A final note you might want to consider if youre looking to soup up your boat. John Loo 2017-08-13T21:34:25-07:00 Share on: Page load link A number of factors affect how much horsepower is ideal for your boat. To increase acceleration, consider reducing your pitch. Parts, Inflatable Hardware, Boat Seats by Boating Tackle Resources Info Search Boat Horsepower Calculator Use this Boat Horsepower Calculator to estimate the power required to efficiently move your skiff. In fact, every boat is required to have a maximum horsepower rating. A boat propeller has two basic dimensions: diameter and pitch. boatspeedcalculator.com is a private project started in 2021 by a marine engineer who works. 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. This equals 115 miles or 185 km. Step 4: Select the Model of your engine. 1) 7600 x 1.37 = 10,412 rpm at the prop 2) Convert 10,412 revolutions per minute (RPM) to revolutions per hour by multiplying x 60 (60 minutes in one hour) 10412 x 60 = 624720 revolution per hour Plumbing, Anchor 2.43 x the square root of the waterline length in meters. Downs, Couplers, Mounts, Thanks For the formula. JavaScript is disabled. The calculator can also compute any one parameter from the other three parametersa most useful feature. Systems, Marine Plumbing Enter Gear Ratio. Then, decrease the pitch by an inch or two. That can be fun if you do it safely and, of course, safety is the number one concern. JavaScript is disabled. Use this calculator to figure out just about anything in regard to propeller, ratio, RPM and speed. ! (Overall Rating: 10), Excellent high-end Pontoon Boat with a 400hp R Mercury outboard Racing motor. The speed of the boat, in simple words, is how fast it can go. Choose the precision-tuned performance of a Mercury Racing Pro Finished model or the race-spec perfection of a Mercury Racing Lab Finished propeller. GR is the number of revolutions the crankshaft needs to produce one revolution of the prop shaft. Learn more about Mailchimp's privacy practices here. Example of using the boat speed calculator. What Happens When a PWCs Steering Control is Turned to the Right? If you need to buy a new engine you can calculate the horsepower using the same formula. The waterline length is measured in feet while the boat speed is calculated in knots. Hitches, & (a 15 inch pitch prop theoretically propels the boat 15 inches in one revolution). Basic Prop Calculator. Boat Propeller Calculator You can use this boat propeller calculator to determine one of five variables: boat speed, propeller slip, propeller pitch, engine gear ratio, or engine revs. Anybody have any reasons why that wouldn't get you at least in the ballpark? what our members are saying about their boats, This boat gives you a fast, dry, and smooth ride. (Overall Rating: 10), Wide beam and large cockpit. 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. but i don't fully understand how to use it correctly for calculations, Jon and V boat Conversions and Modifications, 1967 Starcraft Seafarer - 1986 Evinrude 40hp, Advice and ideas on decking out our Tracker Guide v14, 1986 Evinrude 40 Tiller, How to wire fuel primer solenoid. See our Prop Folder for additional information about propellers. Copyright 2023 by BAM Marine of Florida Inc. Learn more about Mailchimp's privacy practices here. Check out 23 similar transportation calculators , Social Media Time Alternatives Calculator. If you prop your boat to maximize top speed, acceleration will be compromised and visa-versa. All the credit should go to James Hebert at continuouswave.com; I simply copied and pasted his work and included the link. Boat Repair, Boat Paint & Usually, a higher horsepower engine is also going to be heavier. I appreciate that . FORMULA TO CALCULATE PROPELLER SLIP The true speed of the boat was 45 MPH. Deals, Boat Seats Hardware, Marine Accessories, Boat Speed = Miles/hour Sockets, Marine Electrical I have been pretty persistent about this.. Drink Holders, http://www.rbbi.com/folders/prop/propcalc.htm, http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009536#000000, http://www.go-fast.com/Prop_Slip_Calculator.htm. 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. google_ad_client = "pub-1494719669027267"; The slip can be much higher at lower speeds, often above 50%. We have found manufactures published weight to be unsuitable for these calculations. Not that I've looked extensively for one but. 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. 