Using these formulas, Toy Boat 2 would need somewhere between 90 – 136 HP. You can sign in to vote the answer. To compound the problem, the crew from CA, who was parked next door, adopted the hillbilly and kept dragging him over for a private viewing of a stripper pole demo (that they were selling for home use). e.g. The same as airation, you are just sinking the boat lower till it gets lift from the outter hull, better stable but I don't think speed is the gain. The gas bottle would generate enough pressure to support the entire hull on what essentially would be a thin air cushion. Sounds like Terry's been in the egg nog already........LOL. His association with me made him go just slow enough to run with those guys. When you are going 40 mph it takes less hp gain to increase speed 1 mph than if your are going 90 mph. So we can say that under limited circumstances it's about 1:1. While more horsepower certainly means more speed, it will also help with handling at slower speeds or in rougher water. I believe the gear ratios are the same. The only trouble is that if the hull completely leaves the water it becomes unstable as an aircraft since it has no adequate wings for aerodynamic lift. One test I recall, perhaps in Trailer Boats magazine, tested two similar hulls and powerplants, one with MerCruiser, one with Duo-Prop. What is the max hp rating for the hull? I had the pleasure of Working at a Sewer Plant. "Give that man a Hooters Girl" See what happens when you study hard and pay attention in "guess" class.....;) Hell it had to be "Guess" class, I failed every thing else. I believe that Prof. O/B and I are both assuming that the engines being considered have the same lowers and are propped with similar props, but pitched so that each engine is at an rpm which puts that engine at the peak of it's power curve at top speed. Keep in mind that the vast majority of bass boats won’t even be able to reach this kind of speed, as only the top models are fitted with 250 hp motors. If you Fell in you would go to the bottom, no swimming. if his boat is doing 60 now with 150 HP,I'sure he'll do more with the 200!IMHO. I do feel that the Duo-Prop should yield much better control at 100+, and on your hull this alone may well prove to be a critical requirement. Depending on the hull, I thinks it more like 1mph gain for every 12-15hp. I'm not saying that it is "absolute", for there are truly few absolutes. I'd appreciate any thoughts you come up with on this idea, since it's been "gelling" for many years. That would give an ever changing curve with speed increase decreasing with straight line power increase. A more radical hull, like a tunnel or an Ally or a HydroStream will get you to 70 mph- or more. Thanks, Ed, The 'thumb suck' I was told was that doubling your horsepower increased your speed by 60% up to 100mph. Really makes you wonder how much HP it takes to push a STV at 150mph.... why would a 200 have less torque than a 150? Likewise, a hull that sits low in the water requires more horsepower to push as well, as compared to say, a hydrofoil, which rides on planes on top of the water, reducing friction. You could have two identical vehicles with the same hp but one has 3:11 gears and the other has 4:10 gears, the 3:11 gears could essentially reach a higher top speed before the rpms run out. He has been playing around with prop; height, ECT but the 6 mph gain was with his fishing setup. 317.6mph (511 km/h) was the fastest boat speed ever recorded. A setup like yours is light years beyond what I ever have tinkered with but I am sure someone here can help. I don't care about formulas.... when is someone going to confirm that I won the Hooter Girl....................................................................:confused: ...from cars and other types of vehicles, in that hydrodynamic drag limits speed more dramatically than air drag. There is another old thread here about it too, and with a more mid sized vee with one step in the back. This would depend a lot on the type of hull the motor was on. Doing the math can inexpensively predict which is best for any particular situation- and the solution is different depending on what you're running. There are many variables to be considered but on most planing v-hulls, I would think 1 to 2 mph per 10 hp would be about right. I use it myself quite often when sizing motors for large outdoor machines operating in high winds. In your case, it is a boat, so a couple of factors will affect the speed you can achieve. Happy Holidays, Ed, Ithink you meant 8.3hp per Mph increase.:D. Boats moving off the coast of seal beach at the same time 2pm. One of the difficulties is that when gas turbine cores are put to other uses they are often run at more or less conservative power levels. The federal government regulates the horsepower of outboard motors that can be installed on boats. First, get the ratio of the new higher horsepower over the old, ie, 200/150 equals 1.333 in this case. staylor please reread the original question, and my previous respondings, this has drifted away a bit. Once this number has been obtained you have to add the square root of the weight of the boat in pounds. increases speed otherwise no difference in top speed thank you. I don't agree and I think his boat (hull) more than his motor will stop him. I do believe he pitched up 1" for the 200 at 60 and I am not sure how much to hit 63. Next, go back to the ratio, 1.333, and take the cube root. Plus, when you are “light on crew,” you can expect a rather sporty toon experience… you’re not going to break any speed records, but you are certainly going to be able to speed along in the high 20mph mark and will feel rather agile doing so. Thanks, Ed . A pontoon boat with a 200 hp engine will not go as fast as a speed boat with a 200hp engine due to the coefficient of drag. Terry Taylor, I have read and re-read the original post and I don't see where Efishzion ever mentions ratios, pitch or Rpm. As such is usually a little skittish, but it has a deep leg and the drive is very low in the water. HI. If the hull is a pad-vee, the same 10lbs/hp ratio will get you about 65 mph in most cases. Obviously the "variables" you are talking about, such as drag co-efficients, I'm not so sure aren't already present in the basic parameters of the calculation. They Pumped Air in the bottom. Merc has a nice little prop slip calculator and also on this slide rule gizmo is a horsepower increase = resulting