G23 H6 Prop Change for improved GPH efficiency and noise

[mattyjman]

Hey y'all - I've read a few seemingly conflicting threads regarding adjusted props and looking to see if there is any consensus. The prop on the boat I'm getting needs to be replaced so I'm wondering if I can preemptively make a change that will improve GPH and noise to suit our needs. The boat is 2017 G23 with H6 motor. We're probably going to skew more 50/50 surfing/cruising and floating for the first year of ownership, nothing over stock ballast and typically a small crew. Is there a prop that I should look at that will increase top speed, reduce noise, and increase fuel efficiency knowing we aren't lugging around huge crew and super weighted down G?

I heard the 3087 tossed around a bit, and on ACME site they have 3043 as an option. Any thoughts?

[shag]

Although not familiar with those prop m models, generally - if you are looking for more top end - your surfing/out of the hole performance may suffer. Maybe someone with more experience can chime in ... These are heavy boats to start with, and I would think a prop that gives more top end (for cruising at a lower rpm) - may tend to be a lower performer low end wise. Maybe I am wrong,

[greggmck]

In 2018 I did extensive testing on several propellers, sharing the results with ACME for their sales team to help customers looking to improve surfing performance. That said, I did NO testing for wakeboarding.

Here is what I posted:

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 tests

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 was very satisfied with the sound reduction of the 3087 but the increase in fuel burn is a problem for me (we put 275 - 300 hours a season on our boats).
I would NOT suggest going to an even steeper pitch/larger prop with the H6DI as I would not want to put any more load on the engine.

The 3087 did reduce noise (by rotating at lower RPM) but fuel burn increased noticeably. And in practice any prop that does reduce noise, must reduce RPM, but also increase fuel burn since the engine will run less efficiently to generate the same power to push the boat at a slower RPM. The stock ACME 2561 is a very good choice for balancing noise and fuel consumption. Perhaps that is why Nautique engineers chose it .

So if I wanted to reduce noise and were willing to compromise some fuel consumption, I would seriously consider the ACME 3085. It has the same 17.5" diameter as the 3087 but with a 17" pitch and less propeller cup. These changes should reduce noise somewhat over the stock 2651 while burning less fuel than the 3087.

[mattyjman]

In 2018 I did extensive testing on several propellers, sharing the results with ACME for their sales team to help customers looking to improve surfing performance.

Yeah I saw that thread. I'm confused though, on how you ended up with an INCREASE in fuel consumption while another thread I reviewed testing with the supercharged engine led to a DECREASE in fuel consumption. Do you think there was anything about your situation, like all the extra weight you run, that somehow led to that result vs a lower consumption? Not knowing a whole lot in this arena, it just has me scratching my head a bit.

[greggmck]

The boat weight was fixed in all cases, moving the boat forward at the same speed with the 3087 prop, tuning at lower RPM, causes the engine management computer to increase the fuel air mixture ratio and advance ignition timing to produce the same power as the 2651 turning at higher RPM (with a leaner mixture). F=MA. In both cases, the boat cannot move forward at the same speed without doing the same amount of work. However, modern engines are designed to run as efficiently as possible. Less load on an engine results in a leaner air/fuel mixture and greater fuel efficiency. All things being equal, loading the engine with a larger diameter and greater pitch prop will decrease engine efficiency because the engine management system will dump more fuel into the engine to produce the equivalent power to achieve the same speed.

If someone mentions propeller slip as the reason this is untrue, please do your homework... Slip INCREASES as load increases on any given propeller/engine combination.

I cannot speak to the supercharged engine statement. I did not do the measurements.