how to measure transom height for outboard motor

This exhaust port should be about 1 inch above the water line when the boat is idling. Doing so, will put the propeller right below the boat. It was a 23-foot Crestliner Grand Cayman pontoon boat. How Transom Height Is Measured will be to the flat part; if you measure to the bottom of the brackets endobj Knowing how this can affect the overall operation of the boat is a factor to be considered. Whats the best height for my boat motor? A reverse transom that sits too high can impact the propellers of the motor and motor bracket. What's the best height for my boat motor? Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) A big NO. Shaft lengths are available in increments of 5. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. 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. A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. This, however, is not recommended for the beginning boater. 2 0 obj Then adjust the motor in a higher hole with a flat head screwdriver. In addition, motor totes will not harm the finish of the lower unit. Youll need a short shaft outboard if its 15 or less than an inch shorter. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. 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. Propshaft in Save my name, email, and website in this browser for the next time I comment. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. var h = d.getElementsByTagName("head"), The outboard comes with mounting holes and brackets. Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. 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. There are a series of four to six holes at the top of the bracket, and the lower bolts actually fit into slots. Or measure from the main engine prop up to the water line? Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. displayMicroOffers: false, Here we will guide you in how to get the right boat transom height. Look at the part of your motor that would be 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. Or it can have an angle degree as high as 30. 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. Again, make sure that you are measuring to the flat part of the brackets; All rights reserved. You A transom saver, which can change the spacing between the lower unit and the trailer, negates some of the support. Then finally test your outboard, if the mount is perfect. Ten years ago I bought my first boat. It is extremely important that the boater understands the significance of the transoms height. 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. parallel with the straight edge. The lowest point will likely be directly under your drain plug if youve got one. Allowing the propeller to pull water from underneath and push it out behind the boat. If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. 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). ), Al Shields It is where the outboard is mounted, and some boat owners place the name of the boat. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. logoColor: "original", publicId: "32bf3437d1346295e03ebcf545f9c839", Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. What the relationship to the pontoons is, I couldn't say. Re: Dinghy with a long shaft motor? Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. This distance is very important to the performance of you boat. Other boats that need extra long shafts are: Read my other articles on outboard motors. The outboard comes with mounting holes and brackets. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Your email address will not be published. You can use a longer shaft than recommended and your boat will work fine. Tilt your motor until the bullet of the gearcase is With more than a decade of experience cruising the lakes in my Crestliner Grand Cayman pontoon boat and my Boston Whaler, I now want to share everything I've learned with my community here at Boating Hub. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. 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. "brackets". To do so, measure from the stern (back) of the boat to the midpoint of the hull on both sides. The clamp bracket on the latest Mercury Four-Stoke-model outboards has five mounting bolt holes spaced .75 inches apart. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Extra-long shafts are 25-inches long. Add the two measurements and you get 6 1/2". and I'll explain it better, (or point you to someone that can help. #1: Height maxTerm: 36, This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. When you measure the width of the stern, mark the center with a grease pencil. s = d.createElement("script"); As summer approaches there will be more boaters taking to the water. 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. Industry standards dictate that for short shaft engines the transom height should be 15. e-mail To achieve this, the motor itself has to be attached at the correct height. of the motor off the transom 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. Two years ago, I bought a Boston Whaler to fish off the coast. The first order of business is to measure your boat for the ideal fit. In lower mounting, the engine is set lower than the recommended standard. The transom is the "back wall" of your boat, the most rearward part of your hull. They operate as a planing surface, allowing your boat to climb to the top more quickly. 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. 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. Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. This cookie is set by GDPR Cookie Consent plugin. The engine must be linked to the transom at the proper height for a propeller to best meet specific boating demands. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. 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). These two measurements will give you the length of the shaft you need. Any questions? A reversetransom that sits too high can impact the propellers of the motor and motor bracket. #3. It is extremely important that the boater understands the significance of the transoms height. 7. Step 4. