Prop question/suggestion/problem |
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Tom, I'm always "fuzzy" so I too was wondering what boat we're talking about. I went back and did find it .
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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Because I have whined about it so much the boat was so far back haha.
Its a 1994 American skier Tbx 350 merc 1:1 Wonder If I should call up eric at oj and see what he says. |
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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I'm not sure more opinions are going to help, you seem indecisive enough!
![]() I doubt Eric is going to tell you not to trade your Acme for an OJ. Is this OJ local? Try before you trade? I agree with Tim finally, I'm inclined to go for the 11" pitch over your 12". |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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Ok I'll jump in with the "fuzzy" guys here.
What I'm fuzzy about is why you don't figure out what the boat had for performance when it was new and down in the flatlands then you can figure out what it realistically is capable of at altitude How are you gonna do that you ask? Pick up the phone and call the guy who has been more than a little familiar with American Skiers over the years. At different times he has worked there designing the boats or later on owned the company. You go to his website so you should be familiar with him since he's on it frequently. I'm sure he could tell you what it would do speed wise at sea level, what it has for an engine, what it's power was, whether that hull has lots of drag etc You're up 5000 ft so your power is down by about 15% to start with no matter what. Here's his number 985-542-4336, just ask for Ron You'll get a lot of good info on the phone actually talking to him. Good luck KenO |
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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not according to someone on here who i won't name but it starts with T and ends with j. |
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Per the Wallace Racing engine HP/altitude calculator, it looks like 10% is a closer figure at 5000' |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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I have talked to ron multiple times and he is an awesome person and is super knowledgeable about all DD boats in general. But he was the american skier lead engineer I believe up until 1990 then he owned the company from 96-01ish then it was bought and called Elan. The problem is my boat is a 94 and from 91-95 AMskier was owned by a company called WESMAR. The problem with that is there is no records at all of any of their boats, testing info or anything. Alot of the boats used different parts from another boat of the same model. So I could prop get info on the 96 and up tbx but by then they had made hull changes.
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Engine has how many hours on it?
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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Pete
Your math ain't too good. I went to your Wallace Racing Guide Plugged in 5280 ft and 260 hp at sea level and it spit out 41.1 as the power loss. How many percent is that? I'm a little fuzzy KenO |
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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@ 5000' it's spitting out 15% exactly
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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94 Waterski Mag buyers guide. Page 39 has a TBX with a Ford engine for some reference info. For the CC guys you have 4 or so boats tested in the same issue for some good reading. Hope the link works |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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Pete's abacus obviously had a malfunction |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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900hours
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Can you demo that 11" OJ?
Woof, TBX is a big girl. 2650lb |
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Orlando76 ![]() Grand Poobah ![]() ![]() Joined: May-21-2013 Location: Mount Dora, FL Status: Offline Points: 3108 |
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I think it'd be easier to move to sea level.
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Please support The Cystic Fibrosis Foundation
1976 Ski Nautique 351 Escort 1993 Ski Nautique purple and black 351 HO PCM |
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63 Skier ![]() Grand Poobah ![]() ![]() Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4256 |
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So the rock solid ski boat advice we're giving you is to move to the coast and lose 30 lbs. Problem solved! In my simple mind after reading a lot of stuff about speed vs. HP, I've come to believe that in small boats in the 17-23 ft. range it generally takes 11-13 HP to gain 1 mph. Inboard ski boats, with the shaft angle and design purpose of planting the bow, may take a bit more, 13-15 HP to gain 1 mph. If we take the 15% power drop that is mentioned above as being 260 HP x 15% = 39 HP, then we're I think pretty much agreeing your engine is putting out more like 220 HP, and at 900 hours maybe it's even 210 HP. My point is that I'd expect about a 3 mph drop from running that same boat at sea level. |
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'63 American Skier - '98 Sport Nautique
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TRBenj ![]() Grand Poobah ![]() ![]() Joined: June-29-2005 Location: NWCT Status: Offline Points: 21141 |
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Power is down due to the reduced oxygen in the air at higher altitude. This reduced power level moves the entire hp curve down. It does not change the fact that the engine will produce max power at 4600-4800. (Ie, using the 15% reduction quoted above, he's effectively working with 220hp @ 4600-4800.) Lower power output is evidenced by the fact that he can only pull the 541 4200rpm or so. He needs less pitch to get the rpm back up to 4600-4800 in order to maximize performance at his altitude. Ultimate power (and speed) will obviously be lower at 5000' vs sea level. We are trying to maximize performance within the constraints he has. Sorry, thought this was painfully clear from the outset. Maybe someone needed to explain the basics. |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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Thanks for that I did not know the specific numbers. I think ill try the new oj prop and then just be happy and save up for a gt40 176 if I can find one in a few years.
