how to measure transom height for outboard motor

If you are looking to repower, they may be able to offer some sage advice. This cookie is set by GDPR Cookie Consent plugin. Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. (Any measurement given as "off the transom" If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. (function (d) { stream Analytical cookies are used to understand how visitors interact with the website. The transom is the rear wall of the boat where the outboard engine is mounted in the middle. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. function loadScript(script) { His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. The propellers will also have trouble reaching the water. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". Lubrication System Engine Oil Mixed Gasoline. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. This cookie is set by GDPR Cookie Consent plugin. With the motor trimmed so that the propshaft is parallel to the keel, the anti-ventilation plate should be just about even with your straight edge, and thus even with the boat bottom at the keel. on How to Measure Outboard Shaft Length: The Only Guide You Need, ePropulsion vs Torqeedo: An All-Round Comparison, 55 lb Thrust Trolling Motors: All You Need to Know Before Purchase, Spot Lock Trolling Motor: Is It Worth It & Best Options in 2022, Wiring 24V Trolling Motors: 24 Volt Wiring Diagram (with Video), LiFePO4 Battery: Why Lithium iron Phosphate Batteries Are Your Best Options in 2022, Minn Kota vs MotorGuide: Best Option in 2022. Also, how do you determine the length of an outboard transom? trimming the motor out by one-half to full trim. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. Place the point of a yardstick at the middle of the top of the boat transom. Doing this can have adverse effects. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. There Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. The shaft length for outboard motors has nothing to do with the water line. The cookie is used to store the user consent for the cookies in the category "Performance". resting on the transom if you had the motor all the way down on the boat Outboards designed for saltwater applications usually have longer shafts. Required fields are marked *. If youre going the other way around and trying to figure out how long the shaft on your outboard is, measuring it is equally easy. up to the bottom of the motor brackets, (as in #1). These two measurements will give you the length of the shaft you need. 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 engine may be lifted one inch for every eight to ten inches of distance between the transom and the prop, according to a boat riggers rule of thumb. displayMicroOffers: false, would be more accurate.) #1: Height 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. Copyright 1999-2023 Boats Group. Basically, there are three main ways to measure motor height (that I'm aware of); probably the most common is: # 1: Height of the motor off the transom This is simply a measurement taken from the top of the transom (top of the aluminum plate on top of the transom), to the bottom of the motor "brackets". Expectedly, when the transom angle is zero, it means it is flat. 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. In the case of a larger offshore boat, it may be to the top of a cutout on the . Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. <>/Metadata 127 0 R/ViewerPreferences 128 0 R>> Brackets are also handy for boats that do not have flat transoms, like canoe-stern sailboats or fan-tailed motor vessels. Boaters who consider going with a higher mount can see increased speeds. Get the latest updates on new products and upcoming sales, 2023 Marine Parts Warehouse Incorporated disregard the downward pointing "hooks" at the front of the It is where the outboard is mounted, and some boat owners place the name of the boat. }) } }); })(document); and I'll explain it better, (or point you to someone that can help. 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. xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); h[0].appendChild(s); This is a measurement that has been used for BassCats, I'm The general guideline for longer shaft outboards is that the transom height should be at least 20 inches (50,8cm) above the waterline. Will Charpentier is a writer who specializes in boating and maritime subjects. If your boats transom height is 15-16, a short shaft engine is required, and if it is 20-21, a long shaft engine is required. hulls, such as Allisons, Bullets, Strokers, etc., this measurement could Having the cavitation plate a bit lower than the transom is preferable to having it too high. You dont have to be a mathematician to determine the correct boat transom angle. And the rule of thumb is that you should keep the cavitation plate level with the bottom or keel of the boat. } Check out the Westshore Marine & Leisure google plus page! You reply, "Im not sure, I think its a long". Industry standards dictate that for short shaft engines the transom height should be 15. A big NO. since 1986. Take the center measurement from the top to the bottom of the hull. Extra-long shafts are 25-inches long. Simply start with the engine in idle, followed bytrimming the motor out by one-half to full trim. Assistant Measuring tape Grease pencil 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. 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. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. Another important measurement is the transom angle. How Transom Height Is Measured Owners of bass boats, RIBs, or offshore fishing boats need to get this right. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. The propellers will also have trouble reaching the water. s = d.createElement("script"); This is measured by the propeller shaft being parallel to the vessels bottom. Always weigh the risks of making adjustments. Some may call it a standard length while others may call it a short or a long shaft. Another important measurement is the transom angle. Gear case sits just below or at the hull depth due to the deep v. Bass boats, ski boats, or center cockpit vessels will want to double-check their measurements to get it just right. Ten years ago I bought my first boat. 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. This alone can outweigh the negatives when deciding to adjust the mount upwards. With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. ), Al Shields Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. bracket forward with a straight edge to where you can then measure up It varies between different motors and boats. If it measures 15" or with in a inch of that you will need a short shaft outboard. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. Next, measure from your centerline to where the outboard will be mounted on each side. #3. Step 2: Three Variables to Consider 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. Not to measure boat speed, but to gauge the mounting height of the outboard motor on the boat transom. 7. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. 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. Follow Westshore Marine & Leisure on Twitter! This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. As with anything, there are exceptions to the rule. Later in the article is an image that shows you exactly where to measure. Among them will be first-timers or those who have recently purchased their boats. 