here is the chart comparing MPG for the Q3 in the #1 position versus #3. As you can see a fairly significant increase on the order of 5-20%:

View attachment 28078

The above chart compares MPG at MPH, but for those interested in gains at RPM (Q3R is "raised"), table below:

View attachment 28079

Yes the % gains are greater below planing speed, but even at my typical cruise of 5000RPM, 10% is a material increase and will add up over a 1,000 hour motor.

Now the "just good" - the boat joined the 50mph club (barely!), although I was hoping to get to 51-52. The boat has a generous coating of algae from sitting in the water all year so once cleaned up that might get me to my goal. And WOT RPM increased from 5700 to 5900 - again good, but a little disappointing (hoping to break 6K).

View attachment 28080

Lastly some ancillary benefits:

1) The boat turns much better especially at low speed since there is less "rudder" in the water. This is especially useful when maneuvering around docks and into slips.

2) With the motor higher out of the water the side-scan sonar has less interference. In the #1 position I was losing around 5% of the scanning view to the port side

3) Boat just seems to feel smoother and less vibration from the motor. Could be all in my head, but with less drag the whole boat just seemed "happier"

4) No ventilation. I trimmed up to over 50% and the prop was still biting. I could even try for #4, or better yet, make an investment in a jack plate so I can adjust on the fly. My guess is once I load the boat with a lot of passengers and the stern lifts, I will likely see some prop ventilation at 50% so a hydraulic JP could make sense. Economically, maybe not.

OK folks, I think that does it for me - I'm officially going on sabbatical from this little prop adventure and try to reap the rewards. Hope it has been helpful to someone and if anyone has any questions let me know, I'm more than happy to assist wherever I can.

Thanks,

Wow....Big difference.....What year Benny, model, and engine do you have? Sps ? Just wondering about moving engine on my 2017 22 SSRCX F150 SPS from the #1 top hole (lowest in water) to at least the #2 hole

 

[Potomacbassin’]

Sure seems to me that the "news" is better than you think. Looks like the RPM increase is all due to more speed/less drag and NOT increased slippage. Pretty tough to beat that deal. Also clean logs will easily gain a couple MPH, maybe 3-4 on your pontoon, that extra speed will likely put your RPM at or above 6k. Meaning, the good news is likely to get better. Good show!

Better is a relative term - I was expecting a med rare blackened ribeye but got med well instead. Still happy - at least it's not cold liverwurst on Wonderbread. I still am owed a replacement for my SWS19 so there's always the prospect in '21 of another prop joining the party!

 

[Potomacbassin’]

Wow....Big difference.....What year Benny, model, and engine do you have? Sps ? Just wondering about moving engine on my 2017 22 SSRCX F150 SPS from the #1 top hole (lowest in water) to at least the #2 hole

Hey jhill - 2020 23SSBXP with an F250, SPS+. What is a little unique about this one though was a custom layout with the heavy dinette table instead of the L bench and 52gal tank, so it is pretty stern heavy.

I'm going to vote "yes" on moving the motor 1 hole based on my own experience, where I think I could even go to #4. But my mechanic gave me a little test which you may be able to use (or already know) - if you can get past 50-60% trim in the #1 spot without ventilating you can probably benefit from raising the motor. I could almost get 75% so I knew #2 was pretty much guaranteed, thus skipped right to #3.

Can't remember the spacing on Yamaha but it's somewhere around 3/4" per hole, so not a lot. Also something to consider, prop diameter and motor shaft length - larger diameter prop may limit your height (mine is a 14.5" D) and the F150 comes in both 20" and 25" IIRC. But I think that trim test should be your best guide.

I say give it a try, but I'm reminded by another recent post about spending other people's money!

 

[PartyBarge]

I still am owed a replacement for my SWS19 so there's always the prospect in '21 of another prop joining the party!

You may already know all you need to about an SWS17, but I hope to have some better recon for you later....OR....is that SWS19 still laying around? Clean tubes and the new mounting height might throw a different light on it.....

 

[Potomacbassin’]

You may already know all you need to about an SWS17, but I hope to have some better recon for you later....OR....is that SWS19 still laying around? Clean tubes and the new mounting height might throw a different light on it.....

I was actually thinking that if I hit the rev limiter after raising the motor I might give the 19 another go. But even if the clean toons get me above 6200 on the 17 it would only be temporary, and I’m not about to scrub the hull every month just for a few MPH. I’d be better off getting a Nizpro tune for that kind of effort!

I could put a jack plate on and really get that height right at the limit along with an 18 and maybe see another 1-2 mph? But again, I’m probably hitting the point of diminishing returns with my time and money, and the kids’ 529 plans haven’t seen a whole lot of love in the past 9 months! But good feedback, thanks PB!

 

[PartyBarge]

Yup, and the similar problem with a jack plate too. All it takes is a little ripple to cause the prop to unload and a functional test of the rev limiter. As for log scum, I carry two polypropylene stiff-bristle brushes (long and short handles). While having lunch at some island beach, I spend just a few minuets with them and over the course of a summer cover all wetted areas more than twice. The growth can be pretty fast in our warm summer waters. For our pontoon, any buildup costs noticeable speed (and, likely, economy). A run at top speed will clear some of the scum if it hasn't been there long, but not enough...

 

[jhill]

Hey jhill - 2020 23SSBXP with an F250, SPS+. What is a little unique about this one though was a custom layout with the heavy dinette table instead of the L bench and 52gal tank, so it is pretty stern heavy.

I'm going to vote "yes" on moving the motor 1 hole based on my own experience, where I think I could even go to #4. But my mechanic gave me a little test which you may be able to use (or already know) - if you can get past 50-60% trim in the #1 spot without ventilating you can probably benefit from raising the motor. I could almost get 75% so I knew #2 was pretty much guaranteed, thus skipped right to #3.

Can't remember the spacing on Yamaha but it's somewhere around 3/4" per hole, so not a lot. Also something to consider, prop diameter and motor shaft length - larger diameter prop may limit your height (mine is a 14.5" D) and the F150 comes in both 20" and 25" IIRC. But I think that trim test should be your best guide.

I say give it a try, but I'm reminded by another recent post about spending other people's money!

Sounds good! I can trim extensively and not see much difference in speed or bow lift at all so I plan to move to #2 hole. One of members said that a floor jack and block of wood between jack and skag is easy way to support engine while unbolting. Probably best to attach trailer to pickup so tongue doesn't shift or trailer roll. Cheap way to "get er done"........lol

 

[Potomacbassin’]

I’d be a little worried about supporting the motor from the top since you’ll have some shifting with the two lower bolts. I wanted to do the same thing but got cold feet, just didn’t want to screw something up with 3 months of boating left!

Good luck and take pictures to share!

 

[jhill]

I’d be a little worried about supporting the motor from the top since you’ll have some shifting with the two lower bolts. I wanted to do the same thing but got cold feet, just didn’t want to screw something up with 3 months of boating left!

Good luck and take pictures to share!

I figured that the two slotted bolts would only be loosened and never be totally removed so can't go too far wrong .........but then there is "murphy's law" so I will take safety precautions when attempting. Maybe add a rope with pulley from above for additional control while performing operation. Engine weighs like 500 # so should be easy to rig up from a beam, etc.