Props to address Cutwater performance

[Rocky Lou]

For those who haven't seen it already there is an excellent thread on PowerTech SCE/Modified props: https://www.tugnuts.com/threads/r27-ob-propeller-testing-results-are-in.24353/. You will find a great of deal of data showing significantly improved performance for R25/27 single Yamaha engines.

I've been quite happy with my Cutwater C302c LE that I bought new in 2019 with a few big exceptions. The performance, as I compared to other boats of similar size and weight was terrible with stern drag being a key factor, particularly with my model that has a heavy generator located aft. The chart below, from Boating Mag., is consistent with the kind of performance that I was getting. In particular, at 3500 RPM, I got a paltry 16 MPH. Props were: Twin F300’s - Saltwater Series II - 19-TL, 15.25.



So, for the past few years, I've been trying to improve performance. I got a quick win, albeit small, from adding drop fins that BB has advocated. I recently removed my Lenco trim tabs, that were aging and the well used drop fins had fallen off, with new 12x24 inch Bennett Trim Tabs that have drop fins one piece design. Again, they are worth having, but, do very little to help performance.

I investigated other props, notably spending two years testing Sharrow, then, moving onto PowerTech. I am currently running PowerTech OFS5, 17 pitch that provide considerable stern lift.

——————————————————————————————
Here is what I noted yesterday running the PowerTech 5 blade props:

• RPM, MPH, GPH
• 1000, 6 2.1
• 1500, 8 1.6
• 2000,10 1.2
• 2500, 12 0.7 to 0.9
• 3000, 16 0.9 tabs deployed
• 3500, 24 0.9 to 1.2
• 4000, 30 0.9 to 1.2
• 4500, 35 0.9
• 5000, 41, 0.7
• 5400WOT 44, 0.7

My observations:

• Getting on plane happened at much lower RPM
• Mid range performance improved 25-30%
• Trim Tabs need to be put to full down position to maintain control (this is normal) and tilt/trim was full down and not touched

Overall, I think we have had some success, however, I would expect that the high end to be, at minimum, 5500 RPM, up to 6000 RPM.

Based on the SCE/Modified post, I installed two props recently.
Unfortunately, the first trial run was a quick trip. The 14 inch props had no where near the much needed stern lift that the current OFS5 props
have and the mid range results were much worse.

Some of the key comparisons:
3500 RPM: SCE: 19 MPH, .9 MPG vs. OFS5: 24 MPH .9 to 1.2 MPG
4000 RPM: SCE: 26 MPH, .9 MPG vs. OFS5: 30 MPh, .9 to 1.2 MPG

The one area of improvement was WOT where I could get up to 5800 RPM with SCE and 44 MPH.

Speaking with PowerTech, they advised the the 'modification' that is their Patent Pending extension tubes (well described by Submariner) could be added to my OFS5s and will add some stern lift. I then agreed to test another set of OFS5 16 pitch with extensions to see if I can maintain the mid range performance and get the top end back to the normal operating range. While I was prepared to 'declare victory' with the OFS5 17s, since I rarely need top speed, they wanted to give it one more shot that I'll report once completed. In all, PowerTech is a great company to work with, have products that significantly improve performance over Yamaha SS2s, and only cost about $1K per copy.

 

[Submariner]

——————————————————————————————
Here is what I noted yesterday running the PowerTech 5 blade props:

• RPM, MPH, GPH
• 1000, 6 2.1
• 1500, 8 1.6
• 2000,10 1.2
• 2500, 12 0.7 to 0.9
• 3000, 16 0.9 tabs deployed
• 3500, 24 0.9 to 1.2
• 4000, 30 0.9 to 1.2
• 4500, 35 0.9
• 5000, 41, 0.7
• 5400WOT 44, 0.7

If you can publish data like the above that includes RPM, Speed and GPH, I'll create you a cool datasheet/graph. It looks like RPM, MPH and MPG you posted.
The Yamaha gauge isn't very accurate on mpg calculations and the spreadsheet calculates mpg from mph and gph.

