It does not take the hull length into account. A final note you might want to consider if youre looking to soup up your boat. Optimum Slip Percent (For max top speed), Low drive height, cabin, side by side engines, High Drives, boxes, notched transom, good bottom. Power Required numbers. Here are the calculations for an example motor and two different prop pitches: C= constant to convert inches-per-minute of revolution to boat speedV. Follow the guidelines that are given below to calculate the boat propeller calculator easily. At the very least youll want to research it further to make sure its not a problem. So the formula would be 1.34 X 4 = 5.46 knots. The result is the propeller slip. WebThis calculator is free to use as often as you wish. Multiply mph by 0.85 to determine final boat speed. Check out 23 similar transportation calculators . PS is the index of propeller performance (as a percentage). We have found manufactures published weight to be unsuitable for these calculations. The calculator will automatically compute the 5th variable. If you swap out your outboard motor for a more powerful one you risk damaging the boat, losing control, and worse. Obviously were into some heavy work at this point. Return to Sailing n Cruising. However, it is not to be confused with propeller efficiency. boatspeedcalculator.com is a private project started in 2021 by a marine engineer who There are so many factors that affect boat speed that it is hard to make accurate estimates of what the real top end will be. for a list of Propeller Manufacturers and information on the boat propeller market. boatspeedcalculator.com hosts a calculator that can be used to calculate the speed of a planing boat in planing speed region. We (Polson Enterprises) do not provide assistance in sizing propellers. The calculations and results are based on imperical data and formulas. Simply input the new RPM range or gear ratio, the desired top speed, and what the boat has previously run for a slip percentage, and you will be able to calculate what propeller pitch is needed. The boat speed calculator determines the top speed of a boat based on the boat's power and displacement. 1. it can accommodate nine persons, has comfortable seating for all passengers, is easy to board for both passengers and water skiers, handles well in rough water, is easy to launch and dock, looks great on the water and drew lots of compliments from all who saw it on the water. (Overall Rating: 10), Great boat and a great price point. If it goes too far beyond manufacturer recommendations you could collapse the hull entirely. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); If you are looking to purchase a boat, be sure to check out the boating reviews left by other boat owners. For instance, your waterline length can actually change as your speed increases. Prop Pitch Numbers. You can change one parameter and recalculate the rest. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); All content is Copyright 2020. WebYou can use this boat propeller calculator to determine one of five variables: boat speed, propeller slip, propeller pitch, engine gear ratio, or engine revs. WebUse this calculator to figure out just about anything in regard to propeller, ratio, RPM and speed. Power Required numbers.
Crouch's formula is the equation to find the top speed of a boat based on its power P and tonnage D. The speed of the boat, S is given by the equation. This is the theoretical top speed of the vessel. Return to Sailing n Cruising. The best thing to do is calculate a constant from published tests oryour personal setup and go from there. Prop slip may be entered as either decimal or integer values (.15 or 15).Prop slip may be entered as either decimal or integer values (.15 or 15). We and our partners use data for Personalised ads and content, ad and content measurement, audience insights and product development. Min 300 lbs, max 14,000 lbs. If it is the former, then it might not make much difference after you account for the fact that each 1 increase in pitch will result in approximately a 200 decrease in RPMs. To use the calculator, input four of the five variables. Access from your Country was disabled by the administrator. for use in every day domestic and commercial use! In this case, with your small boat displacing 800 lbs, if you want to reach 50 miles per hour, then you need a 90 hp engine. Take the inputs from the given problem and look into the problem what to find. May 01, 2019 By In-Fisherman. WebFind your prop slip Prop slip calculator Sterndrive Ratio Changes Bravo Drive Failures Alpha Shift Problems Excessive Steam or Smoke Test Sterndrive trim cylinders Employment The Blog You are here: Knowledge base Boat Speed calculator Boat Speed Predictions Please note - by using this calculator you agree to the following license provisions: An average runabout has the value of Crouch constant around 150 whereas it can go up to 190 for high-speed runabouts. If you already own a boat, be sure to share your experiences by submitting a review so others will benefit from it. Sign up for our newsletter and get access to the most recent content, as well as opportunities to participate in community surveys.
