3081 or 3087 G23 with H6 stock ballast

[greggmck]

At some point increasing the lugging of the engine is going to increase fuel burn. I might consider that switch if I thought my engine could handle it. I do some boating at 3600 feet and getting to plane at wakeboard speeds is a noticeable effort. I am anxious to hear your results, and hope they are good!

I am surprised anyone is complaining about noise. Compared to every other boat I have been in, the G is the quietest of them all.

If you get some problems with increased listing, it could be pretty easily offset with a ballast adjustment. With your presets available, you would only have to do it once.

There have been a few on the forums concerned about the noise of the boat. But I agree. Compared to every other boat I've surfed (Centurion, Supra, Tige, Supreme) the G23 is one of the quietest. But a significant increase in the list would be a deal killer for me. If that happens I will give the 17 x 18 a try. We are a family of competitive surfers. I already have 900lbs of lead in the boat with 600lbs on the port side to balance the wave to be nearly symmetrical with full ballast. In competition one has to do quick transfers to each side and perform tricks riding heel side. This becomes problematic if the starboard wave it is substantially different than the port side. I cant add additional lead on the port side or take lead off of the starboard side without risking imbalance issues with my lift, also causing greater lean in the boat when we are not surfing. The only option would be to reduce the water ballast on the starboard side and that would need to be substantial to offset any significant list, which could meaningfully change the wave on both sides.

[nyryan2001]

At some point increasing the lugging of the engine is going to increase fuel burn. I might consider that switch if I thought my engine could handle it. I do some boating at 3600 feet and getting to plane at wakeboard speeds is a noticeable effort. I am anxious to hear your results, and hope they are good!

I am surprised anyone is complaining about noise. Compared to every other boat I have been in, the G is the quietest of them all.

If you get some problems with increased listing, it could be pretty easily offset with a ballast adjustment. With your presets available, you would only have to do it once.

Tall, we’ve talked about this quite a bit.

fuel burn is the same no matter the speed for a given RPM:

2700 rpm 11.8 Mph with 5000lbs ballast = XX GPH = 2700rpms at 24mph no ballast

Rpms provide YY level of thrust regardless of speed vs weight and friction

theres no such thing as and easy 2700rpms and a hard 2700rpms, they are all equal pushing YY thrust

entirely different than your truck with no prop slip.

[ST3]

I spent a few days last week speaking to Jim at ACME. He was pretty certain that the 17.5X17.5 (3087) was the best prop for a moderately loaded G23 H6DI if I was interested in improving noise and fuel performance for surfing. We surf exclusively (sea level). We have an additional 900lbs of lead ballast and 3-5 people in the boat. With the stock prop we achieve 3450 RPM at 11.5mph. Our fuel burn is 6.7gal/hr over the past 25 hours.

I received the 8087 prop today. I will install it this weekend and report the RPM we achieve while surfing under identical conditions as the stock 17"x17". It will take me a few weeks to record an accurate fuel burn. I also plan to use a sound pressure meter to record engine noise before and after the prop switch.

The good thing about going straight to ACME is that they offer a 30 day trial on the prop. If this one doesn't work out I can swap it out for a different pitch/diameter to achieve the performance I am after.

Sent from my SM-G950U using PLT Nautique mobile app

This is a worthy experiment no matter what. Two items can be measured fairly accurately = SPL and RPM. The other factors are a bit tougher and more subjective. Please do keep us posted and provide as much data as you can including where you place your SPL meter, what kind of fuel was used, conditions on the lake, ballast (including human ballast). Thank you for sharing. !!!

[Tallredrider]

Tall, we’ve talked about this quite a bit.

fuel burn is the same no matter the speed for a given RPM:

2700 rpm 11.8 Mph with 5000lbs ballast = XX GPH = 2700rpms at 24mph no ballast

Rpms provide YY level of thrust regardless of speed vs weight and friction

theres no such thing as and easy 2700rpms and a hard 2700rpms, they are all equal pushing YY thrust

entirely different than your truck with no prop slip.