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. For most boaters this is a no brainer, but for the novice or inexperienced boater it may be a tougher question. Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? 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. It is where the outboard is mounted, and some boat owners place the name of the boat. storeDisplayName: "Marine Parts Warehouse", window.dataLayer = window.dataLayer || []; primeApr: 12.99, Always weigh the risks of making adjustments. 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}'); 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. No one wants to have issues with a new transom or boat repairs. My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. Simply start with the engine in idle, followed by, If you decide to make some custom adjustments we have the. Your email address will not be published. Triton. An outboard motor can drive just about any sort of boat with proper mounting. 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. 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. (updated One of the great things about an outboard motor is how versatile it is. 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. These are vertically aligned so the boater can make adjustments. Well, raising the outboard motor can be an easy task for you. The height of the boat transom dictates the size of the outboard motor. a Detwiler manual jackplate. Increased RPM and additional horsepower feed the need for speed. It does not store any personal data. Take the center measurement from the top to the bottom of the hull. He is a Doing this can have adverse effects. If your outboard motor height. This was the height of my 225 Yamaha on my TR21 The transom angle is the vertical incline of the transom and is measured in degrees. Higher mounting decisions should be left to the professionals. The cookie is used to store the user consent for the cookies in the category "Other. Or it can have an angle degree as high as 30. 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. As a yacht designer and boater, I prefer longer shafts. var h = d.getElementsByTagName("head"), maxMicroAmount: 0.0, 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. Boats with more engine power and weight require longer shaft outboards for better balance. This will ensure the best performance. Thats it. Wherever the outboard clamping bracket is, use this as the basis for measurement. Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. This cookie is set by GDPR Cookie Consent plugin. By clicking Accept, you consent to the use of ALL the cookies. All boats are different, and the motor manufacturers produce a variety of standard lengths. This would not be a good thing. Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. However, you will need an understanding of how the degrees will alter the boats usability. It also decreases the boats lift and increases the time it takes for the boat to reach plane. Because of the increased friction, cavitation reduces efficiency. Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. Pretty easy to figure out but like I said its crucial to pairing a motor with a boat. The form of a boats transom varies depending on the manufacturer and model. What matters is the actual measurement in the specifications, not the name. d.addEventListener("DOMContentLoaded", function (e) { You dont have to be a mathematician to determine the correct boat transom angle. Take your time and understand your boat and your entire transom. mpeSelector: ".pt-mpe", If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. If it measures between 17 and 22, youll want to go with a long shaft motor. Plus, a low transom cut is an invitation for the water to flood the boat. All you need to do is measure how much to rise. To achieve this, the motor itself has to be attached at the correct height. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? of the "bullet" on your lower unit. 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. Safely but briskly accelerate. 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. 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. 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. And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. They keep water out of your prop and increase water pressure in the system. Also, how do you determine the length of an outboard transom? This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. Actual shaft length is 21.5" on those. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. This allows the engine to idle without the flow of the exhaust being restricted. If you have a question or need additional information. s.setAttribute("src", script); You also might not be able to lift the outboard out of the water entirely for storage. This is measured by the propeller shaft being parallel to the vessels bottom. For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. Basically, there are three main ways to measure motor There is a simple test to see if your outboard motor is set at the best height. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. If you have a jackplate, you may have to get a bit creative in your :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ Repowering your boat is one of the most expensive upgrades you can make. This measurement is primarily designed for single motor propulsion. Take a long straight edge, (long carpenter's level or long At least if its too long you can raise the motor or "build up" your transom. Each one has a totally different effect on the boats performance. Some fishing boats can handle the motor being underwater. clearInterval(interval); If the propeller fails to ventilate, the motor is mounted to low. The height of the boat transom dictates the size of the outboard motor. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. We also use third-party cookies that help us analyze and understand how you use this website. This measurement was approximately 4". The flat part of the bracket that rests on the transom when mounted will give you the same point of reference as the transom does on the boat.

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