Got a 2:1 gearbox in your G? I did some prop testing on an alternative....

[LakePowellMan]

I have my own fuel tank and pump at my dock. Makes it easy to keep a total of fuel used.

He usually wakeboards with just stock ballast and a few people onboard. Not sure if he has tried adding much extra ballast for wakeboarding. He does add a bunch of weight for surfing and has no issue.


lakepowellman- where do you have the 2 750s added? In the rear compartments?

For my testing, I put them on the floor on the floor in the main area in an attempt to try and mirror my crew in weight. No ballast beyond stock.

[LakePowellMan]

I really want to know the RPM results with the above referenced prop. I don't generally have a full boat while surfing, (probably not more than 5 in the boat with a surfer behind it)-so I'm not at all worried about hole-shot. (I am at 824' MSL) I like to cruise in the evenings up the river, no ballast, and not usually more than 4-6 folks in the boat. I want the RPMs DOWN in this case. I also pull kids on tubes... The 17.5 X 17.5 may be just the ticket-if the RPM reduction is significant enough to spend ~$800...

I tried the 17.5X17.5 (3087) and ACME added a .135 cup to give it more bite. RPM was nearly identical to the 3081 (18X18 .105 cup). I decided to stick with the 3081, but both are just HUGE improvements over the stock 17X17 when you have a 2:1 550 motor. It's not even close! The 3081 wins in performance (top speed/time to plane, etc) and lowers RPMs significantly across the entire range. Remember I did my testing at 5400' elevation but do the bulk of my boating at 3600', but wanted to do my prop testing at the highest elevation I would be boating. Big props goes to Jim at ACME. He worked with me on my testing and I shared my data with him and he's great to work with!

[RDT-G23]

I really want to know the RPM results with the above referenced prop. I don't generally have a full boat while surfing, (probably not more than 5 in the boat with a surfer behind it)-so I'm not at all worried about hole-shot. (I am at 824' MSL) I like to cruise in the evenings up the river, no ballast, and not usually more than 4-6 folks in the boat. I want the RPMs DOWN in this case. I also pull kids on tubes... The 17.5 X 17.5 may be just the ticket-if the RPM reduction is significant enough to spend ~$800...

I just talked to Delta. They did everything they could to steer me away from the 3047, saying it is/was too much for my engine-(H6). They really tried to steer me to the 3087 (17.5X17.5), but said that given my low generally low loads, that the 3081 (18X17.5) would be fine...

[LakePowellMan]

I just talked to Delta. They did everything they could to steer me away from the 3047, saying it is/was too much for my engine-(H6). They really tried to steer me to the 3087 (17.5X17.5), but said that given my low generally low loads, that the 3081 (18X17.5) would be fine...

Sounds to me you're getting good info from Delta...my testing data agrees. Closest I tried to the 3047 was the 2955 which was the 18X19.5 with .75 cup, and it was too much for the 550 at elevation. The added pitch just killed my performance with the 550. When I was doing my testing ACME was out of stock of the 3047, but I didn't bother testing it later because I saw what the added pitch (19.5) did to my performance, so I didn't bother. The 2955 was very near the same RPMS as the 3081. Only way to know for sure is try them out. Good luck!!

[Tallredrider]

I just talked to Delta. They did everything they could to steer me away from the 3047, saying it is/was too much for my engine-(H6). They really tried to steer me to the 3087 (17.5X17.5), but said that given my low generally low loads, that the 3081 (18X17.5) would be fine...

I wonder how that would translate to 2700-3600 feet with an H6. So I assume you bought one? Keep us informed on your impressions.

[Wayward]

First thing anyone with a 550 should do at elevation, is change the supercharger pulley...... bring the manifold pressure back up to what it is at sea level. Poof, you got sea level performance back...... the beauty of forced induction!!!

[RDT-G23]

I wonder how that would translate to 2700-3600 feet with an H6. So I assume you bought one? Keep us informed on your impressions.

