how to measure transom height for outboard motor

This website uses cookies to improve your experience while you navigate through the website. However, you will need an understanding of how the degrees will alter the boats usability. Variables to consider when determining the mounting height include the size and style of the boat and the length of the outboard motor's shaft. You also might not be able to lift the outboard out of the water entirely for storage. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. Most of the time, adding a hydrofoil to an outboard improves performance. It is extremely important that the boater understands the significance of the transoms height. 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. There are 2 steps to help get a relatively accurate figure. The height of the transom is estimated by using the center line to measure from the bottom of the hull to the top of the transom. The transom angle is the vertical incline of the transom and is measured in degrees. Or measure from the main engine prop up to the water line? To achieve this, the motor itself has to be attached at the correct height. steel ruler, etc. For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. var ptScript = "https://cdn.paytomorrow.com/js/pt-mpe.min.js"; 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. Outboards designed for saltwater applications usually have longer shafts. The transom is the flat vertical section at the rear of the boat. The height of the boat transom dictates the size of the outboard motor. var interval = setInterval(function () { Although the longer outboard shaft length can lead to lower speed and more drag, the boat can push a heavier load. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. It is extremely important that the boater understands the significance of the transoms height. You also have the option to opt-out of these cookies. 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. If you have a question or need additional information,contact ustoday. All rights reserved. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. mpeSelector: ".pt-mpe", https://www.bornagainboating.com/Get Your Born Again Boating Clothing! Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? No one wants to have issues with a new transom or boat repairs. var h = d.getElementsByTagName("head"), As a dealer I run into this situation from time to time, which is fine but getting the right length outboard for your boat is crucial. See When St. Peters Basketball Games Are Today! Other factors to consider when determining the mounting height of an outboard are related to performance. This was the height of my 225 Yamaha on my TR21 s.setAttribute("type", "text/javascript"); Brackets are also handy for boats that do not have flat transoms, like canoe-stern sailboats or fan-tailed motor vessels. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. Some boats are equipped with transom-hung outboards while others have a bracket. If the propeller fails to ventilate, the motor is mounted to low. maxAmount: 6500.0, However, there may be times when a boater strays away from these recommendations. Ill also explain the difference between short and long shafts and how they vary by type of boat. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. (127 mm). The distance between the ends of a transom is measured in inches. Beginning boaters should be aware of the boats measurements. For slower boats, its less critical to. How do you measure a transom on an outboard motor? Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. Its still smart to measure it yourself though, just in case, the design changed over the years. Usually speaking, the farther the outboard is set off the transom, the higher the propeller should be in the water (or the higher the outboard can be mounted). As a yacht designer and boater, I prefer longer shafts. We also use third-party cookies that help us analyze and understand how you use this website. 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. The greater the number, the more the drive may sway (also called tuck under or negative trim). 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. 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. The propellers will also have trouble reaching the water. 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. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. Boats that use longer outboard shafts include: The lowest point will likely be directly under your drain plug if youve got one. Extra-long shafts are 25-inches long. Look at the part of your motor that would be There are also specialty motor shaft lengths. This is also known as the shaft length. A yardstick will help you determine if your outboard engine is at the right height. Here we will guide you in how to get the right boat transom height. 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. The first order of business is to measure your boat for the ideal fit. Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. The cookie is used to store the user consent for the cookies in the category "Analytics". To achieve this, the motor itself has to be attached at the correct height. How Transom Height Is Measured For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. Using your existing control box and gauges will save you quite a bit of money in the end. Or it can have an angle degree as high as 30. <> 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. The standard installation of an outboard has the top of the transom of the boat at the same level as the bottom of the motor portion of the outboard. If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. Gear case sits just below or at the hull depth due to the deep v. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. You may wonder how deep your prop should be in the water. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. Once you know what will fit on your hull, you can fine-tune your choice based on the performance youre looking for and how you use the boat. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. Learn More About Your Boats Systems By Joining The Born Again Boating Academy! If you have an outboard motor, the distance from one end to another will be found on the side or on a label near its bottom. What's the best height for my boat motor? var BCData = {"csrf_token":"d7ecb6b56891bb66aee12dbc01a80162b3ed582c1acbe30f16fc9f1b2abc362f"}; It can also improve the experience of driving a faster boat. % endobj d.addEventListener("DOMContentLoaded", function (e) { 5/rC,aQhsK@Q. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. It is extremely important that the boater understands the significance of the transom's height. 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. 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. You run the risk of possibly unsafe handling if you attempt to put a long shaft engine on a transom designed for a short shaft engine. %PDF-1.7 For over five years he has worked as a newspaper reporter and historic researcher. If possible for your peace of mind and not let down that magnificent purchase opportunity, place that 08 kicker at back transom and test for yourself. measuring; you may have to "extend" the flat part of the No one wants to have issues with a new transom or boat repairs. (3) Move horizontally across the chart until you hit the graph curve. Raising an outboard higher on the transom can reduce drag and raise top speed. With the outboard shaft length too long, meaning the prop is too deep in the water, the engine wont be as efficient, and the fuel burn is high. It also cuts into speed and fuel efficiency. It is where the outboard is mounted, and some boat owners place the name of the boat. Typical motor lengths include the following. In lower mounting, the engine is set lower than the recommended standard. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Tilt your motor until the bullet of the gearcase is straight edge on the top of the transom to "extend" it out Another important measurement is the transom angle. Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. (function () { Where Onboard a Boat is the Transom Located and More About Transom Heights A propeller operates based on the height of the transom. If your outboard motor height. 1 0 obj Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. You dont have to be a mathematician to determine the correct boat transom angle. What Kind of Fuel Does Your Marine Engine Need? This measurement would be the inches of Most of the standard engined boats it takes shafts that are 15-30inches long. Some fishing boats can handle the motor being underwater. Among them will be first-timers or those who have recently purchased their boats. function gtag(){dataLayer.push(arguments);} Necessary cookies are absolutely essential for the website to function properly. Here we will guide you in how to get the right boat transom height. 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. A reversetransom that sits too high can impact the propellers of the motor and motor bracket. If you go too short your more than likely going to cavitate and loose power. This alone can outweigh the negatives when deciding to adjust the mount upwards. Place the point of a yardstick at the middle of the top of the boat transom. ), Al Shields Actually there is no designated letter for short shaft. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ The boat transom can be flat with zero degree angles. The pressure behind your hand dropped as you slid your hand back and forth through the water. An outboard motor can drive just about any sort of boat with proper mounting. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. of the motor off the transom Other boats that need extra long shafts are: Read my other articles on outboard motors. The average transom angle is around 14 degrees. Each one has a totally different effect on the boats performance. Extra-extra long shafts are 30-inches long. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. "brackets". This measurement was approximately 4". I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. Place the rulers end on the ground behind the club and let the club to rest on top of it. Among them will be first-timers or those who have recently purchased their boats. Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" To measure the transom height, measure from the center on for transom (rear of the boat). (616) 364-0666, On all contiguous US part orders over $100. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. Higher mounting decisions should be left to the professionals. The height of the transom is calculated by measuring from the bottom of the hull to the top of the transom, using the center line. Place the bracket on the transom to the left of the main outboard or rudder. primeApr: 12.99, This is a measurement that has been used for BassCats, I'm If youd like to see this in video format, skip to 0:44 in the below YouTube Video: Is it OK to put a long shaft outboard on a boat thats rated for a short shaft? document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; Check out the full chart of the Mercury outboard model code and its features. maxMicroAmount: 0.0, This will be the 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. The height of the transom is calculated by measuring from the bottom of the hull to the top of the transom, using the center line. Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. He is a The average transom angle is around 14 degrees. According to MarinePartsMan.com, the outboard can be raised 1 inch above the standard height for every 10 miles per hour of speed the boat can attain. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Some outboards have a serial number that tells you which shaft length to go for. You can use a longer shaft than recommended and your boat will work fine. Having the cavitation plate a bit lower than the transom is preferable to having it too high. When fighting waves from the stern, a 20-inch transom is considerably safer. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Whats the best height for my boat motor? Figuring out how to measure motor height on a Cavitation plates are used on the bottom components of boats to help them operate better. 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. Industry standards dictate that for short shaft engines the transom height should be 15. Again, make sure that you are measuring to the flat part of the brackets; The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. The boater must also consider if the boat transomsupport is designed to bear the weight of a higher mount. Expectedly, when the transom angle is zero, it means it is flat. 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. bracket forward with a straight edge to where you can then measure up 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. displayMicroOffers: false, When it gets to the short side (14), When the inner corner of the square comes into touch with the transom, measure the distance between the inside corner of the square and the boat bottom (see drawing below). Doing this can have adverse effects. If you said something smaller than that, thats where it can get tricky. A big NO. According to MarinePartsMan.com, the outboard can be raised 1 inch above the standard height for every 10 miles per hour of speed the boat can attain. This, however, is not recommended for the beginning boater. 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. 2 0 obj At least if its too long you can raise the motor or "build up" your transom. the propshaft below or above the pad. Increased RPM and additional horsepower feed the need for speed. This would not be a good thing. Follow Westshore Marine & Leisure on Twitter! If mounting directly to a boat transom: Measure from the top of the transom down to the bottom of the hull or keel (lowest point). As with anything, there are exceptions to the rule. If the height of the boat transom is off it can cause major issues. Then, you can pick the right engine. The height of the boat transom dictates the size of the outboard motor. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Any owner seeking the last bit of speed from an outboard-powered boat should grab a yard stick. You dont have to be a mathematician to determine the correct boat transomangle. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. So how to measure outboard shaft length? Read the following to get the optimal shaft length for outboard motors! My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. parallel with the straight edge. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. You must be still in the blue about that matter. The outboard comes with mounting holes and brackets. All you need to do is measure how much to rise. I mean it is better to be safe than sorry, am I right? They keep water out of your prop and increase water pressure in the system. This cookie is set by GDPR Cookie Consent plugin. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? Actual shaft length is 21.5" on those. s.setAttribute("rel", "stylesheet"); As summer approaches there will be more boaters taking to the water. storeDisplayName: "Marine Parts Warehouse", Boaters who consider going with a higher mount can see increased speeds. There is a simple test to see if your outboard motor is set at the best height. Take a long straight edge, (long carpenter's level or long This distance is very important to the performance of you boat. Measure the area of the transom directly where the engine will be mounted. The motor is what powers the boat so the two go hand-in-hand. Repowering your boat is one of the most expensive upgrades you can make. On the downside, a higher mount can interfere with the boaters steering capabilities. var prefix = 'ma' + 'il' + 'to'; Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. When you measure the width of the stern, mark the center with a grease pencil. However, the motor should not be raised more than 5 inches above the standard position. s = d.createElement("link"); However, your boat will have slightly more drag which will reduce your maximum speed. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. With some boats I have a pretty good idea as to what length motor should be hung on them. This cookie is set by GDPR Cookie Consent plugin. Then open up the clamp bucket. In the case of a dinghy or johnboat, this point may be the top of the transom. This also means it can affect the safety of the boat. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. Determining Your Boat Transom Angle The transom angle - commonly measured in degrees - is the transom's vertical inclination. Copyright 1999-2023 Boats Group. It can also improve the experience of driving a faster boat. Why wont Touch ID be under the screen in the iPhone 15 and iPhone 16? This is the dimension you'll need to know when deciding between a short shaft, long shaft or extra long shaft for your outboard motor. If the propeller fails to ventilate, the motor is mounted to low. This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. 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}');

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