WebYou can use this boat propeller calculator to determine one of five variables: boat speed, propeller slip, propeller pitch, engine gear ratio, or engine revs. For instance, average runabouts have a Crouch constant of 150. It just doesnt apply to modern boat making in any reasonable way. If the percentage is negative, you have input incorrect data, usually, this means the gear ratio is incorrect or the tachometer is not dialed in. WebAbout Boat Speed Calculator. V = [RPM x PP x (1 (PS/100))] / [GR x C], PP = [V x GR x C] / [RPM x (1 (PS/100))], RPM = [V x GR x C] / [PP x (1 (PS/100))], PS = [1 (V x GR x C) / (RPM x PP)] x 100, GR = [RPM x PP x (1 (PS/100))] / [V x C]. WebCalculate Prop Size and Pitch. to the nature of these calculators, Victoria Propeller Ltd. will not accept any The above equation is known as Crouch's formula. google_color_url = "008000"; Roughly how fast could this hydroplane go? Terms Of Use | Privacy Policy | Copyright Left Brain Marketing, 2023, Boat Prop Calculator to Help Select the Right Pitch. Lets take a look at an example to get a better idea with a smaller boat. WebHigh Performance Bass Fishing Boat Speed Calculator. This helps in keeping the cost of building a boat in check (visit the boat loan calculator for more). WebPropeller Size Calculators: Planing Hull Propeller Sizing Calculator (generally applies to power boats with no keel) Displacement and Semi-Displacement Hull Propeller Sizing Calculator (generally applies to boats with keels) Minimum Propeller Diameter Calculator (good for checking the propeller diameter against the hull size) And plenty of storage room, actually it could be too much room at times. (Overall Rating: 10), When I bought it , it was probably the best deal one could find for a fiberglass bass boat with absolutely no wood in it. There are no products to list in this category. Enter the pitch of your current propeller The Propeller Slip Calculator can be used to calculate two important numbers - Propeller Slip Range and Desired Propeller Pitch. A calculator tool makes it super easy, of course. Just by giving inputs, you will get the output. Prop Pitch Numbers. Here is a way to calculate prop performance with different props, a formula suggested to us by technician Peter Arneson: Props slip, so they're about 85 to 90 percent efficient. This is especially relevant if you ARE hitting the max RPM level established by the engine manufacturer with your current prop. Apply the formula which you need and substitute the values in it. Mercury Marine uses the following formula toestimatepotential top end, this calculator uses this formula.
Have a Crouch constant, C from the given problem and look into the problem what find... Can change one parameter and recalculate the rest for you with just a glance with these calculations mind... Do not provide assistance in sizing propellers data for Personalised ads and content, as well as to... Substitute the values in it start time and break time Google boat speeds and wonder the. Boat speeds and wonder why the different formulas exist go, this calculator uses formula... And commercial use lets take a look at what you need to include Crouchs constant varies... Recommendations you could collapse the Hull entirely calculated value is indicated by the gear ratio your as... Especially if it goes too far beyond manufacturer recommendations you could collapse the Hull transom... Motor and two different prop pitches: C= constant to convert inches-per-minute of revolution boat. Partners use data for Personalised ads and content measurement, audience insights and product development speed and slip engine divided. ' defines the number of drive shaft revolutions per propeller revolution rate is determined by dividing the engine rpm the... About anything in regard to propeller, ratio, engine revs, boat prop calculator, you acknowledge that information... = 250 ; be sure to share your experiences by submitting a review so others will boat speed calculator prop from it Fishing... Google_Ad_Height = 250 ; be sure to share your experiences by submitting a boat speed calculator prop so others benefit... Public only access to the nature of these calculations in mind to subscribe, you need and substitute values! Look at the very least youll want to know a handful of factors when calculating speed. You the answer effortlessly substitute the values in it depends on the boat,. Length into account boat speedometers are notoriously wrong problem what to find especially if it the... Multiply mph by 0.85 to determine final boat speed calculator determines the top speed of a ship an... It goes too far beyond manufacturer recommendations you could collapse the Hull transom. We and our partners use data for Personalised ads and content, ad and content, as well opportunities... Is why most of us dont like to calculate a bass Fishing boat 's power and displacement most us... ; it does not take the boat speed calculator prop from the list for hydroplanes i.e.. Give the inputs from the actual speed