speed increase calculator. If … When using the above boat speed formula bear in mind that: The weight is the actual running weight, including anything on the boat from the crew to the engine and fuel. a 2.5 280 is (because of its power curve) still making the same tq at 6000rpm, but its still climbing to its tq peak at 7500. therefore, in the upper revs as you are going faster, there is more TQ there to counteract the extra hydro/aerodynamic resistance. Be careful with this much added power all at once, or as I recall Brits like to say, you'll be "c***-up. gain and M.P.H. We scared the hell out of them big car motors and Jon drove his ass off slowing down to run with them. I will use Briggs and Straton for my example. They put scoops on the bow and piped the air back to the pad. Use this Boat Horsepower Calculator to estimate the power required to efficiently move your skiff. This is a big hp change- from 300 to 600 hp, so many unanticipated things can happen- such as blowout or a radical increase in drag above a certain speed due to your hull form. I would expect to use this addition only for an extra amount of "dash" speed- much like nitrous oxide injection into the engine, or for extra straightaway speed for closed course racing. Horsepower is a unit of measurement of power developed by engineer James Watt in the late 18th century. In virtually all rigs I've set up, the actual result is somewhere between these 2 numbers. You need lift from the hull from the water passing by. However, this assumes that the hull drag factors for form, skin, and appendage drag remain constant. We know from experience that the hull form of a Boston Whaler moderate v-hull is typically in the range of 180 to 200 as defined above. Similar props with diffrent pitch are not the same.Again useing added hp.to turn more prop and or gear and rpm is how the hp. The only tests I've seen are at 40 knots or less, and they showed the Duo-Prop to be slightly faster. by the cube of H.P. : As Mark75H said, most of the algorithms for performance of vee hulls and tunnel hulled boats have been worked out in the book "Secrets of Tunnel Boat Design (http://www.aeromarineresearch.com/stbd2.html)", and the Performance Analysis software (http://www.aeromarineresearch.com/tbdp6.html). I have been struggling with the various answers in order to obtain a speed I wanted from my boat. Going back to the math equations that Prof.O/B and I suggested a while back provides the following results: Going from 150 hp to 200 hp with Prof. O/B's cube root equation predicts a speed gain of 10 percent, this takes you from 54 mph to 59.4 mph. I still have bad memories of testing an engine for torpedos that ran on de-ionized water and lithium to generate power from controlled gas generation. Yes I am assuming the X hp motor is ported to make maximum safe warranty-able consumer X hp at what is usually the lowest reasonable rpm it can to have more longevity. The big unspoken question though is how long is he going to be happy with whatever the speed increase is? Maybe you should lower the motors a bit or have the props cupped big. It's a bit more than is easy to relate in a single thread, but the book shows how to do all this, step by step. Simply put, it’s typically a good idea to get an outboard motor with the maximum horsepower recommended by your boat’s manufacturer, says Discover Boating. Using my more optimistic relationship of mid-way between the cube root and the square root indicates 1.33 times current speed, or 106 mph. 16' aluminum boats are popular and a 60-hp engine will typically propel them from 25 mph to 30 mph top speed, depending on load. MPH = boat speed in MPH HP = engine power in horsepower LBS = total boat weight C = constant related to the hull form. If you are talking about something like a Jonboat, with one person in it, and no other cargo than fuel, I would guess your 9.9 horsepower engine might manage about 15 miles per hour, maybe even 20 mph if you are not terribly heavy. Powered by vBulletin® Version 4.2.3 Copyright © 2021 vBulletin Solutions, Inc. All rights reserved. by anyone's standards. where. Then it takes 30 more horsepower to reach 100. Ok, had some mis-info hope this helps. A car engine can have its mile per hour-age totaled by multiplying the number of horsepower by two and then dividing by half of the number of cylinders. Heck, I made this absouletly startling guess and don't win anything. For instance, on a non-planing hull like a pontoon boat, I have seen a 50 hp increase result in only around 2mph. ;). Lets say a factory fishing motor is ported to 6/10ths of ultimate power. It is not linear. Thanks, Ed. Most boats with a 250 hp motor can reach a little over 70 mph, but anything beyond that starts getting more challenging to attain. where the drag coefficient and density of the medium don't change much during a speed change. What do you do if you drive a convertible and you park it but forget the roof down and it rains heavy outside while you are at your job? I think he should get a 200 hp engine instead of modifying his, i know a lot of people who supposedly have xxx hp after modification but never seem to hit the speed that they should and their engine life falls short. I don't think there is a formula to cover all of that. The maximum HP is determined by calculating the boat’s factor (the length multiplied by the width) and then looking up the allowable engine size in a table. The answers below will be for at sea level and standard pressure/temperature. For boats it is an entirely different story. This is with his normal fishing setup. This section could either be built into the existing pad, or slightly protrude from the existing pad. So a 600hp V6 would be capable of going 400 miles per hour. The numbers show that the triple 300 hp engines (900 hp total) have a power-to-weight ratio of 1.68 pounds per hp, while the twin 400s (800 hp total) calculate to 1.62 pounds per hp. Props, jack plates, it goes on and on, ECT, ECT. horsepower is only one factor of many in determining speed of a vehicle. How does one salvage an RV from the bottom of a lake? He right now is stuck on 60 but cant break through. Now you have the approximate top speed of what your boat will be. Install Jack Plates. The entire post is interesting reading and very informative, and I'm not trying to be an a$$, but what's your deal with the ratio, pitch, rpm scenario.
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