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Masher

To change or not change my prop - that is the question.

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Masher

I have a 2013 VTX. Typically surf with stock MLS full, 550's in the lockers, 700 front bow sac typically half filled or so, surf gate deployed and a couple clicks up on the wedge. I am finding with more than 3-4 people in the boat I am having a hard time getting speeds above 10 - 10.5 mph and have to start cutting back on ballast. Thinking about changing prop but have some questions.

I am thinking about changing from the 573 to probably the 1273. ACME also suggested considering the 1847. I am confident this will improve surfing but wondering if a change in prop will have any effect on the wake characteristics at slalom ski speeds, or is it the hull shape alone that defines the wake? I like to slalom and don't want to negatively affect the wake.

I see others post they get around 46 mph at wide open throttle. I did a WOT test and get 40 mph at 5015 RPM.

I have a FAE installed and am wondering how much extra drag there might be possibly causing decreased top end speed as well as when the boat is loaded down and trying to plane ??

One last point. I also want to barefoot on a boom. I anticipate the 1273 will retain sufficient speed to barefoot. Any issues with RPM at 38 to 40 mph with that prop? What RPM range should be maintained (both for surfing and slalom / barefoot) to keep the engine happy ?

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nutoz

Let's see , you want to ski with no wakes ,you want to surf and wakeboard with weights , you want to go fast for bare footing. You want what every one want. A variable pitch prop and 2 speed transmission to cover all.. You will have to pick a prop that suits 75% of your activity like rest of us . good luck. I am diciding on different prop my self and having hard time. Good luck to you

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SkiZilla

Out of curiosity are you sure the boat currently has a 573 on it. Most of the boats brought into our area are equipped with the 1235 ("Altitude" prop). Ours has the 1235 on it and the speed / rpm numbers at WOT are almost identical to what you have posted at what I am assuming is similar elevation. (Where are you usually using the boat?)

To answer your questions we find the 1235 to be a good choice we ski 75% of the time and surf the rest (listed with aprox 2200 lbs plus crew) and the prop has never failed to get on plane or give up.

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obski

He probably meant the 537 prop. My fnigres gte ahaed of me soemtiems too.

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Ndawg12

Subtract 2 mph at the most for drag from the FAE, so you should be getting ~42, that's still too low for a 537 unless you're at high altitude...? Also what motor?

Edited by Ndawg12

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Masher

Sorry I did mean to say 537. When I bought the boat this year the dealer told me that was the factory prop that came on it. I have the 350 Monsoon and operate at about 2700 feet above sea level.

We mainly surf and ski between 30-34 mph. Since I put a barefoot boom on to teach kids and newbies, I was hoping to do some bare footing on the boom also, but that would be occasional at best.

I read a different thread warning about stressing the engine by operating at too low of RPM's when the boat is heavily loaded, and recommending selecting the correct prop to stay in the engine's happy zone. Just want to make sure I am not red lining it on the other end, depending on what choice I make. I could live with not pushing it much past 34 mph if required.

Most seem to say the 1273 is is like the 1235 with more cup and retained top end speed. That's what I was thinking about changing to.

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shawndoggy

I'd go 1235. You'll still likely get to 41 or so before bouncing off the rev limiter. Your altitude is limiting your top end... if you can only hit 5000 rpms, you are under propped. 1235 will get you to redline at WOT and will have no loss of performance in the intermediate ranges (might turn slightly higher rpms, but your boat should pull much better with more weight for surfing, etc).

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mattpoland

1235 for your set up. The extra diameter of the 1235 vs the 537 will get you much better surf performance and also be more efficient in the 30-34 mph range. Your rpms will probably be only 100-150 rpm higher for skiing. What you'll lose is a couple mph on the top end. My last boat went 42.5 with a 537 and 40 with a 1235. You'll be just about redline to barefoot, or maybe you can get some of those shoe skis so you can go a little slower. I purchased, and then returned a 1273 because it cavitated at wakesurf speeds for me.

Edited by mattpoland

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williemon

Most DD ski specific boats seem to maintain a 1 to 1. 3200 rpm for 32, 3400 for 34 mph and so on. I've heard over the years that 2500 to 3500 rpm is often the more sought after cruise and efficient rpm ranges for most 4 stroke gasoline marine engines so I select for that provided I'm not lugging at wide open throttle. If anything, I will prop where it might over rev.

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chrisnorem

I run a 1273 on my 14 vtx with a 350 and it is great. As close as you are going to get to what you want.

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Sixer

My VTX came with a 1939. Would the 1235 significantly change things in my boat???

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