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). Youll need to know a handful of factors when calculating boat speed. The propeller revolution rate is determined by dividing the engine rpm by the gear ratio. As such, if an engine has a gear ratio of 2:1, the engine drive shaft will turn twice for every propeller revolution. Hardware Ignition Systems Lubricants / Adhesives / Cleaners Outboard Parts Propellers / Hubs Plumbing / Rigging Specials / Clearance Safety Steering Stern Drives / Transoms . That is too bad. These dimensions are often stamped or cast right on the propeller. I also recommend Dave Gerr's Propeller Handbook. Breakers, Power Packs & Jump Fast with Yamaha 300! Vinyl, Floating Boat & Rings, Prop Nut Kits & Terminals, Marine Fuse Blocks & Tubes, Shop Always open to suggestions. V is the speed at which the boat is traveling. Rear twin electric recliners. (Overall Rating: 9), We had a lot of fun using this boat the past summer. All rights reserved. You are using an out of date browser. You may well ask what happened to the other 8.97 MPH. These blueprinted propellers feature perfectly matched blade profiles for consistent multi-engine RPM. To use our boat prop calculator, you need four inputs: All marine propellers involve a tradeoff. Forums, Find It's right hand and comes in a large range of pitch sizes. The above equation is known as Crouch's formula. Taking into accout the pitch, gear ratio, and using about 15% slip, I came up with 43 mph at 4500 rpm, which is about what my speedo says. Boat Speed = 1.34 x The Square Root of Waterline Length. Trying to propel the boat faster than this will result in enormous increasing power requirements. The Square Root of (Total Shaft Horsepower / Weight ) x Constant = Speed. The pitch indicates the distance that each rotation contributes to the extent to which the boat moves forward on each rotation. Covers, Boat Wiring & google_ad_format = "300x250_as"; PITCH, a positive number; blade pitch of propeller in inches. Its pretty simple to use the formulas. By using known values for the weight, power and speed you can come up with a more accurate constant for your boat. Obviously were into some heavy work at this point. He has quite the analytical mind when it comes to this sort of stuff. Deals, Electrical I'll post up as I experiment. Copyright 2019 IBOATS. Visit our Outboard Propeller Manufacturers and Propeller Industry Market Research Page If you wonder how fast a boat can go, this calculator will help you answer that. SPEED, a positive number; the boat speed in various units of measurement. & The calculator uses known inputs of propeller shaft horsepower (HP) and total boat weight (LBS), and an estimated hull factor coefficient (C), and from these three parameters the boat speed (SPEED) is calculated The relationship is expressed mathematically: HP SPEED = ( --- )^0.5 C LBS. Multiply mph by 0.85 to determine final boat speed. Boarding, Paddles & You can then see what effect changes to weight or power will have on top speed. If the percentage shown is greater than 20, there is typically room for improvement by switching to a different propeller, adjusting drive height, etc. Save my name, email, and website in this browser for the next time I comment. That takes you to 6.3 miles per hour, give or take. 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. Boat Gel Coat - Spectrum Color, Pumps and 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. Great article. You may find it when you Google boat speeds and wonder why the different formulas exist. Prop Selection Based on Motor KV and Cell Count Only - RC Boat Calculator. I just figure I had a fiberglass glasstream bass boat years ago with a 70 that ran 42. & Live Bait Run the boat up to full throttle and then very gradually add trim, just bumping the trim button with your thumb, and watch the boat speed. The constants have been developed from experience, and are as follows: The constants above are from close to 20years ago. There is no way to easily account for all the variables that effect the performance of a boat. Tunacious said: 170 HP is not very much. If an accident occurs your insurance company may deny a claim. Too little is a struggle that can burn your engine. That could make water enter the scuppers and soak the boat. Furniture, Boat Seat Pedestals & Here's a neat calculator that allows you to input any of the factors and calculate any of the rest:<br /><br /> http://www.go-fast.com/Prop_Slip_Calculator.htm Boatist Rear Admiral Joined Apr 22, 2002 Messages 4,552 May 14, 2005 #6 Re: Can you calculate boat speed from prop pitch and rpm?