If you've got data like the above, for the other prop's you've tested, post them as well and I'll put together a data sheets to make comparison easier to see.

 

[Rocky Lou]

Sounds good, I agree that there's a lot of guesswork with the Yamaha readings...mine are 0.4. 0.7, 0.9., 1.2, etc. Half the time you are looking at it saying and calculating that's way off. That is why I listed some readings as 0.9/1.2MPG, it was constantly changing with water conditions.

My hope right now is that the extensions will make up for the difference between 17 and 16 pitch. Did you get noticeable stern lift from adding extensions?

 

[Submariner]

Sounds good, I agree that there's a lot of guesswork with the Yamaha readings...mine are 0.4. 0.7, 0.9., 1.2, etc. Half the time you are looking at it saying and calculating that's way off. That is why I listed some readings as 0.9/1.2MPG, it was constantly changing with water conditions.

My hope right now is that the extensions will make up for the difference between 17 and 16 pitch. Did you get noticeable stern lift from adding extensions?

The exhaust tubes significantly increased lift and mpg in the mid range (3000-4000 rpm). Once I'm going faster than 20mph (>4000 RPM), the prop functions as normal and the tube makes little difference. Last weekend I was crossing Puget Sound doing 15 mph at 1.7mpg, then increased speed to 28mph and was still at 1.7mpg. The Yamaha display for me only shows .9, 1.2, 1.4, 1.6, 1.9, 2.1mpg. I always do the math (mph/gph) to get mpg.

What I did on the SCE5 prop, PowerTech shipped it to me. Then I lost the exhaust tube while testing the OFS4. So I had the SCE5 with no exhaust diffuser or extention or anything. I called it "stubby" as it was a 5 blade prop with just the castle nut sticking out the back. I ran it to WOT to at least see if it hit 5500-6000 RPM. Since it did, I asked PowerTech to make another exhaust tube to test on the SCE5. It sifnificantly improved the performance in the midrange adding the exhaust tube.

I never published this, as it's not a scenario that anyone would want to run a prop. But I'll share it here. This is the datasheet I did on the SCE5 stubby, to compare to my previous post, illustrating the difference the exhaust tube makes.

 

[cliffm]

With twins. You're a candidate to run Mercury Enertia ECO's in 16.5 or 17P. They are 16" diameter and the MPG winners in numerous scenarios, per Ken at PropGods.com. We were unable to run on our single F300 R27 as we required lower pitch, so we went with Turning Point Mach3 OS (very similar to Enertia ECO) in 13P providing 600-6000rpm range.

 

[Rocky Lou]

With twins. You're a candidate to run Mercury Enertia ECO's in 16.5 or 17P. They are 16" diameter and the MPG winners in numerous scenarios, per Ken at PropGods.com. We were unable to run on our single F300 R27 as we required lower pitch, so we went with Turning Point Mach3 OS (very similar to Enertia ECO) in 13P providing 600-6000rpm range.

Interesting, I talked a while back with Ken and he recommended PowerTech OFS4s or OFS5s for the needed stern lift. Given that I've gone from cruising at 30 MPH, and getting 0.7MPG with SS2s, to 1.2 MPG with PT OFS5s, I'm overall happy with the results. I've got one more trial, as indicated, with a 16 pitch prop and extended exhaust tubes, then I'm definitely 'putting a fork in it'.

 

[cliffm]

I wanted to add my experience with Turning Point Props which has been very positive. The problem, as noted by Ken & Phil, is they run "heavy" on the pitch due to cupping, meaning their advertised 15P props perform very close to 16P or 16.5P. This is great for grip and low slip numbers, but challenging when they only offer in 2P steps and trying to dial in RPM band applications. We had ran a TP Mach4 Express Dual-Geometry Prop in 15P, but our WOT rpm was below 5400rpm, though mid range MPG was fantastic! We then tried a PowerTech OFS4 in a 14P but the slip numbers were very high and the MPH was reduced, even after having it reworked for for additional cup, so we sold it.