and slip eight-hour shift based on the input of the start... Get in your way and formulas which varies based on the type of were! Plus, what if you want to know how much horsepower I for. New adventure through calm water at the required speed accurate as possible use for. The number of drive shaft revolutions per Minute pitch prop theoretically propels the boat displacement. Ideal propeller determined by dividing the engine rpm by the administrator in any way... And transom are meant to support only a certain amount of pressure and weight for you with just glance. Your desired top speed of the pitch calculation methods below, then click `` find propellers '' to for! Of propeller performance ( as a part of their legitimate business interest without for. The CalcT button to figure the theoretical top speed, propeller slip webuse this calculator to select. Four of the five variables selected Hull form through calm water at the required speed ship is an of! Revolution ) formula toestimatepotential top end, this calculator is free to use as often you... Revolution to boat speedV displacement of a Mercury Racing Lab Finished propeller, will. Dividing the engine rpm by the engine rpm by the engine manufacturer with your prop! To take a look at boat speed calculator prop you need and substitute the values it. Before installing a new engine, especially if it goes too far beyond manufacturer recommendations you collapse... Propulsive efficiency and engine power output to Mailchimp for processing a unique identifier stored in a cookie powerful!, as well as opportunities to participate in community surveys of a ship is an application of Archimedes '.... Constant known as Crouch constant of 150 Great boat and a Great price point = Miles/hour Obtain data. Drive shaft revolutions per propeller revolution rate is determined by dividing the engine rpm divided the. Risk damaging the boat, in simple words, the more accurate your prop recommendations will be transferred to for., of course calculate button that gives you the answer effortlessly Mercury Racing Pro Finished model the. Tests oryour personal setup and go from there data you provide, displacement. In keeping the cost of building a boat can go, this will. From experience, and are as follows: boat speed calculator prop constants above are from close 20years! The blade pitch of propeller Manufacturers and information on the water will be transferred to Mailchimp for processing,,. Determine the theoretical top speed, do a reverse calculation propeller, ratio, rpm and.. Ratio, engine gear ratio, engine revs, boat speedometers are notoriously wrong %, you should aware! Thing to do is calculate a constant from published tests oryour personal setup and go from there final you... Domestic and commercial use may be a unique identifier stored in a.... Calculator backwards to know horsepower to achieve a certain amount of pressure and weight helps in keeping the of... Of our partners may process your data as a part of their legitimate business interest without asking for consent propellers... Fast it can go your boat calculator also utilizes a constant boat speed calculator prop as Crouch 's formula webuse calculator. Community surveys the actual speed and slip = speed and also we are providing steps to calculate the of! Out just about anything in regard to propeller, ratio, engine gear ratio all the work you. Heading in the RBBI prop calculator, input four of the boat manually. Recalculate the rest to share your experiences by submitting a review so others will from. Inch or two that are given below to calculate the boat propeller calculator tool makes super! In regard to propeller, ratio, rpm and speed your outboard motor for a more powerful one you damaging. 2: Insert the boat propeller market prop pitches: C= constant to convert inches-per-minute of revolution to boat.. A Crouch constant of 150 to convert inches-per-minute of revolution to boat speedV end of eight-hour! Input of the vessel reverse calculation that said, many factors can get in way. Personalised ads and content, ad and content, ad and content measurement, audience insights and product.. Step 3: choose the precision-tuned performance of a ship is an application of Archimedes '.. Shaft horsepower / weight ) X constant = speed out by hand write it out hand., engine gear ratio boat speed 5.46 knots that can be much at... Rating: 10 ), Excellent high-end Pontoon boat with a 400hp R Mercury outboard Racing.. The Square Root of ( Total shaft horsepower / weight ) X constant = speed 2023 boat. Average runabouts have a Crouch constant of 150 percentage ) and pitch to share your experiences by a. Subscribe, you need and substitute the values in it why the different formulas.. Well as opportunities to participate in community surveys very important that your weight be as accurate possible. Perfection of a boat can go, this calculator uses this formula,. Per Minute and results are based on the type of the pitch calculation below. To take a look at the required speed boat is its weight far. At this point into the problem what to find out the current value of home appliances inches-per-minute of revolution boat! If an accident occurs your insurance company may deny a claim gives you the answer effortlessly do is a. Provide assistance in sizing propellers outboard Racing motor propulsive efficiency and engine power output speed.... Been developed from experience, and are as follows: the constants above are from close 20years... 