Acme 3087 and 3085

[dizzygti]

Anyone with experience with these props? 

3087 is 17.5x17.5 with 0.105 cup

3085 is 17.5x17 with 0.075 cup

Can someone explain cup?   Those cup specs look lower than most of the typical props mentioned on here.   

Currently running 3077 17x15.5 on M6'ed T250 at 1070 ft elevation, and only have 1.15" between prop and hull, so don't think I can go to an 18" diameter.   Looking to drop surfing rpms and raise top speed slightly.  Top speed is just the speed freak in me wanting more, but know that's not what these boats are for or that it even matters.   I do want to drop surf rpms though for noise reduction.   Usually surf around 11.5mph and ~3500 rpms depending on crew size.   Thanks in advance!

[justgary]

On 12/7/2023 at 10:50 AM, dizzygti said:

Can someone explain cup?

Cup is curving the trailing edge of the prop blades.  It adds effective pitch.

What RPM do you get with your prop at wide open throttle when you are fully rigged and loaded for surfing?  If you aren't getting near 5,000 RPM, adding pitch will lug the engine even worse.  Surfing and going fast are opposites with your boat, and you can't do both well at all with one prop.

[dizzygti]

14 minutes ago, justgary said:

Cup is curving the trailing edge of the prop blades.  It adds effective pitch.

What RPM do you get with your prop at wide open throttle when you are fully rigged and loaded for surfing?  If you aren't getting near 5,000 RPM, adding pitch will lug the engine even worse.  Surfing and going fast are opposites with your boat, and you can't do both well at all with one prop.

Thank you.  That 3087 with low cup looks like an interesting option then.  I want larger diameter and a less rpms while surfing,  the low cup would somewhat offset the jump in pitch from 15.5 to 17.5.   The boat has plenty of power,  but you can can it struggle more loaded obviously.   Will have to test max rpm when loaded.  

[Woodski]

A go to reference on props:

https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwi1k__B1IeDAxVhAq0GHXcKA9YYABAOGgJwdg&ae=2&gclid=CjwKCAiAg9urBhB_EiwAgw88mUeD-5OBvPy25v-S9Z-1L1wkHAUpyCkMlIMByOW-TRu5H-1bjAFHexoCmggQAvD_BwE&sph=&ohost=www.google.com&cid=CAES5wHg9od2kOeFQ51p3Sv5YN6Laha7iwHOf03ZCDaxV8FNKr9Kerl7gAlmNo5K7nPceth0vZCTb5fgDqQREIlfZ4IDiYTf_V4FV6-LEkhXomoUiBcqp4wGlGuuF_xksxwSnMEWFHyruCl-I6Uanx9fA72NsUWBRMZO1wqK57ZcTHeQzp0hQsol2OK3dzf3rk-wSO6-KfpumW2ncYjrmeu6wYEXrwRK4VuEOaqlB-1WQlSvYSaEmHWtQe3TjjNRFk_art9m0H459IfAuk7OWjqxCSDDD6zl1496l97aPUQOW5K9IdA_1j9xSIE&sig=AOD64_1C9hz12VPnjXKseZcLP_r0jZcxeg&ctype=5&q=&ved=2ahUKEwjcn_jB1IeDAxU_FTQIHYh0DIIQwg8oAHoECAQQDA&adurl=

[Stevo]

I have the 3085 as my back up prop on my 2022- 25lsv with LT4

I use the 2805 17x17- .105 cup as my primary everyday prop and is the perfect fit for where and how we use the boat. 
75% - surf loaded

15% - wakeboarding 

10% - tube (10% and falling. Thank god)

With the Lt4 the 3085 dropped my fully loaded surf RPMs into the 2300’s vs the 2085 where it’s in the 2500-2600 range

 

Edited December 11, 2023 by Stevo

[CaptainMorgan]

On 12/7/2023 at 11:50 AM, dizzygti said:

Anyone with experience with these props? 

3087 is 17.5x17.5 with 0.105 cup

3085 is 17.5x17 with 0.075 cup

Can someone explain cup?   Those cup specs look lower than most of the typical props mentioned on here.   

Currently running 3077 17x15.5 on M6'ed T250 at 1070 ft elevation, and only have 1.15" between prop and hull, so don't think I can go to an 18" diameter.   Looking to drop surfing rpms and raise top speed slightly.  Top speed is just the speed freak in me wanting more, but know that's not what these boats are for or that it even matters.   I do want to drop surf rpms though for noise reduction.   Usually surf around 11.5mph and ~3500 rpms depending on crew size.   Thanks in advance!

i can see how pitch will help with RPMs and speed, but what is the diameter increase supposed to do?

i went through similar desirements (A24 w/ 3077 but only have the 409 engine at sea level).  i tried a 17" prop (the 2969, has .150 pitch though).  saved maybe 200rpm surfing and added 1-2mph top end when unloaded (39mph vs 37.something).  if i hadn't been measuring those specs though, wouldn't have noticed much difference (wife and kids had no idea this experiment was happening under their noses).  The one thing i did notice was the couple mph during cruising (e.g. 25 became 27mph for same RPM), but couldn't get to redline fully loaded like @justgary mentioned (tops of 5000rpm if i was lucky vs 5500 target), and when surfing i noticed it was harder to get to/maintain speed (no quantifiable number, but felt more cavitation/struggle on launch and settling of paddlewheel speed 'seemed' to take longer).  if i was a wakeboarder, 20mph fully loaded would have been a struggle. 