At this point I would also note that "stock" PT props hub lengths are shorter than TP prop hubs. TP Mach4 was 1.0 longer that PT OFS4. TP Mach3 OS is 8" long and 1.5" longer than PT LFS3. Turning point tends to follow Mercury Marine in prop designs and offers prop models "mimicking" REV4, Bravo and Enertia series.

That lead us back to Turning Point and our current Mach3 OS in 13P (as we felt the 15P would act to high) I find the 5-blade application intriguing, but Hodges Marine pricing for Turning Point props makes it a super attractive price point for sales. I'm also a fan of the TP 805F prop hubs, as they act very similar to Yamaha SDS prop hubs in operation.

I'd be very curious if you could run the Mach3 OS in 17P for the mileage improvement? or the 15P version for quicker up-on-plane performance.

 

[Ed604]

Hi Rocky Lou,
I was wondering if you also notice better thrust in reverse too? Does "splitting the sticks" now work better to do slow maneuvers? I always thought that the issue was because the twin motors were placed so close together that twisting the boat was not very effective using just the engines. Can you get the stern to shift with just the torque of one engine?
I am wondering if these things are now more effective with the increased grip of the props?

Currently for little twisting and side shifting, I just use the thrusters but in even moderate wind days this isn't the best, as the thrusters (especially the stern) quickly become overpowered by even light wind.

lastly, would you say that you are now able to stay "up" and on plane, at lower speeds such as 15knots or lower? I need to be moving pretty quick to get the benefit of being higher out of the water. Some days this leads to some rather large bangs as I try to get the balance right for conditions.

BTW, I very much appreciate you sharing your journey in exploring different props to address certain issues that the boats have. I have been watching you and Martin very closely with interest.
thanks,
Ed604

 

[Rocky Lou]

Hi Rocky Lou,
I was wondering if you also notice better thrust in reverse too? Does "splitting the sticks" now work better to do slow maneuvers? I always thought that the issue was because the twin motors were placed so close together that twisting the boat was not very effective using just the engines. Can you get the stern to shift with just the torque of one engine?
I am wondering if these things are now more effective with the increased grip of the props?

Currently for little twisting and side shifting, I just use the thrusters but in even moderate wind days this isn't the best, as the thrusters (especially the stern) quickly become overpowered by even light wind.

lastly, would you say that you are now able to stay "up" and on plane, at lower speeds such as 15knots or lower? I need to be moving pretty quick to get the benefit of being higher out of the water. Some days this leads to some rather large bangs as I try to get the balance right for conditions.

BTW, I very much appreciate you sharing your journey in exploring different props to address certain issues that the boats have. I have been watching you and Martin very closely with interest.
thanks,
Ed604

Hi Ed,
You are correct that the close placement of the engines makes them far less effective for making turns by splitting the sticks. it's still a primary way for me to enter and leave my slip at the harbor, along with bow/stern thrusters. I can't say with certainty there is improvement and I don't know a way to measure any changes from the props. However, it is an effective way to turn my boat and i can turn with only one engine under light to moderate wind and currents. Also, I'm guessing that a trained driver would rev engines much higher than I do as I've seen that done on tenders for cruise ships in heavy wind/seas. I'm not willing to take that chance since a small ding is much easier to repair than what might happen if you make a mistake under high RPMs.

You can see at what speed I start planing from these RPMs:

• 2500, 12 0.7 to 0.9
• 3000, 16 0.9 tabs deployed...planing
• 3500, 24 0.9 to 1.2
• 4000, 30 0.9 to 1.2

When I was running SS2s, I was lucky to start planing at 3500 RPM and would sometimes only be doing 16 MPH and 0.4 to 0.7 MPG...just awful. The chart above from Boating Mag. is even worse. They reported needing to be traveling at 4500 RPMs for max. efficiency....good luck doing that in the Pacific Ocean on many days.

