Supra 24V - 8.1/496 prop selection for Surfin', Wakin', Slalomin', AND Footin'

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08-14-2019, 03:04 PM
Hanso24V

Supra 24V - 8.1/496 prop selection for Surfin', Wakin', Slalomin', AND Footin'

Just picked up a 2006 SS 24V with Indmar 8.1. The stock ACME 497 13x17.5 is not impressive out of the hole and only turns 4800 rpm at 50 mph with an 800lb load. Thought the 8.1 could run better so called Supra, Indmar, Acme, Wakemakers, and Bakes to help make a new prop selection. Very long story very short....... not much knowledge out there on propping the 8.1. I got suggestions of 13x16, 14x15.5, and 14x14.25 from a flow chart based on usage or simply they said I can't surf and foot behind the same prop. Guys......that's why I bought the 8.1. 450hp, 525 lb ft of torque, and revs to 5400 rpm can do a lot. Thats 125hp, 175lb ft, and 600 more rpms than the 5.7 Assault motor. After much online reading about others' 8.1 driven prop experiments and significant calculation regarding pitch, diameter, cup, RPM, and finally slip percentage estimation, I made a choice. The ACME 1273, 14.5x14.25, .150 cup, arrives tomorrow and I will record RPM and MPH info on both props to share with the forum. The lower pitch pulls harder, the larger diameter moves more water, the increased cup controls high speed RPM. My calculations show the 1273 will run 48mph at 5200 rpm with a barefooting load and carry 3000lb surf ballast at 11mph easily for the surfers. Fingers crossed!
08-14-2019, 09:35 PM
MJHKnox

Good luck. Depending on your weight, how fast do you need to go to barefoot?

I've only seen 2-3 people in my life do this and they are 100% d-drive/ski boat purists.

48-50mph in a wake boat, yikes. She will be runnin in hard.

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08-15-2019, 05:11 PM
Turbinesurgeon

I have the same hull but I’m running the 340hp 350. I upgraded the factory prop to the Acme 1433. I didn’t even see your prop as an option on both the wakemakers or acme website. Anyways I can hit 40mph with an empty boat, calm day, and slight tailwind. I slalom skied once behind this boat. Not a good boat for that but I’m not much of a skier either. We mainly surf and the prop does great with nearly 4K in ballast and 6 people in the boat.

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08-16-2019, 01:55 PM
Hanso24V

Quote:

Originally Posted by Turbinesurgeon

I have the same hull but I’m running the 340hp 350. I upgraded the factory prop to the Acme 1433. I didn’t even see your prop as an option on both the wakemakers or acme website. Anyways I can hit 40mph with an empty boat, calm day, and slight tailwind. I slalom skied once behind this boat. Not a good boat for that but I’m not much of a skier either. We mainly surf and the prop does great with nearly 4K in ballast and 6 people in the boat.

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Glad to hear the 1433 is working well for you. The 1273 is very similar to the 1433 just larger diameter with more cup. It isn't on the flowcharts for either site because those are created for the 5.7 motors. I am assuming you're running about 4600 rpm at 40 mph? I will test the new prop tomorrow and see what the GPS says.
08-16-2019, 03:16 PM
Hanso24V

Quote:

Originally Posted by MJHKnox

Good luck. Depending on your weight, how fast do you need to go to barefoot?

I've only seen 2-3 people in my life do this and they are 100% d-drive/ski boat purists.

48-50mph in a wake boat, yikes. She will be runnin in hard.

Sent from my P00I using Tapatalk

I like to longline about 42 and on our inaugural run last week it went 50mph very smoothly. The 1273 is installed so tomorrow is test day and we'll see how the combo works.
08-18-2019, 12:49 AM
Turbinesurgeon

Quote:

Originally Posted by Hanso24V

Glad to hear the 1433 is working well for you. The 1273 is very similar to the 1433 just larger diameter with more cup. It isn't on the flowcharts for either site because those are created for the 5.7 motors. I am assuming you're running about 4600 rpm at 40 mph? I will test the new prop tomorrow and see what the GPS says.

5k rpm. I don’t run it at that rpm long. Just tested the new prop. I usually cruise between 30 to 35 mph.

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08-18-2019, 12:48 PM
Hanso24V

Quote:

Originally Posted by Turbinesurgeon

5k rpm. I don’t run it at that rpm long. Just tested the new prop. I usually cruise between 30 to 35 mph.

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The 1273 made the holeshot awesome and ran 46.5 mph on gps at 5000 rpm with an 800 lb. load. Pretty close to what I wanted, only 200 rpm short of ideal. Will probably run it until next Spring and then try a 1847. 1/2" smaller diameter on the 1847 may turn the extra revs to get to 48 mph. Just not sure its wise to spin a big block over 5000rpm for a couple more mph. What would you all do?
09-02-2019, 09:47 PM
Hanso24V

Surf update: Pulled surfers with 3000lbs of water and people ballast at 11.5 mph at only 2400 rpm. Easy up and ample throttle response fully loaded then dumped the water and passengers to go make a solo WOT run at 49mph on GPS. #veryhappySupraowner
09-02-2019, 11:52 PM
Turbinesurgeon

Wow. That would never happen with my 350

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09-03-2019, 09:19 AM
MJHKnox

That is flying. Good for you.

Yea, the old 350 knows it's place at low 40s. Actually, not even sure how fast she is at WOT and my prop selection, but not 49mph.
09-04-2019, 04:33 PM
Hanso24V

Buyers seem to shy away from the 8.1 because they're worried about fuel consumption but are buying the 450hp 6.2 and 550 hp supercharged 6.2 in the newer big boats. It takes a certain amount of fuel to create the power to push a 7500 lb load at 11 mph through the water so I don't understand how there can be a fuel consumption issue with high power motors over the 350. I bet the 350's do a great job in 22' and below but from what I've seen 23' and up need that extra 100 hp to move all that fibergalss.
09-04-2019, 08:36 PM
MJHKnox

Quote:

Originally Posted by Hanso24V

Buyers seem to shy away from the 8.1 because they're worried about fuel consumption but are buying the 450hp 6.2 and 550 hp supercharged 6.2 in the newer big boats. It takes a certain amount of fuel to create the power to push a 7500 lb load at 11 mph through the water so I don't understand how there can be a fuel consumption issue with high power motors over the 350. I bet the 350's do a great job in 22' and below but from what I've seen 23' and up need that extra 100 hp to move all that fibergalss.

Talking to techs that worked on the 8.1 and the 550s, they can be "temperamental".

For SC in 2020, now they moved to the new ratio of 1.76, they are hoping the west coast/high altitude buyers like the 460 motor with that combo.

Agree with you on the 350 motors in the 22' and below.

Those new Supras are pushing > 7.5K down the lake.
09-04-2019, 11:05 PM
Hanso24V

My 8.1 has a pretty noticable lope and a supercharger adds its own wrinkle so I could see where some issues could arise.

That deep ratio on the new, heavy boats makes a lot of sense. If they run a moderate pitch for low speed power with some heavy cupping to hold rpms down at higher speeds they could have a great compromise. If my V drive ever goes I'm definitely dropping from a 1.21 to 1.46 ratio like the Malibu's run. That will make more prop options possible.

Hoping for a couple more warm days here in WI to get in a few more lake hours before we pack it all up for the season.
09-06-2019, 09:15 AM
MJHKnox

That 8.1 and v-drive will probably keep on running and running.
09-09-2019, 02:55 PM
Hanso24V

Agreed! I plan on maintaining/using this rig for the next 20 years. Only 140 hrs. on it so far.