for me, I decided its such a small difference, no reason to potentially lug the engine when loaded down, the noise difference was minimal, and the 'smoothness' of surfing is better with the 3077 as my boat is just barely strong enough to do the job.  Your M6 is more powerful and lower cup may be smoother during surf launching (folks rave about the 2805)...but just want to manage expectations that you're probably chasing a change of say 200rpm and 2mph for a likely cost of >$1k. 

Bottom line:  If you need a backup prop anyway, then i'm a huge fan of trying something different and no harm if it doesn't improve things as you're probably in a pretty good spot to begin with

 

[dizzygti]

On 12/11/2023 at 12:22 PM, CaptainMorgan said:

i can see how pitch will help with RPMs and speed, but what is the diameter increase supposed to do?

i went through similar desirements (A24 w/ 3077 but only have the 409 engine at sea level).  i tried a 17" prop (the 2969, has .150 pitch though).  saved maybe 200rpm surfing and added 1-2mph top end when unloaded (39mph vs 37.something).  if i hadn't been measuring those specs though, wouldn't have noticed much difference (wife and kids had no idea this experiment was happening under their noses).  The one thing i did notice was the couple mph during cruising (e.g. 25 became 27mph for same RPM), but couldn't get to redline fully loaded like @justgary mentioned (tops of 5000rpm if i was lucky vs 5500 target), and when surfing i noticed it was harder to get to/maintain speed (no quantifiable number, but felt more cavitation/struggle on launch and settling of paddlewheel speed 'seemed' to take longer).  if i was a wakeboarder, 20mph fully loaded would have been a struggle. 

for me, I decided its such a small difference, no reason to potentially lug the engine when loaded down, the noise difference was minimal, and the 'smoothness' of surfing is better with the 3077 as my boat is just barely strong enough to do the job.  Your M6 is more powerful and lower cup may be smoother during surf launching (folks rave about the 2805)...but just want to manage expectations that you're probably chasing a change of say 200rpm and 2mph for a likely cost of >$1k. 

Bottom line:  If you need a backup prop anyway, then i'm a huge fan of trying something different and no harm if it doesn't improve things as you're probably in a pretty good spot to begin with

 

Generic description about larger diameter from Wakemaker's Acme prop description:  "offers more surface area which means a more efficient transmission of power, higher fuel economy, and more consistent speeds."   Think of it like a ceiling fan or box fan: bigger diameter moves more air.   To me, the larger diameter just offsets some of the increase in pitch at lower rpms, aka more power to get on plane with the higher pitch.  I would wager that people rave about the 2805 but your lack of more noticeable results with the 2969 was the difference in cup:  2805 @ 0.105 vs 2969 @ 0.150.   The more aggressive cup made it more like a lower pitch effectively, so probably closer to a 16, not that different than the 3077.   I know the 2805 will do what I want, but I'm a gearhead and engineer, so enjoy the what if's and trying to optimize.   I realize I'm chasing incremental gains, but I do need a spare prop regardless.   Just have to decide on what flavor I want to try.   

Edited December 13, 2023 by dizzygti

[CaptainMorgan]

8 hours ago, dizzygti said:

Generic description about larger diameter from Wakemaker's Acme prop description:  "offers more surface area which means a more efficient transmission of power, higher fuel economy, and more consistent speeds."   Think of it like a ceiling fan or box fan: bigger diameter moves more air.   To me, the larger diameter just offsets some of the increase in pitch at lower rpms, aka more power to get on plane with the higher pitch.  I would wager that people rave about the 2805 but your lack of more noticeable results with the 2969 was the difference in cup:  2805 @ 0.105 vs 2969 @ 0.150.   The more aggressive cup made it more like a lower pitch effectively, so probably closer to a 16, not that different than the 3077.   I know the 2805 will do what I want, but I'm a gearhead and engineer, so enjoy the what if's and trying to optimize.   I realize I'm chasing incremental gains, but I do need a spare prop regardless.   Just have to decide on what flavor I want to try.   

makes sense, fun experiment since you need a spare anyway and TMC will certainly be curious about results (i'm an engineer so i took data on each prop and made graphs of each for fun, posted elsewhere on TMC).

i agree the cup difference in the 2969 is the main reason my results were the way they were, but i've always had in my head that extra cup acts like *more* pitch (google results say things like "If the cup is on the trailing edge, it effectively increases the pitch size").   The 2969 had same cup as 3077, so i was adding 10% more pitch without any other variables changing and my boat doesn't have the power for that. 

A couple years ago during my prop search i asked ACME about upgrading to 2805 vs 3077 and they basically shrugged that difference would be super small because the longer pitch of 2805 is partially offset by lower cup.  Hence i experimented by the 2969 purchase, and it'd work fine, but 3077 is my 95% solution so i called it good enough and started spending my money on foiling...  