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skutsch ![]() Grand Poobah ![]() ![]() Joined: June-19-2008 Location: Racine, WI Status: Offline Points: 2874 |
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So basically we just need to come up with a "Ready to install" Marine Supercharger!!! |
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tryathlete ![]() Platinum Member ![]() ![]() Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1797 |
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It's not really debatable. It's physics. Your BHP loss computed from your BHP of 260 at sea level and Elevation of 5280 feet is 41.18 HP loss. |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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I just need to add alot of stickers. At 5hp a sticker I should have lots of power soon.
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Make sure that thing is tuned up right. That OJ prop has less blade area, another helper in getting more RPM. The American Skier Advance hull doesn't seem to react significantly to aft weight for speed gain, but do play around with this some. Run minimal weight inside the boat especially up front (passengers). Running a full tank of gas may actually help as you said the rearward weight did pick up some speed. That hull does plow quite well, you may *want* to maintain some aft weight.
Get an extended pylon and shorten up your rope to 70'. Your engine will be happiest running higher RPM but you may find that the pitch sacrifice (& other prop design features) will not produce highest top speed. The ACME rake is also going to help get the nose up, more speed to be gained. We really need to find out how many RPMs you can really pull, then narrow down the prop selection. Really. |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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Yeah I have a tower on the boat it came with it. Its off right now but I will put it back on. We ski off the boom alot. And your saying 70' is better than 100 or 90. That makes sense more rope angle.
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Hollywood ![]() Moderator Group ![]() ![]() Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Shorter rope = less rope = less weight. You are holding the rope, you're supporting its weight.
Shorter rope = more upwards angle = less weight supported by your feet (skier + rope) Consider ditching the tower.
SharkSN stripped down a green TSC "superwake" and replaced a bunch of [necessary] components with carbon fiber. Fluid Motion Sports |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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I can get my hands on a high fly buddy has one he never uses. I dont really care much about longline right now I ski boom 80% of the time.
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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I have found a OJ 304 13x11 .9cup forsale used and im going to buy it hopefully today. I hope it works out well. If the CNC OJs are close to the acmes It should be right inbetween the 913 and the 1609
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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Hi LC
Thinking some about your prop dilemma and being one of them guys that has props that go both ways, I went and looked thru my collection of what some people would call worthless boat anchors to see what I had. I have an old Michigan 13x12 Lefty that I could send you to try, You can see what it does for your RPM's/speed. Your present boat anchor is doing pretty good, ( you liked the anchor better than the 541) so this would be like an anchor to anchor comparison with 1'less pitch. It's got no dings, I'm not sure where I got it or if I ever used it on anything. ![]() Let me know if you're interested, With my best Billy Mays impression I'll say no charge, so it's gotta be worth a try. KenO |
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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Keno, I really appreciate the offer. I just bought a prop today Its a XMP OJ 13x11. And I also looked the other day and my buddies spare prop is a old13x12 so I threw that on my boat last night just to try. It would probably give about the same results as yours. I really appreciate the offer tho.
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10810 |
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so how'd the 13x12 do just out of curiosity?
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lcgordon ![]() Gold Member ![]() Joined: June-24-2014 Location: Denver Status: Offline Points: 500 |
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Im going to test this weekend. I just put it on last night.
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