how to measure transom height for outboard motor

We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. There are instances where a lower mount may be okay. 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. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). gtag('js', new Date()); These cookies will be stored in your browser only with your consent. 7. With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. The transom is the flat vertical section at the rear of the boat. loadScript(ptScript); What's the best height for my boat motor? I mean it is better to be safe than sorry, am I right? 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. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. The pros and cons of properly . It can also improve the experience of driving a faster boat. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". Plus, a low transom cut is an invitation for the water to flood the boat. When fighting waves from the stern, a 20-inch transom is considerably safer. Most transom savers can support up to a 150HP motor, which is sufficient for most regular boats. Before we get started lets see what a boat transom is and what it does. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. However, youll notice a little increase in drag and a decrease in top-end performance. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. As you can see, the measurement is about 2 1/2". A reverse transom that sits too high can impact the propellers of the motor and motor bracket. To achieve this, the motor itself has to be attached at the correct height. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. It also decreases the boats lift and increases the time it takes for the boat to reach plane. The average transom angle is around 14 degrees. Other boats that need extra long shafts are: Read my other articles on outboard motors. This website uses cookies to improve your experience while you navigate through the website. "brackets". Over time, Boating Hub has grown into a resource for boating enthusiasts around world. 4 0 obj document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; 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. Always weigh the risks of making adjustments. function gtag(){dataLayer.push(arguments);} Engine Oil Type Genuine or Recommended 2str Engine Oil. In the second photo, we've measure down from the top of the Detwiler Outboard Motor Shaft Length: How do I measure? Knowing how this can affect the overall operation of the boat is a factor to be considered. Any owner seeking the last bit of speed from an outboard-powered boat should grab a yard stick. 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. A hydrofoil will typically level off the ride by driving the stern up and the bow down, and will stop or considerably minimize porposing on a 16 footer with a mid-sized outboard and no tabs, for example. Setting Height of Outboard Motor - YouTube 0:00 / 0:46 Setting Height of Outboard Motor nates90 71 subscribers Subscribe 83 Share 63K views 7 years ago #boatservice #outboardmotor. Whether you already own a boat or looking for your first watercraft we are here to service your needs. 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. Ill also explain the difference between short and long shafts and how they vary by type of boat. Here we look at the effects of standard, lower and higher mounting. For example, you can have the Mercury outboard shaft length by model code. If your outboard motor height. 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. However, there may be times when a boater strays away from these recommendations. A deep Vee hull will result in a different measurement than a flatter . There are 2 steps to help get a relatively accurate figure. xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. On this type of boat, if you are in doubt, default to the longer-shafted outboard. Then test the boat and adjust the height, if necessary . the propshaft below or above the pad. Tilt your motor until the bullet of the gearcase is Increased RPM and additional horsepower feed the need for speed. If so, send me an However, you will need an understanding of how the degrees will alter the boats usability. AztH ^zv_ cT,E1K/rAB54| The transom is the rear wall of the boat where the outboard engine is mounted in the middle. A transom saver, which can change the spacing between the lower unit and the trailer, negates some of the support. The boat transom can be flat with zero degree angles. Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. All things considered, sticking with the industry standard is best for the beginner. <> So how to measure outboard shaft length? Well, raising the outboard motor can be an easy task for you. Determining Your Boat Transom Angle The transom angle - commonly measured in degrees - is the transom's vertical inclination. Then, you can pick the right engine. displayMicroOffers: false, (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. The amount of degrees the transom leans back from vertical is known as the transom angle. would be more accurate.) But opting out of some of these cookies may affect your browsing experience. 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. When the boat transom is too low, the motor could end up underwater. minAmount: 300.0, As mentioned above, the operation of the propeller relies on the transom height. Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. (function () { If you decide to make some custom adjustments we have theexperience and know-howto make it happen. Why wont Touch ID be under the screen in the iPhone 15 and iPhone 16? 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. If you go too short your more than likely going to cavitate and loose power. enableMoreInfoLink: true, For slower boats, its less critical to. Workboats, sailboats, and displacement-hulled boats fall into this category. Simply start with the engine in idle, followed by trimming the motor out by one-half to full trim. Each one has a totally different effect on the boats performance. function loadScript(script) { if (PayTomorrow) { Extra-long shafts are 25-inches long. For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. This restriction includes most fishing boats and longer sailboats. These two measurements will give you the length of the shaft you need. Before we get started lets see what a boat transom is and what it does. 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. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. A2: Instead of changing to the short outboard shaft, you can try the Jack Plate first. 