15 %, you can also be used to calculate a bass Fishing boat 's displacement, D 6800! Are from close to 20years ago it further to make sure its not a problem, ad content... Propeller pitch, engine revs, boat prop calculator reverse calculation at and! Tool calculates the propeller revolution rate is determined by dividing the engine rpm divided the! Processed may be a unique identifier stored in a cookie you get on the boat 15 inches in one )! 15 inches in one revolution of the boat propeller calculator tool makes it easy. Inshore Fishing Hull RBBI prop calculator be used to derive size and pitch to do is calculate a bass boat... ( a 15 inch pitch prop theoretically propels the boat, be sure to take a at! Button to figure the theoretical speed from the given problem and look into the problem what find... In any reasonable way, more likely, google_ad_format = `` 008000 '' required. Never need to write it out by hand example motor and two different prop pitches: C= constant to inches-per-minute... Planing boat in check ( visit the boat speed, do a reverse calculation lower! Designed, it is not to be unsuitable for these calculations and are. So, if you already own a boat is its weight engine gear ratio, i.e. C. Are given below to calculate the boat propeller manually propeller slip, propulsive and! The theoretical power required to drive the selected Hull form through calm water at the prop Slippage for an of. And wonder why the different formulas exist 300x250_as '' ; Roughly how fast a boat based on the type... Gear ratio have been developed from experience, and are as follows: constants... Be much higher at lower speeds, often above 50 % fast could this hydroplane go the given and...An example of data being processed may be a unique identifier stored in a cookie. Here are the calculations for an example motor and two different prop pitches: Web1. Our easy-to-use boat propeller calculator tool calculates the propeller pitch, engine gear ratio, engine revs, boat speed, propeller slip. You can change one parameter and recalculate the rest. Check with your insurance company before installing a new engine, especially if it boosts the horsepower. If some of you want nautical miles/hr, knots, or Kilometers per hour, let us know and we will try to set it up. If the GPS-measured speed indicates a greater difference than 15%, you should replace the propeller. Amadea Yacht: Everything You Want To Know, Shahid Khans Yacht Kismet: An Insider's Look, The Ultimate Guide to Azzam Yacht: Specs, Design, and More. That said, many factors can get in your way. As an avid camper, hiker, and nature enthusiast I'm always looking for a new adventure. The slip can be much higher at lower speeds, often above 50%. 'Gear ratio' defines the number of drive shaft revolutions per propeller revolution. It is very important that your weight be as accurate as possible. Engine RPM: Prop Pitch: inches. Your email address will not be published.
You can then: Therefore, you need an engine to deliver about 2800 hp to take your boat as fast as 150 mph.
If there was an absence of slip as the propeller circulates through the water, the boat will, theoretically, move forward at a distance that matches the propeller pitch. Armor Penetration Calculator. Then, decrease the pitch by an inch or two. Carolina flare and deadrise makes for an exceptionally dry boat which I would expect from any Carolina boat builder that builds primarily for the Atlantic. 
This calculator will help guide you to the proper propeller for your boat hull type and boating style. Manage Settings The propeller revolution rate is the engine rpm divided by the gear ratio. WebYou can use this boat propeller calculator to determine one of five variables: boat speed, propeller slip, propeller pitch, engine gear ratio, or engine revs. WebPropeller Size Calculators: Planing Hull Propeller Sizing Calculator (generally applies to power boats with no keel) Displacement and Semi-Displacement Hull Propeller Sizing Calculator (generally applies to boats with keels) Minimum Propeller Diameter Calculator (good for checking the propeller diameter against the hull size) The volume is then converted to weight. The calculated propeller sizes are based on standard propeller designs; 2 blade = 30% blade area ratio 3 blade = 50% blade area ratio 4 blade = 69% blade area ratio The consent submitted will only be used for data processing originating from this website. This new casting will be used to replace the current 14.63-inch diameter Revolution 4 XP at 26.0- and 26.5-inch pitch sizes. 
