how to measure transom height for outboard motor how to measure transom height for outboard motor

Add yours in the comment and Ill get back to you asap. Two years ago, I bought a Boston Whaler to fish off the coast. This website uses cookies to improve your experience while you navigate through the website. The transom is the boats flat vertical part at the back. Having the cavitation plate a bit lower than the transom is preferable to having it too high. 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}'); The pros and cons of properly . your motor will be higher.) This is probably the worst case scenario out of the two. A big NO. maxAmount: 6500.0, If you have a short shaft motor, the distance between the top of the transom and the bottom of the boat should be between 15 and 16 inches. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. 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. Here we will guide you in how to get the right boat transom height. boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. In the photo above, we've measured from the motor bracket to the top of 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. This could also effect your travelling capabilities on the boat trailer. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. This, however, is not recommended for the beginning boater. The lowest point will likely be directly under your drain plug if youve got one. Will Charpentier is a writer who specializes in boating and maritime subjects. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. What are Apple Podcasts Subscriptions and Channels? The engine must be linked to the transom at the proper height for a propeller to best meet specific boating demands. A2: Instead of changing to the short outboard shaft, you can try the Jack Plate first. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. An inch or two probably wont make a big difference, but any more than that will lead to trouble. This is a measurement that has been used for BassCats, I'm 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. height (that I'm aware of); probably the most common is: A deep Vee hull will result in a different measurement than a flatter . You may wonder how deep your prop should be in the water. priceSelector: ".price--withoutTax, span.price.price--withTax", Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. 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. The amount of degrees the transom leans back from vertical is known as the transom angle. The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. Learn More About Your Boats Systems By Joining The Born Again Boating Academy! Whether you already own a boat or looking for your first watercraft we are here to service your needs. However, your boat will have slightly more drag which will reduce your maximum speed. Ill also explain the difference between short and long shafts and how they vary by type of boat. Hold the tape on the top, center of the taffrail and measure straight down to the point, usually a sharp angle, where the transom joins the bottom of the boat. This is simply a measurement taken from the top of the transom (top of Picking the right shaft length is mostly a factor of the transom height or the back of the boat. manufacturer will recommend the outboard height according to the bracket shape and length. If your outboard motor height. For vee-shaped hulls, the lowest spot of the hull will come to point, while on flat-bottomed boats it will be more or less level. It also includes attaching the right engine. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. Another important measurement is the transom angle. Then finally test your outboard, if the mount is perfect. So how to determine the outboard shaft length? debugMode: false, Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. Increased RPM and additional horsepower feed the need for speed. Its where the outboard motor is attached, and its also where some boat owners put the boats name. When fighting waves from the stern, a 20-inch transom is considerably safer. Sluggish speeds, poor handling, heavy spray, porpoising, or even water pushing up into the cowling are all signs that an outboard is set too low. You can use a longer shaft than recommended and your boat will work fine. "brackets". The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Copyright 1999-2023 Boats Group. This exhaust port should be about 1 inch above the water line when the boat is idling. Among them will be first-timers or those who have recently purchased their boats. % 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. 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 could also affect your travelling capabilities on the boat trailer. I would ask you to go back and measure the transom of your boat. In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. Tightening Torque for Engine. Why wont Touch ID be under the screen in the iPhone 15 and iPhone 16? Your email address will not be published. (1) Multiply the overall length of your boat (in feet) by it's widest beam at the stern (excluding any Fins and or Shear) (2) Locate that value on the left hand vertical column of the chart below. if (PayTomorrow) { The first order of business is to measure your boat for the ideal fit. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. So in hopes that this will help out some new boaters this spring, here's a little rundown on outboard shaft sizes and how to figure out which one you actually need. not sure that it's still used. This cookie is set by GDPR Cookie Consent plugin. since 1986. How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. Required fields are marked *. This cookie is set by GDPR Cookie Consent plugin. Measure straight down to the lowest point on the hull. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. bracket. Read the following to get the optimal shaft length for outboard motors! In lower mounting, the engine is set lower than the recommended standard. However, youll notice a little increase in drag and a decrease in top-end performance. Beefier jack plates can be fitted should a boater be looking to mount an outboard with a shorter shaft than their transom demands. The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. If it measures 15" or with in a inch of that you will need a short shaft outboard. Theyre also useful if the back of your boat has a non-standard measurement. 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. What's the best height for my boat motor? 4 0 obj If you have a jackplate, you may have to get a bit creative in your If you go too short your more than likely going to cavitate and loose power. For over five years he has worked as a newspaper reporter and historic researcher. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. stream We also use third-party cookies that help us analyze and understand how you use this website. When you measure the width of the stern, mark the center with a grease pencil. However, there may be times when a boater strays away from these recommendations. So how to measure outboard shaft length? Each one has a totally different effect on the boats performance. Step 2: Three Variables to Consider function gtag(){dataLayer.push(arguments);} The anti-cavitation plate above the prop needs to be within an inch of the bottom of the transom, therefore, the prop should be well below the transom. Long shafts are 20-inches long. With a jack plate, you can mount it exactly where you want it. minAmount: 300.0, var h = d.getElementsByTagName("head"), MPW eBay Store - Thousands of New OEM Old Stock Parts! This is measured by the propeller shaft being parallel to the vessels bottom. x\[D~OUCO6[j](l%ay <8cylY{.L2s#]~U6A|Wj]-oo|mubqY6wbY_|!>Z8(RB:RHeTzOGO_=~t\ Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Actually there is no designated letter for short shaft. And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. jackplate to a point level with the top of the transom. 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. storeDisplayName: "Marine Parts Warehouse", This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). 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). var xmlHttp = new XMLHttpRequest(); Pad to bottom of As mentioned above, the operation of the propeller relies on the transom height. hulls, such as Allisons, Bullets, Strokers, etc., this measurement could 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 mounting height of an outboard motor can impact the speed and handling characteristics of the boat. 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. 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. ensure that your measurement is accurate. 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. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. bassboat can be a bit confusing at times; hopefully this will help sort As a dealer I don't really like hearing this because there is a chance it could go either way and you have to get it right. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. This distance is very important to the performance of you boat. Gear Oil Quantity 195ml(6.6 Fl.oz.) A reverse transom that sits too high can impact the propellers of the motor and motor bracket. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. up to the bottom of the motor brackets, (as in #1). Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. Industry transom height standards have been evolved during the last 30 years: 15 for short shaft engines, 20 for long shaft engines, and 25 for extra-long shaft engines. xmlHttp.setRequestHeader('Content-Type', 'application/json'); If you have a fast boat, getting the outboards cavitation plate at the same level of the hull will ensure quick hole shot and fast top-end speeds.