[justgary]

Adding diameter does add blade area, which helps reduce slip.  Blade area also adds drag though, so it takes more power than a smaller diameter prop.  This is also why a four blade prop might give better hole shot than a three blade, but generally goes slower at top speed due to blade drag. Three things limit blade diameter on an inboard boat:

1. Clearance between the prop and the hull.
2. Total power available to turn the prop under a given load.
3. Tip speed of the prop at maximum RPM.

Changing the transmission gear ratio help with #2 and #3, but eventually any motor will run out of power available to turn bigger props.

For maximum pulling power at less than maximum RPM, go for a larger diameter prop with lower pitch, and possibly add a fourth blade.  For maximum speed at maximum RPM, go for a smaller diameter with higher pitch, and reduce the blades to the minimum you can get.  Two blades are not common for inboards, primarily because blade balance is much more important with two than three.  More blades tend to run with less vibration due to lower average pull per blade.  Yes, a one-blade prop would be most efficient in terms of drag, but balancing the thing is a real trick.

Smaller diameter and higher pitch have a limit also, since hole shot begins to suffer greatly as pitch goes up (and diameter goes down to limit required power).  Small racing boats typically use a two-step approach to gaining speed.  The first step involves intentionally cavitating the prop by flailing the water with high RPM and letting the boat slowly gain enough speed to plane out.  The second step can be a momentary throttle cut or a weight shift to stop the cavitation, then accelerating the boat to top speed.

[granddaddy55]

On 12/11/2023 at 8:45 AM, dizzygti said:

Thank you.  That 3087 with low cup looks like an interesting option then.  I want larger diameter and a less rpms while surfing,  the low cup would somewhat offset the jump in pitch from 15.5 to 17.5.   The boat has plenty of power,  but you can can it struggle more loaded obviously.   Will have to test max rpm when loaded.  

less rom’s surfing is actually lugging your motor bad snd can cause oil degradation because of more fuel blow by from it.  its much easier on your motor to move a 13k+ load while surfing with higher rpms.  your way its more frequent oil changes and worse for longterm life of your motor.  if you surf with light ballast and crew maybe not but what fun is that!?!?

Edited December 14, 2023 by granddaddy55

[dizzygti]

8 hours ago, granddaddy55 said:

less rpm’s surfing is actually lugging your motor bad 

That's an assumption and would need confirmation of the requested "load" from the ECU vs generated power.   You can tell when the engine is "lugging" and when it's smoothly making power based on NVH.   It's the same sensation you get when surfing and suddenly hitting shallow water.   When I said you can feel the motor struggle when more loaded, I more meant when done surfing and I throttle down to head home with the ballasts still mostly full and emptying.  Getting up to surf speed when fully loaded doesn't struggle at all with my T250/M6.   Like I said earlier, I need to confirm top speed when loaded and rpm to know if I have "power" to spare to shift the prop pitch like I want.  

Edited December 15, 2023 by dizzygti

[dizzygti]

Christmas Eve test completed,  on the water currently.   All ballasts full, only my wife and I, but boat will do 36+ mph at 5600rpms no problem when fully loaded (750 front pnp and 2x 850 rear pnps).  

Edited December 25, 2023 by dizzygti

[justgary]

21 hours ago, dizzygti said:

Christmas Eve test completed,  on the water currently.   All ballasts full, only my wife and I, but boat will do 36+ mph at 5600rpms no problem when fully loaded (950 front pnp and 2x 850 rear pnps).  

At 5600 it is probably rev limiting.  If that is the way you normally roll, you could add some pitch.  If you were missing 9 people, maybe don't add pitch.

[dizzygti]

42 minutes ago, justgary said:

At 5600 it is probably rev limiting.  If that is the way you normally roll, you could add some pitch.  If you were missing 9 people, maybe don't add pitch.

Yes, that's redline and max speed with the current prop.  With wedge at 5, all ballasts full, cruise set at 26mph, engine sits at 4800 rpms.  There's power to spare...  

 

Merry Christmas!

Edited December 25, 2023 by dizzygti

[CaptainMorgan]

22 hours ago, dizzygti said:

Christmas Eve test completed,  on the water currently.   All ballasts full, only my wife and I, but boat will do 36+ mph at 5600rpms no problem when fully loaded (950 front pnp and 2x 850 rear pnps).  

Nice, baseline complete (and super jealous you were boating on xmas eve, well done!)

Did Santa put a new one in your stocking?  Will be great to see the new data on that prop. 

[dizzygti]

23 minutes ago, CaptainMorgan said:

Nice, baseline complete (and super jealous you were boating on xmas eve, well done!)

Did Santa put a new one in your stocking?  Will be great to see the new data on that prop. 

Not yet, will order on Wednesday.

Air temp was low 60s and cloudy,  5-10 mph winds, water about 50, a 4/3 suit was all that I needed to get a good 40 min session, wife did the same!   Happy holidays indeed.