The current measurement is the ventilation plate is about 1 1/2" above the true keel line which is about 24" in front of the motor edge. When mounting the engine, you want the cavitation plate to be 1 above the boat bottom for every 12 away from the transom. Using your existing control box and gauges will save you quite a bit of money in the end. xmlHttp.send('{"store_id":"369079","timezone_offset":"-5","timestamp":"2023-03-04T05:39:31.71020200Z","visit_id":"e2642be3-34e5-4a48-b89d-639d139834e0","channel_id":1}'); Measure from the top of the straight edge to the center of the front Ask a friend to hold one end of a measuring tape at the extreme outer edge of the top of the transom while you pull the tape across its width to the opposite outer edge to measure the "length of the taffrail," which is the width of the boat across the top edge of the stern. This is measured by the propeller shaft being parallel to the vessels bottom. The transom in a boat today is a place to hang your outboard motor. This cookie is set by GDPR Cookie Consent plugin. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ var path = 'hr' + 'ef' + '='; Here are several situations on how you should adjust the outboard shaft length: Mounting the outboard a little bit higher than the standard point could reduce drag, improve RPM at full throttle, and therefore improve speed and make it easier for the boat to get on plane. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. There are instances where a lower mount may be okay. Anything bigger than that your obviously going to need an extra long shaft. On this type of boat, if you are in doubt, default to the longer-shafted outboard. See diagram below. Its important to note that manufacturers call their models different things. As with anything, there are exceptions to the rule. A1: Broadly speaking, the outboard motor shaft length for pontoon boat, bass boat, or other larger boats should be long shaft. enableMoreInfoLink: true, However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. resting on the transom if you had the motor all the way down on the boat Or it can have an angle degree as high as 30. h[0].appendChild(s); Industry standards dictate that for short shaft engines the transom height should be 15. mpeSelector: ".pt-mpe", d.addEventListener("DOMContentLoaded", function (e) { Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). The pros and cons of properly . These are vertically aligned so the boater can make adjustments. h[0].appendChild(s); Check out some hot FAQs to help you get the proper outboard shaft lengths. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. The transom is the back of the boat where the motor is hung. However, with the outboard shaft length too short, meaning the prop is too close to the surface, the engine is likely to ventilate and therefore slip on acceleration or lose power. s.setAttribute("type", "text/javascript"); If you decide to make adjustments, please consult a marine engine dealer about the boat design. The center is the point where your outboard motor is (ideally) located. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. Doing so, will put the propeller right below the boat. When measuring the transom height, you should start from the hull's bottom at the boat's center line up to the top of the transom. Higher mounting decisions should be left to the professionals. No one wants to have issues with a new transom or boat repairs. xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); maxMicroAmount: 0.0, Not to measure boat speed, but to gauge the mounting height of the outboard motor on the boat transom. (function () { This provides seaworthiness and offers maximum protection from large seas. Rest the yard stick or another suitable straight edge along the keel on the bottom of the boat so that it makes a straight line aft to the outboard. Which Navigation Lights Does Your Boat Need? How can you figure out what your transom angle is? Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. These allow the mounting of a standard length outboard behind the transom. The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. Read the measurement on the transoms bottom. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Picking the right shaft length for your outboard is an essential step in getting the best performance from your boat. Will Charpentier is a writer who specializes in boating and maritime subjects. mpeInit(); August 9/08). Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. As you can see, the measurement is about 2 1/2". bracket forward with a straight edge to where you can then measure up Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. This is also known as the shaft length. Set the end of the tape on the outside edge of the taffrail at the center and measure inward to the inside edge of the taffrail. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. actually have the propshaft above the pad.). Move the bracket as close to the center of the transom as possible while still maintaining clearance to allow the main outboard or rudder to reach its full range of motion without contacting the kicker motor. The lowest point will likely be directly under your drain plug if youve got one. The most common percent angle is probably 12, however spec sheets for O/B and I/O boats may show 10 percent, 12 percent, and 14 degrees. s.setAttribute("href", "https://cdn.paytomorrow.com/css/pt-mpe.min.css"); If it measures between 17 and 22, you'll want to go with a long shaft motor. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. This cookie is set by GDPR Cookie Consent plugin. When the right length motor is hung on the transom of a boat, the cavitation plate (the large plate that extends out over the propeller) should be even with the very bottom of the boat. var xmlHttp = new XMLHttpRequest(); I hope this helps someone out in their search for a new or newer outboard this season. If you went too long it would still work but it may lack in performance. