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Having the cavitation plate a bit lower than the transom is preferable to having it too high. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. The transom is the back of the boat where the motor is hung. As a result, the issue is whether my boat need a short shaft or long shaft motor. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. s = d.createElement("link"); motor brackets This website uses cookies to improve your experience while you navigate through the website. If you have already measured you transom tip to bottom to be 20", then if you place aux sdieways to central engine your available transom height will be probably 1"-1.5" " higher and work perfecty. 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. The average transom angle is around 14 degrees. Then test the boat and adjust the height, if necessary . I hope this helps someone out in their search for a new or newer outboard this season. The center is the point where your outboard motor is (ideally) located. 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. 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. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). In the case of a dinghy or johnboat, this point may be the top of the transom. Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. So from there, I will try to help out by asking questions about your boat such as what type it is and the length. These cookies track visitors across websites and collect information to provide customized ads. 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. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. stream Follow Westshore Marine & Leisure on Wordpress! How can you figure out what your transom angle is? When you measure the width of the stern, mark the center with a grease pencil. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. Typical motor lengths include the following. How high exactly do you have to raise the transom?-. This is probably the worst case scenario out of the two. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. up to the bottom of the motor brackets, (as in #1). So you should just measure the height of the boats transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. Measure from the top of the straight edge to the center of the front If so, send me an When fighting waves from the stern, a 20-inch transom is considerably safer. The motor is what powers the boat so the two go hand-in-hand. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. It is extremely important that the boater understands the significance of the transom's height. Get the latest updates on new products and upcoming sales, 2023 Marine Parts Warehouse Incorporated Increased RPM and additional horsepower feed the need for speed. These cookies ensure basic functionalities and security features of the website, anonymously. This restriction includes most fishing boats and longer sailboats. One of the factors in determining the height of the outboard is the placement of the exhaust port on the lower unit of the outboard engine. Take a long straight edge, (long carpenter's level or long This, however, is not recommended for the beginning boater. If you have a jackplate, you may have to get a bit creative in your Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. The faster your boat, the more critical it is to get the sizing just right. Where Onboard a Boat is the Transom Located and More About Transom Heights A propeller operates based on the height of the transom. Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. Most of the time, adding a hydrofoil to an outboard improves performance. Mounting the motor lower on the boat transom can create excessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. maxTerm: 36, This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. This measurement would be the inches of Allowing the propeller to pull water from underneath and push it out behind the boat. All boats are different, and the motor manufacturers produce a variety of standard lengths. |. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. I show you how to consistently measure your prop to pad height. This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). 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. Extra-long shafts are 25-inches long. One of the great things about an outboard motor is how versatile it is. Outboard shaft length plays a crucial role in the performance of your boat. You can order an outboard in lengths ranging from 15 inches to 30 inches, depending on its power output and possible uses. Here we look at the effects of standard, lower and higher mounting. The transom in a boat today is a place to hang your outboard motor. Anything bigger than that your obviously going to need an extra long shaft. steel ruler, etc. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ endobj 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. Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. *The Factors indicates the adjustment affected by on your boat type, the outboard working environment, and the transom distance as discussed above. Picking the right shaft length for your outboard is an essential step in getting the best performance from your boat. What Types of Documents Can be Sent to your Kindle Library? Save my name, email, and website in this browser for the next time I comment. I also love helping others, which is why I created this website. 2019s List of the Best Recreational Pontoon Boats for Sale. 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. #2. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". The cookie is used to store the user consent for the cookies in the category "Other. With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. In extremes, the engine can have overheating problems if the boat is raised to a point where the water inlets for the cooling system are out of the water. Save my name, email, and website in this browser for the next time I comment. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. The boat transom can be flat with zero degree angles. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. A transom saver, which can change the spacing between the lower unit and the trailer, negates some of the support. Add the two measurements and you get 6 1/2". Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. Two years ago, I bought a Boston Whaler to fish off the coast. 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 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. Outboard Motor Shaft Length: How do I measure? measuring; you may have to "extend" the flat part of the Each one has a totally different effect on the boats performance. This cookie is set by GDPR Cookie Consent plugin. If you decide to make some custom adjustments we have theexperience and know-howto make it happen. publicId: "32bf3437d1346295e03ebcf545f9c839", Lubrication System Engine Oil Mixed Gasoline. MPW eBay Store - Thousands of New OEM Old Stock Parts! The transom is the "back wall" of your boat, the most rearward part of your hull. Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. 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. You must be still in the blue about that matter. 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). Workboats, sailboats, and displacement-hulled boats fall into this category. What the relationship to the pontoons is, I couldn't say. Boats with more engine power and weight require longer shaft outboards for better balance. }) } }); })(document); boats.com is part of the Boats Group Network. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. s.setAttribute("src", script); As mentioned above, the operation of the propeller relies on the transom height. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. We also use third-party cookies that help us analyze and understand how you use this website. 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. On the downside, a higher mount can interfere with the boaters steering capabilities. var h = d.getElementsByTagName("head"), For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. If you have a question or need additional information. But in many cases, its a little more complicated than that alone. 2 0 obj var interval = setInterval(function () { Any questions? I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. #3. Happy boating! 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. A big NO. 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 estimated by using the center line to measure from the bottom of the hull to the top of the transom. A yardstick will help you determine if your outboard engine is at the right height. Then adjust the motor in a higher hole with a flat head screwdriver. The dealer just hit you with the long or short shaft question and you have no clue as to what you need or even what he's talking about. 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. However, you will need an understanding of how the degrees will alter the boats usability. A reversetransom that sits too high can impact the propellers of the motor and motor bracket. Some may call it a standard length while others may call it a short or a long shaft. What types of boat need an extra long shaft? The height is approximately six inches higher than with a propeller. var h = d.getElementsByTagName("head"), However, there may be times when a boater strays away from these recommendations. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. 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. 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. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. This measurement was approximately 4". Outboards designed for saltwater applications usually have longer shafts. bassboat can be a bit confusing at times; hopefully this will help sort d.addEventListener("DOMContentLoaded", function (e) { Then, you can pick the right engine. 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. You reply, "Im not sure, I think its a long". Read the following to get the optimal shaft length for outboard motors! Add yours in the comment and Ill get back to you asap. actually have the propshaft above the pad.). The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. No one wants to have issues with a new transom or boat repairs. height (that I'm aware of); probably the most common is: Analytical cookies are used to understand how visitors interact with the website. There are also specialty motor shaft lengths. Or it can have an angle degree as high as 30. 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. of the motor off the transom What is the Virtual Sundance Film Festival? Check out the full chart of the Mercury outboard model code and its features. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. }, 100); <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Industry standards dictate that for short shaft engines the transom height should be 15. Should I take the raft onto the water and measure the exact distance from the top of the transom to the water line? My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. Since the length of the shaft of your outboard is associated with the size boat, smaller engines will generally have shorter shafts. } This alone can outweigh the negatives when deciding to adjust the mount upwards. There are a series of four to six holes at the top of the bracket, and the lower bolts actually fit into slots. Not to measure boat speed, but to gauge the mounting height of the outboard motor on the boat transom. As with anything, there are exceptions to the rule. These two measurements will give you the length of the shaft you need. mpeSelector: ".pt-mpe", It is where the outboard is mounted, and some boat owners place the name of the boat. Other boats that need extra long shafts are: Read my other articles on outboard motors. These cookies will be stored in your browser only with your consent. 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.