Prop help

[msher]

Hey all,
I've got a question about switching out to a more powerful prop pitch. Our Nautique, HEIR NAUT, is a 2001 Air Nautique (Sport) direct drive. The stock prop is a 13-16 OJ Legend. My issue is the boat is a little under powered with a 5.0 liter, 305 PCM power plant. I'll never go to small again!!!Particularly with a load of folks, the stock ballast and a sack in the stern locker. We wake board, surf (some) and ski a few times a year. Top speed is not an issue, power is. However I don’t want to risk damaging the engine with too much RPM. What is the best option?
Thanks, Msher
Mark Sherwin

[Rick]

If your loading up the boat and are looking for more hole shot I wold go with a 13 13 That will still give yoyu around 38 mph top end and alot better hole shot. I believe both ACME and OJ offer discounts for members You should call them and describe exactly what you want and they can ,make recommendations.. Good luck

[NautiqueJeff]

I'd suggest contacting Delta Props. They are a site sponsor, and can set you up with exactly what you need the first time. They also offer our members 20% off new ACME props, so that's quite a savings. They are great to deal with. Give Gary a call at 513-467-0601.

[msher]

Thanks Gentlemen,
I'll do my home work and make a decission. If I'm not mistaken the 13-13 is the same pitch that came on my 82, 2001. I never had hole shot or power issues with that.
Jeff,
FYI, I just placed an order with Nautique Skins for new seat bottom skins and another with nautiqueparts.com for a couple of pull up "Correct Craft" cleats. While I support my local CC dealer there is alot of great info on Planet Nautique, the sponsors have my support.
Thanks,
Mark

[Zigzag55k]

The quick answer is a 14 X 16 4 blade OJ or 612 Acme 3 blade. Disclaimers here call Acme to verify that is the right number. The Acme has incredible hole shot but is very loud and makes the boat growl like the old MC powerslot. The OJ is very quiet and smooth and will give you better hole shot than your 13 X 16. With torque or hole shot you are looking at prop column travel per revolution. The 13 X 13 is not a viable option. Hope this helps.

Mark Qualkinbush

[Mikeski]

Guys, There seems to be some misinformation here. Note the boat is a model year 2001 not a 2001 so the boat has a 1.23:1 gear reduction transmission so I WOULD NOT recommend a 13 x 13 prop. Also a 14x16 is harder to turn than a 13x16 so it will give you less holeshot, that prop would be going the wrong direction for what you are trying to do, (surprised to see this suggestion from you Mark).

As Jeff suggested, the best thing to do would be to contact Acme and talk directly to Bill Weeks or contact OJ and speak with Eric Johnson if you prefer to stick with OJ. I run an OJ on my slalom boat and a Acme on my wakeboard boat. Since I share ownership with another family on the slalom boat I prefer the OJ since it is much more likely to survive the striking of a stick in the water due to the thicker blades used on the OJ. On the wakeboard boat I need every ounce of power I can squeeze out of the motor so I use the Acme.

You might want consider reducing the diameter to 12.5, reducing the pitch to 15.5 or lower, or both. Also pay attention to the cup of the prop, if you have range in the upper rpm limit you might want to go with less cup. Make sure you buy from somewhere that will let you return it if you are not happy with the results.

Mike Jolley

[Mikeski]

Here is some contact info for you:
Bill Weeks
Acme Sales Engineer
1 888 661 2263

Eric Johnson
Johnson Propeller
800-359-9730

If you decide to go with OJ, I suggest you use one of their XMP CNC props.

[Zigzag55k]

Let me make this real clear. The 14 X 16 is a much quicker prop than a 13 X 16. I have several tests that prove this. The 13 X 16 only moves 13 per revolution and the boat is trying to be lifted here by a smaller column. The science is real clear in the propeller handbook written by David Gerr. The GT 40 with the 1.23 (gear reduction) turns the 14 better than the 13 (slippage & travel reasons). Easy way to look at things Diameter equals torque and pitch limits horsepower. Put the two together with proper column to weight ratio and you get the desired performance with minimal slip. CC used the 13 X 16 when the TSC 1 came out and used this prop across the board for all the direct drives. A 14 X 16 on a TSC 1 hull (Ski Nautique) will pull like a freight train in the course and have your arms begging for mercy thus a 13 X 16 is a better prop for that boat. He wants hole shot out of a bigger platform (Sport Nautique). We ran some tests at Fairland (our Ski lake) with Acme 3 blade and it was the quickest prop I've tested I just can't remember the number. I think 612. Like everyone has said Call Eric or Bill they will steer you in the right direction. I agree with Mikeski on durability with the OJs. I can usually get 4 rebuilds on an OJ and 2 or 3 on Acme.