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Check out the Westshore Marine & Leisure Youtube page! Upstream Securitys Disruptive Telematics Technology, The challenges of scaling a cloud-based security system, OneStreams unified platform streamlines financial data management, OneStreams impact on the financial software market. If you are looking to repower, they may be able to offer some sage advice. This is probably the worst case scenario out of the two. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. straight edge from the center of the pad, but this time you're measuring So if you are measuring the outboard shaft length for smaller boats, inflatables, dinghies, sailboat or other low-speed work boats, the cavitation plate is often about 2 below the bottom. the aluminum plate on top of the transom), to the bottom of the motor If the height of the boat transom is off it can cause major issues. The cookies is used to store the user consent for the cookies in the category "Necessary". The transom is the flat vertical section at the rear of the boat. Step 4. bracket. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. While this is the case there is certain saltwater motors that are extra extra long at 30. If you are running a twin-engine setup, then measure the same distance from each clamping plate to the bottom of the hull. Make sure that you are measuring straight up, at a 90 degree angle to This transom saver will support the weight of your outboard throughout your road travel, steadily bracing it against the trailer frame to relieve your transom of the weight and impact from consistent bouncing. disregard the "hooks" at the front of the Some fishing boats can handle the motor being underwater. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. High powered boats usually only come in long and extra-long variants. Youll need a short shaft outboard if its 15 or less than an inch shorter. Selecting the Correct Size Outboard Shaft, What is the Best Outboard Motor for Saltwater, Diagnosing Common Outboard Motor Problems, Best Beginner Boats Everything You Need to Know. Since the ventilation plate & foil are burried under water it is obviously too low. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. (In the case of the faster boats.com is part of the Boats Group Network. Triton. If you said you have a pontoon or a larger style boat such as a bass boat or speed boat, I would be pretty confident in saying it needs a long shaft. #1: Height However, you will need an understanding of how the degrees will alter the boats usability. In the case of a dinghy or johnboat, this point may be the top of the transom. It is extremely important that the boater understands the significance of the transom's height. will be to the flat part; if you measure to the bottom of the brackets The boat transom height is measured from the lowest point on the keel along the center line to the spot where the outboard motor's mounting holes bracket rests. Typical motor lengths include the following. storeDisplayName: "Marine Parts Warehouse", But, how do you measure it? Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. straight edge on the top of the transom to "extend" it out If measuring an existing outboard: Measure from the inside top of mounting bracket down to anti-cavitation plate above propeller (this is the largest plate/fin directly above the propeller). The point where these measurements intersect is your centerline. Here we will guide you in how to get the right boat transom height. Lastly, knowing the year of your motor and what style of controls you have (side mount, concealed side mount, or binnacle) is also a plus because it will tell the dealer if your current controls are compatible with the motor you are purchasing. hulls, such as Allisons, Bullets, Strokers, etc., this measurement could 2019s List of the Best Recreational Pontoon Boats for Sale. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. Copyright 1999-2023 Boats Group. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. Expectedly, when the transom angle is zero, it means it is flat. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. Later in the article is an image that shows you exactly where to measure. You also might not be able to lift the outboard out of the water entirely for storage. Since the length of the shaft of your outboard is associated with the size boat, smaller engines will generally have shorter shafts. Industry standards dictate that for short shaft engines the transom height should be 15. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. center of the propshaft. But in many cases, its a little more complicated than that alone. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. Here is a picture that shows you exactly where the outboard motor shaft length stands: Usually the shaft length for outboard motors falls into the following 4 sizes: In practice, you may find the outboard motor shaft length varies among different brands and manufacturers like the Honda,Suzuki, Yamaha, Torqeedo, etc. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. Follow Westshore Marine & Leisure on Twitter! Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. var ptScript = "https://cdn.paytomorrow.com/js/pt-mpe.min.js"; The greater the number, the more the drive may sway (also called tuck under or negative trim). The faster your boat, the more critical it is to get the sizing just right. The mounting height of the outboard engine is the equivalent of the distance between the base of the motor and the top of the propeller. To measure your outboard motor shaft length, measure from the bottom of the mounting bracket where it rests on the transom to the top of the cavitation plate, this is the horizontal surface of the lower unit immediately above the propeller. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. Check out the Westshore Marine & Leisure google plus page! If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. You need JavaScript enabled to view it. endobj debugMode: false, (3) Move horizontally across the chart until you hit the graph curve. Measure from the top of the transom to the bottom of the hull. This number will likely be shorter than that for a single-engine installation since you do not necessarily measure to the point of the keel. If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. Whether you already own a boat or looking for your first watercraft we are here to service your needs. This restriction includes most fishing boats and longer sailboats. |. Raising an outboard higher on the transom can reduce drag and raise top speed. What's the best height for my boat motor? Safely but briskly accelerate. I believe 20 to 21 inches is the optimum length for a lengthy shaft. See When St. Peters Basketball Games Are Today! All rights reserved. and I'll explain it better, (or point you to someone that can help. #3. This could also affect your travelling capabilities on the boat trailer. Before we get started lets see what a boat transom is and what it does. Other boats that need extra long shafts are: Read my other articles on outboard motors. })(); Theyre also useful if the back of your boat has a non-standard measurement. Doing this can have adverse effects. The propellers will also have trouble reaching the water. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. Of course, its always best to go with standard practices when choosing thebest boat engine. This distance is very important to the performance of you boat. Your email address will not be published. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. minAmount: 300.0, the propshaft below or above the pad. We also use third-party cookies that help us analyze and understand how you use this website. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. You'll need a short shaft outboard if it's 15 or less than an inch shorter. PayTomorrow.mpeInit({ } Beginning boaters should be aware of the boats measurements. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. They keep water out of your prop and increase water pressure in the system. Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. (127 mm). If you decide to make some custom adjustments we have theexperience and know-howto make it happen. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. Any questions? loadScript(ptScript); Copyright 2017 Dealer Spike All Rights Reserved. Or measure from the main engine prop up to the water line? As with anything, there are exceptions to the rule. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) Other boats that need short shafts are: A: If you have a small boat with a 18 to 21 inch aft transom, youll most likely need a long shaft outboard. However, the motor should not be raised more than 5 inches above the standard position. Follow Westshore Marine & Leisure on Wordpress! You can order an outboard in lengths ranging from 15 inches to 30 inches, depending on its power output and possible uses. To break it down a bit more for you: Short shafts are 15-inches long. Recommended Engine Oil 2-Stroke Outboard Motor Oil. This cookie is set by GDPR Cookie Consent plugin. So if you are measuring the outboard shaft length for the powerboat, planing boat, or any boat for which the speed is the priority, take the outboard shaft length 1 to 1.5 (depending on your boat types) shorter than standard would be better. This measurement would be the inches of Sailboats use these sometimes, as well as some boaters who want to install a much smaller auxiliary motor to use in case of primary engine failure. This email address is being protected from spambots. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> However, your boat will have slightly more drag which will reduce your maximum speed. The cookie is used to store the user consent for the cookies in the category "Other. Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. With this in mind, how can I determine if my outboard has a short or long shaft? relation to pad Cavitation plates are used on the bottom components of boats to help them operate better. When you measure the width of the stern, mark the center with a grease pencil. not sure that it's still used. Cavitation is when the propeller is out of the water due to the boat forming a wake of "air bubbles" or "vapor cavities" around the prop. A: The short answer is Yes. Add the two measurements and you get 6 1/2". When the boattransom is too low, the motor could end up underwater. Then, you can pick the right engine. When the jet drive is on the motor, set the height so that the leading edge of the intake is flush with the boat bottom. function mpeInit() { If you go too short your more than likely going to cavitate and loose power. Safely but briskly accelerate. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". So you should just measure the height of the boat's transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. Step 2: Three Variables to Consider In the second photo, we've measure down from the top of the Detwiler Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. Gear Oil Quantity 195ml(6.6 Fl.oz.) Buying a boat can be an exciting purchase. since 1986. This is somewhat similar to #2, in that you are again measuring with a A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Then adjust the motor in a higher hole with a flat head screwdriver. The cookie is used to store the user consent for the cookies in the category "Performance". No matter what size of boat you are running, one of the most critical choices you can make when buying an outboard motor is the shaft length. The engine must be linked to the transom at the proper height for a propeller to best meet specific boating demands. Shaft lengths are available in increments of 5. Any owner seeking the last bit of speed from an outboard-powered boat should grab a yard stick. *The Factors indicates the adjustment affected by on your boat type, the outboard working environment, and the transom distance as discussed above. Depending on the manufacturer, size names might change. Most of the time, adding a hydrofoil to an outboard improves performance. Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. Mounting the outboard motor in accordance with the industry standards is important. You can find your Mercury outboard model code on an ID plate or sticker. If it measures 15" or with in a inch of that you will need a short shaft outboard. <>/Metadata 127 0 R/ViewerPreferences 128 0 R>> If you have already measured you transom tip to bottom to be 20", then if you place aux sdieways to central engine your available transom height will be probably 1"-1.5" " higher and work perfecty. At least if its too long you can raise the motor or "build up" your transom. Beginning boaters should be aware of the boats measurements. from the transom. So its easier and safer to communicate with the dealer with the exact measurement of outboard shaft length in order to get the right model. As mentioned above, the operation of the propeller relies on the transom height. So you should just measure the height of the boats transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. It is extremely important that the boater understands the significance of the transoms height. When fighting waves from the stern, a 20-inch transom is considerably safer. How Transom Height Is Measured Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. On the downside, a higher mount can interfere with the boaters steering capabilities. Simply start with the engine in idle, followed by, If you decide to make some custom adjustments we have the. If you are running a slower boat, the exact location of the ventilation plate is less important. You may wonder how deep your prop should be in the water. measuring; you may have to "extend" the flat part of the e-mail This is a measurement that has been used for BassCats, I'm (Any measurement given as "off the transom" height (that I'm aware of); probably the most common is: It is very versatile as it generally . Its still smart to measure it yourself though, just in case, the design changed over the years. I would ask you to go back and measure the transom of your boat. % The form of a boats transom varies depending on the manufacturer and model. <> Actually there is no designated letter for short shaft. }, 100); It is where the outboard is mounted, and some boat owners place the name of the boat. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. Required fields are marked *. The first step is to determine the height of your boat's transom. Buying a boat can be an exciting purchase. Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. The amount of degrees the transom leans back from vertical is known as the transom angle. %PDF-1.7 out the confusion. What is the Virtual Sundance Film Festival? What are Apple Podcasts Subscriptions and Channels? Step 2: After you get the transom height, add the radius of the propeller (check the user manual, and then technical drawing for the number) to calculate the minimum shaft length needed to make it work. Use the mounting bracket on the motor to know where it will sit on the boat. But opting out of some of these cookies may affect your browsing experience. Your email address will not be published. Brackets are also handy for boats that do not have flat transoms, like canoe-stern sailboats or fan-tailed motor vessels. Most transom savers can support up to a 150HP motor, which is sufficient for most regular boats. Boaters who consider going with a higher mount can see increased speeds. This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. It does not store any personal data. Plus, a low transom cut is an invitation for the water to flood the boat. This is simply a measurement taken from the top of the transom (top of To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. This alone can outweigh the negatives when deciding to adjust the mount upwards. You dont have to be a mathematician to determine the correct boat transom angle. One of the factors in determining the height of the outboard is the placement of the exhaust port on the lower unit of the outboard engine. If we run into that scenario, I would still show you the different options of motors and go over pricing, but I would also ask you to hold off and do one thing before you pull the trigger. On most newer center consoles and offshoreboat transoms might include a rear door leading to a swim platform as well as a molded setback bracket. To achieve this, the motor itself has to be attached at the correct height. Adjusting the mounting height of an outboard on the boat transom can affect performance and every boat can be different, so actual on-water testing is best. You dont have to be a mathematician to determine the correct boat transomangle. With a motor tote, the outboard and boat move as one, independently of the trailer, so there are no concerns about the boat shifting on the trailer, he says. This website uses cookies to improve your experience while you navigate through the website. Boats with extended transoms, brackets that extend the mounting bracket for the outboard motor behind the back of the boat, can use a higher outboard height.

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