It's indeed been a journey for me to improve efficiency. While I love the boat, I considered dumping it a few times. A friend, Dave, and I collaborated a while back. Dave did sell his Cutwater similar to mine as he could not stand the inefficiency and was also promised help from the factory, which didn't happen. I recently reached out to him and told him that I had solved, to my standards, the efficiency issue and he was pleased to hear. He'd just returned from a Great Loop trip with the boat he'd bought to replace the Cutwater. As I'm now in the 'Everyday is Saturday Club', I have time for projects like this and hope that the results are beneficial to other Tugnutters.

As stated, I have one more step since I returned the SCE5s (keeping the extension tubes) and will receive OFS5 16 pitch (instead of the current OFS5 17 pitch). It's another testament to PowerTech that they offered me an additional exchange after I said I was generally pleased with the results.

 

[Submariner]

I'm also a fan of the TP 805F prop hubs, as they act very similar to Yamaha SDS prop hubs in operation.

I found the Yamaha hub to be clunky compared to the PowerTech's hub. It's another reason I prefer the PowerTech over the Yamaha prop.

 

[Ed604]

Hi Ed,
You are correct that the close placement of the engines makes them far less effective for making turns by splitting the sticks. it's still a primary way for me to enter and leave my slip at the harbor, along with bow/stern thrusters. I can't say with certainty there is improvement and I don't know a way to measure any changes from the props. However, it is an effective way to turn my boat and i can turn with only one engine under light to moderate wind and currents. Also, I'm guessing that a trained driver would rev engines much higher than I do as I've seen that done on tenders for cruise ships in heavy wind/seas. I'm not willing to take that chance since a small ding is much easier to repair than what might happen if you make a mistake under high RPMs.

You can see at what speed I start planing from these RPMs:

• 2500, 12 0.7 to 0.9
• 3000, 16 0.9 tabs deployed...planing
• 3500, 24 0.9 to 1.2
• 4000, 30 0.9 to 1.2

When I was running SS2s, I was lucky to start planing at 3500 RPM and would sometimes only be doing 16 MPH and 0.4 to 0.7 MPG...just awful. The chart above from Boating Mag. is even worse. They reported needing to be traveling at 4500 RPMs for max. efficiency....good luck doing that in the Pacific Ocean on many days.

It's indeed been a journey for me to improve efficiency. While I love the boat, I considered dumping it a few times. A friend, Dave, and I collaborated a while back. Dave did sell his Cutwater similar to mine as he could not stand the inefficiency and was also promised help from the factory, which didn't happen. I recently reached out to him and told him that I had solved, to my standards, the efficiency issue and he was pleased to hear. He'd just returned from a Great Loop trip with the boat he'd bought to replace the Cutwater. As I'm now in the 'Everyday is Saturday Club', I have time for projects like this and hope that the results are beneficial to other Tugnutters.

As stated, I have one more step since I returned the SCE5s (keeping the extension tubes) and will receive OFS5 16 pitch (instead of the current OFS5 17 pitch). It's another testament to PowerTech that they offered me an additional exchange after I said I was generally pleased with the results.

Thanks Rocky Lou,
That is much slower on plane. That would be a big difference in the sloppy stuff, I also imagine the bow angle will be a bit lower in the water too having more lift, so that the bow entry angle is as sharp as possible vs, hitting the wave further back in the hull.
I will look for what you arrive at after this last version that you will be testing.
kind regards,
Ed604

 

[Ed604]

I found the Yamaha hub to be clunky compared to the PowerTech's hub. It's another reason I prefer the PowerTech over the Yamaha prop.