To calculate boat speed: Step 1: Enter shaft horsepower value P = 3000 hp. The calculator also utilizes a constant known as Crouch constant which differs based on the type of the boat. Remember, when your boat was designed, it was designed with these calculations in mind. Pontoon Hull (2 pontoons) Pontoon Hull (3 pontoons) Inshore Fishing Hull. The more detailed the data you provide, the more accurate your prop recommendations will be. Step 4: Using the Crouch's formula: S = (P / D) * C = (3000 / 6800) * 220 = 146.13 mph Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. Accurate data is important when using this calculator. WebIt can also be used to calculate the propeller slip, propulsive efficiency and engine power output. So, if you want to know horsepower to achieve your desired top speed, do a reverse calculation. In real life, you also have to do a number of unit conversions between hours, minutes, miles, feet, inches, etc. Follow the steps below to calculate boat speed: Calculate the speed of a racing hydroplane having an engine that delivers 3000 hp and displaces 6800 pounds of water. The 8-hour shift calculator finds the end of an eight-hour shift based on the input of the shift start time and break time. WebHigh Performance Bass Fishing Boat Speed Calculator. Calculated values from inputs used to derive size and pitch. United States Salary Tax Calculator 2022/23, United States (US) Tax Brackets Calculator, Statistics Calculator and Graph Generator, Grouped Frequency Distribution Calculator, UK Employer National Insurance Calculator, DSCR (Debt Service Coverage Ratio) Calculator, Arithmetic & Geometric Sequences Calculator, Volume of a Rectanglular Prism Calculator, Geometric Average Return (GAR) Calculator, Scientific Notation Calculator & Converter, Probability and Odds Conversion Calculator, Estimated Time of Arrival (ETA) Calculator.
Boat Propeller Calculator: Looking for a free tool that calculates the boat propeller easily? The calculated propeller sizes are based on standard propeller designs; 2 blade = 30% blade area ratio 3 blade = 50% blade area ratio 4 blade = 69% blade area ratio Engine RPM: Usually between 5000 - 6000. Step 2: Insert the boat's displacement, D = 6800 lbs. WebThe program calculates the theoretical power required to drive the selected hull form through calm water at the required speed. GR = number of revolutions the crankshaft needs to produce one revolution of the prop shaft. Boat Hull. The Crouch constant depends on the *type of boat. However, because boats vary widely due to a number of factors, it is not possible to guarantee which specific prop will perform best in any specific boating application. Armor Penetration Calculator. Pontoon Hull (2 pontoons) Pontoon Hull (3 pontoons) Inshore Fishing Hull. Use the CalcT button to figure the theoretical speed from the actual speed and slip. WebSpeed = Miles/hour Obtain speed data from a radar gun if possible, boat speedometers are notoriously wrong. A new engine could throw off the balance of your boat. Enter your maximum achieved RPM 4. If the percentage shown is greater than 20, there is typically room for improvement by switching to a different propeller, adjusting drive height, etc. Use this appliance depreciation calculator to find out the current value of home appliances. Obtain speed data from a radar gun if possible, boat speedometers are notoriously wrong. All of these calculations and conversions are done for you internally in the RBBI Prop Calculator. Step up in performance with a prop thats hand finished and fine tuned from a raw stainless steel casting with perfectly matching cup heights and a custom blade thickness profile. In other words, the displacement of a boat is its weight. However, as you do this, you should increase your RPMs by approximately 200 for each 1 reduction in pitch (until the maximum RPM rating is reached). All you need to do is give any of these 4 variables as input and click on the calculate button that gives you answers in seconds. And also we are providing steps to calculate the boat propeller manually. WebPropeller Size Calculators: Planing Hull Propeller Sizing Calculator (generally applies to power boats with no keel) Displacement and Semi-Displacement Hull Propeller Sizing Calculator (generally applies to boats with keels) Minimum Propeller Diameter Calculator (good for checking the propeller diameter against the hull size) Of course, most boaters will want something that is in between good hole shot with acceptable top end speed. All you need to do is give any of these 4 variables as input and click on the calculate button that gives you answers in seconds. The speed of the boat, in simple words, is how fast it can go. Please do not include your outboard(s). This calculation is older and not as accurate. Aluminum Hull. PP is the blade pitch of propeller (inches). May 01, 2019 By In-Fisherman. This calculator is fornon-commercial useby the general public only. Propeller Calculator: MPH The calculated value is indicated by the shaded heading in the table. Speed = square root of ( 50 hp/800 lb) X 150 Speed = 37.5 mph In a pinch you can work this out on your own with a pen and paper. google_ad_height = 250; Be sure to take a look at the Prop Slippage for an explanation of how to find your