I haven't bought one yet; I'm still in "due dilligence". I'll probably do it during the off-season.

[Sailfun]

First thing anyone with a 550 should do at elevation, is change the supercharger pulley...... bring the manifold pressure back up to what it is at sea level. Poof, you got sea level performance back...... the beauty of forced induction!!!

That would depend on the type of supercharger installed and it's capability to flow air. It might still be pushing the max designed airflow at 5000 feet so changing pully size would result in a change in boost even at altitude. You would also want to understand how the ECU determined fuel flow and if it has a pressure altitude input or works off A/F ratio's only. Might require a retune. Last thing to keep in mind is your warranty is done if you change the pully.

[Wayward]

That would depend on the type of supercharger installed and it's capability to flow air. It might still be pushing the max designed airflow at 5000 feet so changing pully size would result in a change in boost even at altitude. You would also want to understand how the ECU determined fuel flow and if it has a pressure altitude input or works off A/F ratio's only. Might require a retune. Last thing to keep in mind is your warranty is done if you change the pully.

Ya...... it was more of a joke. (mostly for the warranty end of it)

The LSA doesn't have any ability to bleed off excess boost, so they don't oversize it. It is sized, and run at a speed to move a certain amount of air at sea level. Less atmospheric pressure does have an impact on it. Less in, less out, but the difference is less than if it was naturally aspirated. Turbocharged engines, on the other hand, have more ability to make up for altitude changes. Turbos usually have the ability to move more air than is required, and then use a wastegate to bleed off the excess. They have a certain amount of makeup ability at higher altitudes.

In boats, the ECU uses a speed/density calculation to determine fuel flow. Speed density calculations are based on inputs from a barometric pressure sensor, manifold absolute pressure sensor, intake air temperature, and throttle position. PCM doesn't use a mass air flow system or a mass air flow sensor. No engines use A/F ratio data from O2 sensors to determine base fueling. They are only monitored for very small fuel adjustments during light throttle cruising conditions. O2 sensors are ignored under any sort of load condition, or throttle positions above 10% or so.....

So, basically, yes, the ECU would be able to compensate for a proper pulley sizing at altitude. Bring the boat back down to sea level, and you might have a problem with the ECU seeing an air flow out of its normal range.

[HyperliteCowboy]

I tried the 17.5X17.5 (3087) and ACME added a .135 cup to give it more bite. RPM was nearly identical to the 3081 (18X18 .105 cup). I decided to stick with the 3081, but both are just HUGE improvements over the stock 17X17 when you have a 2:1 550 motor. It's not even close! The 3081 wins in performance (top speed/time to plane, etc) and lowers RPMs significantly across the entire range. Remember I did my testing at 5400' elevation but do the bulk of my boating at 3600', but wanted to do my prop testing at the highest elevation I would be boating. Big props goes to Jim at ACME. He worked with me on my testing and I shared my data with him and he's great to work with!

LakePowellMan...I agree. I have not done as extensive testing as a lot of other people here, but based on my research, info I got from Delta and ACME, and then ultimately buying and using the 3081....its hands down one of, if not, the best prop for a 2:1 550hp. I know there are obvious differences between that and the guys with the 450hp, but based on my conversations with the experts and my own research and understanding, if ACME and Delta tell you to use a certain prop, I would listen all day long.

Its ridiculous how much more "calm" my engine is....all while pulling just as hard more efficiently and more quietly.

[ffmedic74]

Would be great if nautique finally came out with a "high/low" gearbox. One gear for surfing and the other for cruising.

Sent from my SM-G900V using Tapatalk

[Sailfun]

It's been done before. I think it was Sanger who had a two speed trans.

[thtrog]

It's been done before. I think it was Sanger who had a two speed trans.

MB

[Tallredrider]

It's been done before. I think it was Sanger who had a two speed trans.

I think it broke too often to be practical in a wakeboat. These boats break down too much as it is. maybe a new and improved version would be the ticket.

[Sailfun]

Or a variable pitch prop like aircraft and some larger boats use.