Mark Qualkinbush

[Mikeski]

Hi Mark,

This is a good thread and I think we are entering into a healthy debate that will benefit everybody watching. Seems like you have some good empirical data from a different hull with a different powerplant. I have a some experience with different props on different direct drives but have experience with 8 different props on my Nautique 211. My previous boat was a 1995 Ski Nautique with a GT-40 turning a OJ 14x16 prop so I am very familiar with the stump pulling power from that combination. It pulled like a freight train even when I overloaded the boat with 2500lbs of ballast and human weight. In my opinion the torque of the GT-40 is unmatched by almost any other marine powerplant short of a python. A lightly loaded tournament direct drive powered by a GT-40 will jump from the water and build speed faster with the 14" prop because it has the torque to do so.

The situation described by msher is one of overload and underpower. The data obtained from a lightly loaded overpowered boat has little in common with msher's situation and should not apply. I would say that my 211 data has more in common with his overloaded and underpowered boat as described by msher. The power to weight ratio from the 275hp 5.0L motor in msher's boat is possibly more similar to the power to weight ratio of the 330hp motor in my SV211, versus the power to weight ratio described in Mark's test boat above with a 310hp high torque motor in a lighter boat. I have had 14.5", 13.5" and 13.25" diameter, 17.5", 16", and 14.25" pitch, and even different cupped props with similar diameter and pitch on my boat. I have on several occasions experienced a loaded boat that will not go beyond 10mph while trying to pull a wakeboarder from a deepwater with a few different props. I have experienced an unloaded boat that did not have enough power to pull a heavy slalom skier up on a deepwater start. This is just part of live with heavy liner hull powered by a GM powerplant with limited torque. In this instance the higher slip of the 13.25" diameter prop helps to get the motor into a the rpm range with a taller torque curve needed to push the barge through the water fast enough to plane. In my case the only time a larger diameter prop produced more holeshot is when the pitch was reduced by a full 1.75" per revolution (roughly 10%).

It would be very interesting to see the results if 1500lbs of ballast bags were added to the test boats Mark described above. I might be willing to place a nominal bet that the 13" diameter prop would out accelerate the 14" diameter prop. Any takers???

[Zigzag55k]

Mike, I will take your bet. Your own data posted in the thread prop diaries proves my point on hole and torque. The larger prop wins.

"7) Acme 1234 14.5x14.25 (standard cup) This prop is a good wakeboarding/wakesurfing prop. It is the strongest prop out of the hole when compared to all others. Unfortunately the top end is all the way down to 40mph with a light load and 38+/- for barefooting. It really pushes the motor into the higher rpm ranges for slalom skiing. i am not that comfortable pushing the motor that hard that often. The biggest unexpected realization from this prop was the golf ball sized water pellets it throws at skiers running 28off/34mph (that's me). Getting pelted in the midsection with these large water pellets in the midsection while skiing was no fun. Since I didn't want to start skiing with a cup, I traded this prop for an Acme 856 from a fellow Planet Nautiquer."

I'm going try to explain as a wheel. The given is a 1.23 reduction so now matter what prop is on the boat the wheel turns 1.23 times. Now that said would you rather have a small wheel and travel shorter distance per revolution or a larger wheel traveling a farther distance in the same time as we know it can only turn 1.23 times. All of the modern day engines will spin the larger prop easily including the 5.0 TBI 275 hp. This engine 5.0 falls short at WOT.

Mike my data was performed at Hawthorne ski lake with a very loaded 00 Air Nautique with both a Chevy motor and the Ford motor. We found the SN performed exactly the same when we tested at Fairland. We also ran tests running a 3 blade 14 X 16 against a 4 blade 13 X 16 on the river. The 3 blade was actually quicker. I lost a case of beer on that bet since I was convinced the 4 blade would win because I did not understand the constant vs. travel theory (1.23 reduction) vs. diameter travel. Hopefully I'm explaining this right.

Good luck guys.

Mark Q

[Mikeski]

Note my #7 prop is by far the flattest pitch in the group so it proves nothing from a comparison standpoint.

Comparing the 644 to the 536 is a head to head comparison of props with 16" pitch with different sized blades. They are nearly identical props, same pitch, same cup, only the 644 is 0.25" smaller diameter. The 644 is noticeably stronger out of the hole.