prop slip. Enter the pitch of your current propeller The Propeller Slip Calculator can be used to calculate two important numbers - Propeller Slip Range and Desired Propeller Pitch. Youll also need to include Crouchs constant which varies based on the kind of boat were talking about. Step 4: Using the Crouch's formula: S = (P / D) * C = (3000 / 6800) * 220 = 146.13 mph boatspeedcalculator.com hosts a calculator that can be used to calculate the speed of a planing boat in planing speed region. Sports & Hobbies. By completing the following fields you can determine the theoretical maximum speed of your boat / boat engine. If you wonder how fast a boat can go, this calculator will help you answer that. google_ad_client = "pub-1494719669027267"; It does all the work for you with just a glance. However, it is hard to tell whether your RPM level is the best your engine can do or if it is being capped by the engines rev-limiter (to protect the engine). The calculations and results are based on imperical data and formulas. Note: The formulation and value for the Crouch constant are specific for units such as the speed is in miles per hour and displacement is in pounds. WebSpeed = Miles/hour Obtain speed data from a radar gun if possible, boat speedometers are notoriously wrong. The constants have been developed from experience, and are as follows: The constants above are from close to 20years ago. Alternatively, you can also run this calculator backwards to know how much horsepower I need for my boat to achieve a certain speed. WebThis calculator is free to use as often as you wish. For instance, a modern US navy Gerald R Ford-class aircraft carrier displaces about 100,000 tons at its full load whereas a 17th-century fishing boat displaced only about 13 tons. Step 3: Choose the Crouch constant, C from the list for hydroplanes, i.e., C = 220. ! (Overall Rating: 10), Excellent high-end Pontoon Boat with a 400hp R Mercury outboard Racing motor. google_ad_type = "text_image"; The formula for the top speed of a boat is used by designers to perform preliminary design analysis of the hulls. Webboatspeedcalculator.com uses a modified Savitsky method to calculate boat's resistance (R) and AEW propeller series data to calculate a propeller thrust (T). WebIt can also be used to calculate the propeller slip, propulsive efficiency and engine power output. WebThe program calculates the theoretical power required to drive the selected hull form through calm water at the required speed. Miles per Hour Calculator. This calculator allows you to calculate a bass fishing boat's speed. Lets take a look at what you need to know. To increase acceleration, consider reducing your pitch. Outboard Propeller Information Center Propeller Handbook : The Complete Reference for Choosing, Installing, To use the calculator, input four of the five variables. Some of our partners may process your data as a part of their legitimate business interest without asking for consent. 4. Or, more likely, google_ad_format = "300x250_as"; Required fields are marked *. All rights reserved. Engine RPM = rev/min
You may find it when you Google boat speeds and wonder why the different formulas exist. A license for commercial use may be available upon application to BAM Marine on a per use or annual basis. For instance, if the propeller moves forward 15 inches every time it completes a full turn, the nominal propeller pitch is 15 inches. Engine RPM: Usually between 5000 - 6000. Youll need to know a handful of factors when calculating boat speed. The hull and transom are meant to support only a certain amount of pressure and weight. Plus, what if you want to know before you get on the water? WebThis calculator is free to use as often as you wish. By clicking below to subscribe, you acknowledge that your information will be transferred to Mailchimp for processing. Simply give the inputs in the input fields and click on the calculate button that gives you the answer effortlessly. The propeller revolution rate is determined by dividing the engine rpm by the gear ratio. Even if you never need to write it out by hand. This property of a ship is an application of Archimedes' principle. Select one of the pitch calculation methods below, then click "Find Propellers" to search for your ideal propeller. Web1. This allows you to get a better idea of how long any trip will take, how much weight your vessel can carry, and more. Choose the precision-tuned performance of a Mercury Racing Pro Finished model or the race-spec perfection of a Mercury Racing Lab Finished propeller. Here is a way to calculate prop performance with different props, a formula suggested to us by technician Peter Arneson: Props slip, so they're about 85 to 90 percent efficient. WebTo use our boat prop calculator, you need four inputs: RPMs: Revolutions Per Minute. This one here is really more something you should be aware of. Aluminum Tiller. The Square Root of (Total Shaft Horsepower / Weight ) x Constant = Speed. If an accident occurs your insurance company may deny a claim. (a 15 inch pitch prop theoretically propels the boat 15 inches in one revolution). Aluminum Hull. This is why most of us dont like to calculate it ourselves. Step 4: Using the Crouch's formula: S = (P / D) * C = (3000 / 6800) * 220 = 146.13 mph