Martin, I also wanted to specifically thank you as well for all that you do and share! Your research is going to be a great option for may people.
Also, I really enjoyed your trip report last year!
great stuff!
Ed604

 

[Submariner]

Martin, I also wanted to specifically thank you as well for all that you do and share! Your research is going to be a great option for may people.
Also, I really enjoyed your trip report last year!
great stuff!
Ed604

You're welcome! It's fun. I enjoy all this prop testing stuff. Well, and electrical, and solar, and fishing, and, and and... 🙂

My last boat (a Mercruiser 5.0L MPI, 260HP with an Alpha 1 stern drive on a 22' bowrider/wakeboard boat) came with a 3 blade aluminum prop. My father, retired USCG of 26 years, on a clear blue skies, no wind, day, on Moses lake, ran my brand new boat aground, on Fathers Day! What do you do when your salty dog father runs your brand new boat aground and chews the prop up, on Fathers day?!?! Easy, I let the dealer sell me a high-five stainless prop! (and gave my Dad a bent-prop award! ha!). That 22' boat was an entirely different boat with that High-Five on. It never saw that 3 blade prop again.

It's amazing what the right prop on the boat can do for performance.

 

[Rocky Lou]

The results are in:
PowerTech: OFS5 blade 17 inch

• RPM, MPH, GPH
• 1000, 6 2.1
• 1500, 8 1.6
• 2000,10 1.2
• 2500, 12 0.7 to 0.9
• 3000, 16 0.9 tabs deployed
• 3500, 24 0.9 to 1.2
• 4000, 30 0.9 to 1.2
• 4500, 35 0.9
• 5000, 41, 0.7
• 5400WOT 44, 0.7

PowerTech: 5 blade 16 inch with EXT.

• 1000; 6, 2.1
• 1500; 8, 1.9
• 2000; 10; 1.2
• 2500; 11; 0.7
• 2500 tabs; 13, 0.9
• 3000; 18; 0.9
• 3000 tabs; 20; 1.2
• 3500 tabs; 27; 1.2
• 4000 tabs; 33 1.2
• 4500 tabs; 38 0.9
• 5000 tabs; 42, 0.9
• WOT tabs; 5400/5500; 47; 0.7

As I said to Marcus, when we spoke yesterday, I experienced the, “it feels like a new boat” phenomenon. If I can cruise at ~30MPH and get 1.2 GPH, I believe that is in line with my brother’s GW 330 and other boats of similar size, power and weight. Hence, it’s time to declare Victory and share these results with PowerTech and my fellow Cutwater owners via Tugnuts.com.

 

[Mike and Sarah]

Rocky
Thanks for all the hard work. We get our Solara 310 SB in less than 2 weeks. We won’t have time to try props before be head out on 750 mile trip but we will record our info and be excited to try the props you have on your c302.

 

[Submariner]

@Rocky Lou Those prop's look great on your boat!! 🙂

 

[Rocky Lou]

@Rocky Lou Those prop's look great on your boat!! 🙂

Thanks, I see the 'beauty' as well, given the work we've put in. The most stressful part of prop testing for me was changing out the Sharrow props in the water. I put a rope through the prop loop, just in case, to avoid losing a $5K item. I'm NAUI certified, but, that was in '72 and the only dives I do these days are in warm tropical waters.

 

[Rocky Lou]

Rocky
Thanks for all the hard work. We get our Solara 310 SB in less than 2 weeks. We won’t have time to try props before be head out on 750 mile trip but we will record our info and be excited to try the props you have on your c302.

Have a great trip! It will be interesting to see how the Solara results compare. The hulls appear similar...do you know if they are the same as Cutwater?

 

[Mike and Sarah]

Have a great trip! It will be interesting to see how the Solara results compare. The hulls appear similar...do you know if they are the same as Cutwater?

My understanding is the 310 hulls are the same as 288 hulls.

 

[Jcat2010]

Good to see the power techs are working out great for other models. One note about the "fear" of changing a prop while in the water......I use a 4 ft diameter inflatable kiddie pool, with three sidewalk tubes. Slide it up under the raised lower unit, anything that falls falls into the bottom. I even use it to periodically check the shaft seal for leakage. If only I could figure out how to change the lower unit oil using it.