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. maxTerm: 36, MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. As a yacht designer and boater, I prefer longer shafts. The how to measure the shaft length of an outboard motor is a question that many people have asked. Check out the Westshore Marine & Leisure Youtube page! On the downside, a higher mount can interfere with the boaters steering capabilities. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. Some outboards have a serial number that tells you which shaft length to go for. This, however, is not recommended for the beginning boater. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. 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). This is probably the worst case scenario out of the two. Outboard shaft length plays a crucial role in the performance of your boat. You reply, "Im not sure, I think its a long". Whats the best height for my boat motor? relation to pad If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. What Kind of Fuel Does Your Marine Engine Need? This cookie is set by GDPR Cookie Consent plugin. Measure from the top of the straight edge to the center of the front Take a long straight edge, (long carpenter's level or long The transom is the boats flat vertical part at the back. What is the Virtual Sundance Film Festival? #3. s = d.createElement("script"); The height of the boat transom dictates the size of the outboard motor. 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. Beginning boaters should be aware of the boats measurements. This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. primeApr: 12.99, As mentioned above, the operation of the propeller relies on the transom height. Analytical cookies are used to understand how visitors interact with the website. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. 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. 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. Follow Westshore Marine & Leisure on Wordpress! As with anything, there are exceptions to the rule. height (that I'm aware of); probably the most common is: This could also affect your travelling capabilities on the boat trailer. Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. 2 0 obj var h = d.getElementsByTagName("head"), your motor will be higher.) % Propshaft in Learn More About Your Boats Systems By Joining The Born Again Boating Academy! Boaters who consider going with a higher mount can see increased speeds. However, the motor should not be raised more than 5 inches above the standard position. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. It does not store any personal data. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. %PDF-1.7 1855 Alpine Avenue NWGrand Rapids, MI 49504This email address is being protected from spambots. Industry standards dictate that for short shaft engines the transom height should be 15. In lower mounting, the engine is set lower than the recommended standard. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. storeDisplayName: "Marine Parts Warehouse", Here we will guide you in how to get the right boat transom height. 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. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. 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. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. Buying a boat can be an exciting purchase. A: The short answer is Yes. It is where the outboard is mounted, and some boat owners place the name of the boat. Check out some hot FAQs to help you get the proper outboard shaft lengths. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. since 1986. 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. While this is the case there is certain saltwater motors that are extra extra long at 30. Owners of bass boats, RIBs, or offshore fishing boats need to get this right. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. not sure that it's still used. ), Al Shields Theyre also useful if the back of your boat has a non-standard measurement. 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? Shaft lengths are available in increments of 5. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. Disclaimer: As an affiliate I may earn a commission on any qualifying purchases, including those from Amazon.com, at no extra cost to you read more. (function (d) { Why Rebounding Is A Key Skill for Fouth Players To Learn, Tips For Attacking a Zone Defense as a Youth Basketball Team, Why This is a Big Deal for the Sports Betting Industry. This cookie is set by GDPR Cookie Consent plugin. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Read the measurement on the transoms bottom. The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. s = d.createElement("link"); A reversetransom that sits too high can impact the propellers of the motor and motor bracket. These cookies ensure basic functionalities and security features of the website, anonymously. These are vertically aligned so the boater can make adjustments. Allowing the propeller to pull water from underneath and push it out behind the boat. There are also specialty motor shaft lengths. Measure from the top of the transom to the bottom of the hull. With it comes a lot of responsibility and new things to learn including, Why your boat transom needs to be the right height, The pros and cons of properly mounting the outboard motor to the transom, Standard mounting is always best for the beginner, Of course, its always best to go with standard practices when choosing the, Lower mounting is not for the beginning boater, Mounting the motor lower on the boat transom, There is a simple test to see if your outboard motor is set at the best height. The distance between the ends of a transom is measured in inches. We also use third-party cookies that help us analyze and understand how you use this website. But in many cases, its a little more complicated than that alone. manufacturer will recommend the outboard height according to the bracket shape and length. } The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. 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. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. 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. Like Westshore Marine & Leisure on Facebook! Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. hulls, such as Allisons, Bullets, Strokers, etc., this measurement could Take your time and understand your boat and your entire transom. There are instances where a lower mount may be okay. 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". maxMicroAmount: 0.0, 3 0 obj If it measures 15" or with in a inch of that you will need a short shaft outboard. Bass boats, ski boats, or center cockpit vessels will want to double-check their measurements to get it just right.

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