The prop does not have an infinite amount of slip, however. 2700 RPM lugged down barely up to speed with the throttle at 100% is going to burn more fuel than 2700 RPM at an easy cruise 1/3 throttle. Wouldn't you agree? To take it 1 step further, keep the boat in neutral and see how much throttle it takes to get to 2700 RPM. If the OP puts too much prop on, his fuel economy will go down struggling to get to speed.

[greggmck]

The prop does not have an infinite amount of slip, however. 2700 RPM lugged down barely up to speed with the throttle at 100% is going to burn more fuel than 2700 RPM at an easy cruise 1/3 throttle. Wouldn't you agree? To take it 1 step further, keep the boat in neutral and see how much throttle it takes to get to 2700 RPM. If the OP puts too much prop on, his fuel economy will go down struggling to get to speed.

This is not the way the fuel computer of the H6DI or any fuel injected engine works. If the engine is only able to run at 2700RPM it will not consume infinite fuel when the throttle is advanced. The computer will provide the fuel air mixture volume appropriate to the RPM of the engine. Each piston has a fixed volume. The total volume of air and fuel consumed in any unit of time is the volume of all pistons multiplied by the RPM at that given period. If the engine is unable to turn greater RPM it will not continue to dump fuel into the engine.

[greggmck]

This is a worthy experiment no matter what. Two items can be measured fairly accurately = SPL and RPM. The other factors are a bit tougher and more subjective. Please do keep us posted and provide as much data as you can including where you place your SPL meter, what kind of fuel was used, conditions on the lake, ballast (including human ballast). Thank you for sharing. !!!

I discussed this with Jim at ACME and agreed to provide the data he was interested in for this prop comparison. We concluded that I would measure the SPL at the drivers seat. If you have other locations of interest I can easily add them. Hull list can be accurately measured with an angle gauge set on a horizontal surface of the boat. I was expecting to measure list angle on the transom walk thru. Any significant change in list angle will also change the wave. We have over 500 hours surfing G23s and we know our wave very well. I expect to video the wave before and after the prop change to see if it has changed shape. I hope to get some smooth water this weekend to do the measurements.

[ST3]

I discussed this with Jim at ACME and agreed to provide the data he was interested in for this prop comparison. We concluded that I would measure the SPL at the drivers seat. If you have other locations of interest I can easily add them. Hull list can be accurately measured with an angle gauge set on a horizontal surface of the boat. I was expecting to measure list angle on the transom walk thru. Any significant change in list angle will also change the wave. We have over 500 hours surfing G23s and we know our wave very well. I expect to video the wave before and after the prop change to see if it has changed shape. I hope to get some smooth water this weekend to do the measurements.

For the SPL meter I would think either port or starboard front seats out of the wind...so likely low on the seat. Thanks again for sharing the data.

[greggmck]

Boat 2018 G23 H6DI
Conditions: Sea level. Air temp: 73 degrees. Water temp: 68 degrees.
Four persons including driver: Two Adults, Two teenagers
Total people weight 550 lbs. – All sitting on surf side (except driver on Goofy).
Fuel - Full to 80% for all measurements

Lead ballast – total 900lbs.
Port side: 200lbs rear locker, 200lbs middle seat, 200lbs bow.
Starboard side: 100lbs rear locker, 100lbs middle seat, 100lbs bow.


Noticeable Changes:

Dead slow is 1.5mph faster - Was 3 mph now is 4.5 mph

Boat seams quieter while surfing behind the boat. I can hear the music more clearly.

Surf wave is very clean and identical with both props.

Surf List angle: Port side is 1-2 degrees, Starboard side 4-5 degrees (identical for both props)

The boat accelerates slightly more slowly. But it does not seem to struggle. I ran up to 28MPH with full ballast and it did not have any problems. In summary, I am very satisfied with the propeller and would recommend. But I would NOT suggest going to a steeper pitch/larger prop with the H6DI. I would not want to put any more load on the engine. I need a few weeks to accurately measure fuel burn.

[greggmck]

Update. Fuel burn is .6 Gal/hour greater with the 17 1/2 x 17 1/2 compared to stock 17 x 17. Not what I want or expected.