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). If you are running a twin-engine setup, then measure the same distance from each clamping plate to the bottom of the hull. 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. All boats are different, and the motor manufacturers produce a variety of standard lengths. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; If the propeller fails to ventilate, the motor is mounted to low. If it measures 15" or with in a inch of that you will need a short shaft outboard. Most of the time, adding a hydrofoil to an outboard improves performance. 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. I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) There is a simple test to see if your outboard motor is set at the best height. Safely but briskly accelerate. Tightening Torque for Engine. steel ruler, etc. The same is true for the newest, high-powered offshore fishing boats, where triple or quadruple motor setups are becoming more and more common. Take a long straight edge, (long carpenter's level or long This is simply a measurement taken from the top of the transom (top of It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. If you have a question or need additional information. All things considered, sticking with the industry standard is best for the beginner. You can use a longer shaft than recommended and your boat will work fine. It was a 23-foot Crestliner Grand Cayman pontoon boat. a Detwiler manual jackplate. On this type of boat, if you are in doubt, default to the longer-shafted outboard. Other factors to consider when determining the mounting height of an outboard are related to performance. Each one has a totally different effect on the boats performance. Before we get started lets see what a boat transom is and what it does. Engine Oil Type Genuine or Recommended 2str Engine Oil. 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? The transom is the "back wall" of your boat, the most rearward part of your hull. The faster your boat, the more critical it is to get the sizing just right. The amount of degrees the transom leans back from vertical is known as the transom angle. At least if its too long you can raise the motor or "build up" your transom. It does not store any personal data. var interval = setInterval(function () { You can find your Mercury outboard model code on an ID plate or sticker. Measure straight down to the lowest point on the hull. Mounting the outboard motor in accordance with the industry standards is important. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. Doing so, will put the propeller right below the boat. In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. 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. Check out some hot FAQs to help you get the proper outboard shaft lengths. With some boats I have a pretty good idea as to what length motor should be hung on them. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. If the propeller fails to ventilate, the motor is mounted to low. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. The vertical distance between the interior of the clamp and the cavitation plate is the shaft length specified by the outboard manufacturer. loadScript(ptScript); An outboard motor can drive just about any sort of boat with proper mounting. How do you measure a transom on an outboard motor? from the transom. The first order of business is to measure your boat for the ideal fit. center of the propshaft. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. 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. 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. Plus, a low transom cut is an invitation for the water to flood the boat. motor brackets While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. This, however, is not recommended for the beginning boater. MPW eBay Store - Thousands of New OEM Old Stock Parts! if (PayTomorrow) { Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Learn More About Your Boats Systems By Joining The Born Again Boating Academy! Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. Anything bigger than that your obviously going to need an extra long shaft. Ill also explain the difference between short and long shafts and how they vary by type of boat. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. AztH ^zv_ cT,E1K/rAB54| The transom angle is the vertical incline of the transom and is measured in degrees. How the outboard will sit on the back of the boat depends on how the transom is designed. measuring; you may have to "extend" the flat part of the Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. To break it down a bit more for you: Short shafts are 15-inches long. 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. var addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@'; Safely but briskly accelerate. These cookies will be stored in your browser only with your consent. What types of boat need an extra long shaft? Or measure from the main engine prop up to the water line? 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. 12 Small Fishing Boat Accessories to Buy Today. However, youll notice a little increase in drag and a decrease in top-end performance. Be sure to measure carefully and research thoroughly before diving in. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. There is a simple test to see if your outboard motor is set at the best height. Most of the standard engined boats it takes shafts that are 15-30inches long. Beefier jack plates can be fitted should a boater be looking to mount an outboard with a shorter shaft than their transom demands. enableMoreInfoLink: true, storeDisplayName: "Marine Parts Warehouse", 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. Tilt your motor until the bullet of the gearcase is Actual shaft length is 21.5" on those. Read the following to get the optimal shaft length for outboard motors! Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. straight edge on the top of the transom to "extend" it out 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. (616) 364-0666, On all contiguous US part orders over $100. Before we get started lets see what a boat transom is and what it does. Then open up the clamp bucket. The average transom angle is around 14 degrees. 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. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. In lower mounting, the engine is set lower than the recommended standard. publicId: "32bf3437d1346295e03ebcf545f9c839", 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. 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. Outboard Motor Shaft Length: How do I measure? What are Apple Podcasts Subscriptions and Channels? This could also effect your travelling capabilities on the boat trailer. Then finally test your outboard, if the mount is perfect. 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. 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. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. 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 decreases the boats lift and increases the time it takes for the boat to reach plane. The brackets can add 1 inch to the overall mounting height of the outboard. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; You'll need a short shaft outboard if it's 15 or less than an inch shorter. Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. Look at the part of your motor that would be

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