The 00 Air Nautique has both a Chevy and a Ford motor??? Must be some boat LOL.

I am an engineer and fully understand the fluid dynamics science behind propeller propulsion. You are ignoring the interaction between slip and torque in your analysis. If you chained the boat to the dock and allowed the motor to reach a full throttle stall I would expect to see the 13" prop turning higher rpms at a point where the motor is making more torque. This additional energy will be transferred to the chain and pull harder against the chain.

"All of the modern day engines will spin the larger prop easily including the 5.0 TBI 275 hp. This engine 5.0 falls short at WOT." I disagree with this statement and msher's post supports my position. You are giving these motors more credit than they deserve.

Beer is on ice...

[Zigzag55k]

Prop Help

Very simple, 1980 MC introduces 1.50 reduction (powerslot) with what motor. A Ford 351 240 hp non GT 40 heads. What prop? A 14 X 18. This drive train / slash engine combination set the standard and the basis of this package was to allow the bigger prop to move the boat farther forward in the 1.50 revolutions with the larger prop. It's not about the engines it's about the reduction package. 1987 Yamaha introduces a Pro V 150. This machine ran a 2 to 1 gear reduction allowing it to spin 14.25 X 19 making it quicker than the 430hp Python in similar weighted boats.

Your point about load and spinning up to rpms does apply with an impeller but not a propeller. An impeller runs at 100% load regardless of rpm. A propeller would burn up at 100 % load due to pressure created. The point about getting two props spinning is mute because the smaller prop would never achieve 100 % load. The propeller column of the larger prop would win given same engine packages and drive train (that being a 2500 to 3500 lb boat with a 1.23 reduction). Why it would hook up quicker and run in the mid 80% effeciency range on slip vs. the smaller column running at take off of 70% effeciency slip range. Neither prop would ever achieve a 100% load.

I want to add something in this thread. I'm driving home the point of diameter equals torque. Boat engineers have formulas they use as to what prop supports there platform best. Many variables go into this such as weight, strut angle, engine, transmission, etc. The boats we are talking about relative to the inboard industry will run on 12'' to 14'' columns. Lighter weight boats such as old Mustangs / Small Martinique’s will run on 12'' columns. Heavier boats will run on 14'' columns. Almost all 1 to 1 trannies will run on 13'' columns. Most gear reduction boats will run on 14'' columns. Now here comes the complicated part a 14'' is not really a 14'' prop. You actually need a dial gauge like prop shops use to measure what true diameter is. Take a 422 Acme 12.50 X 15.50 vs. an OJ 13 X 16. Then look at the two side by side. Surprise which one looks bigger. OJ runs a progressive pitch thus optical illusion can come into play. Many variables come into play when looking at props. Mike brings up some good points. A 15'' prop by theory should create more torque. It won't and the formulas will prove failure.

I'm not explaining this clear. It sounds like you desire knowledge and like formulas and principles. Order a copy of the Propeller Handbook written by David Gerr. This man is the guru of the marine industry. The book was a hard read for me and it required a calculator and a lot of scratch paper. He has another book out called Hulls Nautical Myths and Theories. This is a great read too.

Come on warm weather. I want to ski and then drink Mike’s beer Heck I will buy the beer as long we get to ski.

[msher]

WOW!!! Cool debate,
Sorry not to respond sooner, I've been driving all over Central Texas this week, as usual. Interesting discussion… It just so happens that I dropped off the original OJ prop at Nettles in Austin Monday. Unfortunately I hit something submerged last time out. The salesman recommended an ACME prop. Since I was supposed to pick it up today, I didn’t note the specs for his recommendation. I thought it said 12.5-15.5. Since he isn’t charging me to straighten the minor bend, I will support the local guy in this case. Also, he told me I could purchase his recommendation, take it, try it and exchange it if it wouldn’t do the trick. I’ll keep you posted once I install my choice.
Thanks,
Mark

[Mikeski]

Glad you enjoyed the debate. Hmmm, 12.5 is a pretty slim prop, not sure I would go that slim? Might want to try a 13x15.5 or 13.5 x 15.5 before going below a 13" diameter prop, I am sure Mark and I agree on this point. Small changes in diameter make a big difference, don't go too extreme. Best advice I posted was probably the suggestion to buy from a place where you can trade it if you don't like it. If you were closer I would let you try my 13 x 15.5 prop (1 1/8" shaft).

[tski97]

I could be wrong but the stock prop on the non 200 direct drives has been the 422 that is 12.5 x15.5. Why would that not be a good choice?