[GMLIII]

Update. Fuel burn is .6 Gal/hour greater with the 17 1/2 x 17 1/2 compared to stock 17 x 17. Not what I want or expected.

Very good detailed info. Thanks for sharing

[Tallredrider]

Update. Fuel burn is .6 Gal/hour greater with the 17 1/2 x 17 1/2 compared to stock 17 x 17. Not what I want or expected.

I know I just took an intellectual beatdown for mentioning this might happen, but given the results, I would like someone to explain again why my truck pulling the boat gets significantly less MPG at the same RPM as I do when not towing. I know the explanation made some sense, but I now have renewed doubts. (OK, it wasn't a beatdown, they were very nice about saying that it was impossible to get lower mileage with lower RPM in a boat).

I am betting that the 17.5 X 17.5 is lugging the engine, even though it works. greggmck , did you by chance open it up full throttle and see if you can still reach the rev limiter? The guys at ACME suggest you are overpropped if you can't get the RPM's all the way to the top.

[RDT-G23]

I know I just took an intellectual beatdown for mentioning this might happen, but given the results, I would like someone to explain again why my truck pulling the boat gets significantly less MPG at the same RPM as I do when not towing. I know the explanation made some sense, but I now have renewed doubts. (OK, it wasn't a beatdown, they were very nice about saying that it was impossible to get lower mileage with lower RPM in a boat).

I am betting that the 17.5 X 17.5 is lugging the engine, even though it works. greggmck , did you by chance open it up full throttle and see if you can still reach the rev limiter? The guys at ACME suggest you are overpropped if you can't get the RPM's all the way to the top.

I have the same prop that I’m about to install this week, but no additional ballast from stock. I rarely surf with more than 6 in the boat (and many of them not very heavy). I’m looking for no change to surf conditions from a wave standpoint, but what I’m really seeking is something folks aren’t talking about... When I’m just driving the boat up the lake with my wife/guests in the evening, (no ballast or anything) I want to be able to cruise at 25 MPH without the doggone engine spinning that much. I came from a stern drive, and while I’m not trying to change my boat into something it is not designed to be, I would like a bit more civility in this instance...

[RDT-G23]

I would add, when reading the data posted for the 3087 prop, that the fuel burn was measured while surfing with all of the associated representations for additional ballast. (that 900 lbs of lead is the equivalent of 4-225 individuals) A prop to me is like the rear end gear ratio on a vehicle. My 3/4 ton diesel runs great with a 3.55 gear, as I don’t pull crazy heavy loads. Others, who tow bigger loads that are closer to the specified max-would lug with my gear ratio. I’d argue the same here...

[greggmck]

I know I just took an intellectual beatdown for mentioning this might happen, but given the results, I would like someone to explain again why my truck pulling the boat gets significantly less MPG at the same RPM as I do when not towing. I know the explanation made some sense, but I now have renewed doubts. (OK, it wasn't a beatdown, they were very nice about saying that it was impossible to get lower mileage with lower RPM in a boat).

I am betting that the 17.5 X 17.5 is lugging the engine, even though it works. greggmck , did you by chance open it up full throttle and see if you can still reach the rev limiter? The guys at ACME suggest you are overpropped if you can't get the RPM's all the way to the top.

Yes. The full throttle speed is listed in the results. Full throttle RPM decreased by 100 RPM and speed increased. The lower RPM could have been due the fact that it was rougher conditions when we finally tested full throttle with the 17.5 x 17.5.

[greggmck]

I would add, when reading the data posted for the 3087 prop, that the fuel burn was measured while surfing with all of the associated representations for additional ballast. (that 900 lbs of lead is the equivalent of 4-225 individuals) A prop to me is like the rear end gear ratio on a vehicle. My 3/4 ton diesel runs great with a 3.55 gear, as I don’t pull crazy heavy loads. Others, who tow bigger loads that are closer to the specified max-would lug with my gear ratio. I’d argue the same here...

Yes. That was the whole point of the exercise. To lower the RPM and improve fuel burn while surfing. We train 250 - 300 hrs / season for surfing and don't care much about anything else.