Prop Question
Printed From: CorrectCraftFan.com
Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=34642
Printed Date: April-27-2024 at 2:41am
Topic: Prop Question
Posted By: 69barri
Subject: Prop Question
Date Posted: September-17-2014 at 3:30pm
After poking around on these forums lately I have seen a lot of posts about hull vibration and the subsequent damage that can happen. I am currently running a four blade 14 x 20 prop on the Debonnaire and I have some vibration once I am turning over 4000 rpms. I don't run it that high very often but it is starting to worry me. I have a 1.23 to 1 transmission and a 1.125 diameter shaft. The strut is brand new to the boat. I don't know the make of the prop off the top of my head but it was a used item off eBay, so I am beginning to think that it isn't in that great of shape. Right now the hole shot it great and it tops off around 46 mph (GPS) at 4,200 rpms. Any recommendations on a different prop to try? I love the hole shot now but I wouldn't mind gaining some top speed. Engine is a 454 with about 415 hp.
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1963 Debonnaire Deluxe
1972 Separator Jet Boat
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Replies:
Posted By: Hollywood
Date Posted: September-17-2014 at 3:39pm
Used prop of unknown condition is really not much to go off.
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Posted By: 69barri
Date Posted: September-17-2014 at 4:24pm
I agree. I figured I might as well get a different prop for the boat and see if that solves the issue. Being that everything else is new, I figured it was a good starting point.
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1963 Debonnaire Deluxe
1972 Separator Jet Boat
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Posted By: Riley
Date Posted: September-17-2014 at 4:37pm
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The only way to figure out the best prop for that boat is to try different props as you've installed a high powered custom engine in it. I would think you'll have some difficulty borrowing from most Correct Craft people as you're running a 1 1/8" shaft. We're dealing with the same issue, but we've been able to borrow a couple props as we have a 1" shaft. TimB would be best at recommending props, but unless you can get a dealer to let you try different props, I don't know where you're going to find them.
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Posted By: TRBenj
Date Posted: September-17-2014 at 4:50pm
You're in luck, we just finished some testing on a big block 1.23 1-1/8 shaft boat (99 sn python) and can now make some intelligent recommendations! As expected, the stock small block 21' v-drives (1.5:1, 1-1/8") from the '00's used similar props to what you want, so there are plenty to choose from. Acme 380, 816 or 800 would be a good place to start- you can likely find a nice 380 or 816 used, the 800 3-blade never came stock afaik. All are 13.5x17.5 and pushed the 435hp python 52-54 at 4900-5150 rpm.
A nice boat like that deserves a nice prop after all you've had done to it- don't go dumpster diving on the most important part of your drivetrain!
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Posted By: 69barri
Date Posted: September-17-2014 at 4:58pm
I just found a new Acme 800 for $500 on eBay. Seems like a good deal, but I am curious about the lack of pitch in comparison to my current prop. Wouldn't a pitch reduction of 2.5" make a big difference? The speed on the SN you tested is impressive, but I doubt I will see anything like that with an older less efficient hull.
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1963 Debonnaire Deluxe
1972 Separator Jet Boat
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Posted By: TRBenj
Date Posted: September-17-2014 at 5:17pm
$500 is not a good deal at all. A used 380 or 816 can be had for well under $300. New would be around 400 if you know where to shop.
I would expect the older hull to be much more efficient than a late model SN. New boats are heavy for their size and run very bow-low in order to distribute their weight over a great surface area (making the slalom wake smaller). This large wetted surface makes them slow. Old boats are narrow and run bow high, making them much faster with equal power, generally speaking.
It is very difficult to compare prop sizes between different brand props that were finished differently (hand vs CNC). Generally speaking, acmes act a bit larger than their hand finished counterparts (the popular 13x12 540 is the stock replacement for a 13x13 federal and turns the same rpm).
Either way, i find it hard to believe that big block was built to turn 4200rpm at wot, it will most likely be happiest close to 5k. Loading it down with a big prop in an attempt to keep revs low will be much harder on an engine than letting it spin higher rpm. Spin it to win it!
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Posted By: 69barri
Date Posted: September-17-2014 at 5:20pm
Thanks for the all the knowledge, I really appreciate it. I will keep looking for a prop and hopefully will get the chance to test it out soon. I will let you know the results then. I would be extremely happy to run over 50 mph!
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1963 Debonnaire Deluxe
1972 Separator Jet Boat
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Posted By: phatsat67
Date Posted: September-17-2014 at 6:04pm
I wouldn't be such a downer about the speed. I bet that thing will impress you spinning some Rs and running a modern propeller. The hole shot on an acme will smash whatever it is you are running right now even if it weren't exactly the correct prop.
Listen to Timmy, I was there while we were playing with the Python boat.
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