A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. 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. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. This is simply a measurement taken from the top of the transom (top of If your outboard motor height. Outboards designed for saltwater applications usually have longer shafts. These are vertically aligned so the boater can make adjustments. When the boat transom is too low, the motor could end up underwater. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. The amount of degrees the transom leans back from vertical is known as the transom angle. I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. What the relationship to the pontoons is, I couldn't say. Its important to note that manufacturers call their models different things. Among them will be first-timers or those who have recently purchased their boats. August 9/08). Small portable outboards ranging from 2 to 20 horsepower are usually sold only in short or long shaft versions. What matters is the actual measurement in the specifications, not the name. Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. These two measurements will give you the length of the shaft you need. Triton. The standard installation of an outboard has the top of the transom of the boat at the same level as the bottom of the motor portion of the outboard. The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. The Effects of Standard, Lower and Higher Mounting. Measure straight down to the lowest point on the hull. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. 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. How the outboard will sit on the back of the boat depends on how the transom is designed. Again, make sure that you are measuring to the flat part of the brackets; The lowest point will likely be directly under your drain plug if youve got one. These cookies will be stored in your browser only with your consent. If you said something smaller than that, thats where it can get tricky. Analytical cookies are used to understand how visitors interact with the website. Simply start with the engine in idle, followed by, If you decide to make some custom adjustments we have the. 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. from the transom. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. A: The answer varies by boat, but here are some rules of thumb for matching a short shaft outboard to your boat. If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. Your email address will not be published. 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. On the downside, a higher mount can interfere with the boaters steering capabilities. a Detwiler manual jackplate. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. 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. If the propeller fails to ventilate, the motor is mounted to low. 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. gtag('js', new Date()); Step 4. If it measures 15" or with in a inch of that you will need a short shaft outboard. The transom is the flat vertical section at the rear of the boat. A reversetransom that sits too high can impact the propellers of the motor and motor bracket. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; It can also improve the experience of driving a faster boat. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. Wherever the outboard clamping bracket is, use this as the basis for measurement. The transom is the flat vertical section at the rear of the boat. How Transom Height Is Measured You will also risk hitting bottom or submerge objects more frequently such as rocks or logs. Since the ventilation plate & foil are burried under water it is obviously too low. Actual shaft length is 21.5" on those. Make sure that you are measuring straight up, at a 90 degree angle to The point where these measurements intersect is your centerline. With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. 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. It does not store any personal data. Safely but briskly accelerate. It is extremely important that the boater understands the significance of the transoms height. Take the center measurement from the top to the bottom of the hull. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. 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. This, however, is not recommended for the beginning boater. It is extremely important that the boater understands the significance of the transoms height. The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. Measure from the top of the straight edge to the center of the front If you decide to make adjustments, please consult a marine engine dealer about the boat design. 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. This is handy if youre shopping for second-hand outboards or looking to sell the one that came with your boat. The pros and cons of properly . #3. To sum up, there is a simple calculator of the shaft length for outboard motors: Outboard Shaft Length = Transom Height +/- Factors. 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. priceSelector: ".price--withoutTax, span.price.price--withTax", When trimming your motor, they provide you a greater bow response. You need JavaScript enabled to view it. 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. When it gets to the short side (14), When the inner corner of the square comes into touch with the transom, measure the distance between the inside corner of the square and the boat bottom (see drawing below). (616) 364-0666, On all contiguous US part orders over $100. Extra-long shafts are 25-inches long. The brackets can add 1 inch to the overall mounting height of the outboard. As mentioned above, the operation of the propeller relies on the transom height. Most of the time, adding a hydrofoil to an outboard improves performance. The general guideline for longer shaft outboards is that the transom height should be at least 20 inches (50,8cm) above the waterline. |. They keep water out of your prop and increase water pressure in the system. Measure the area of the transom directly where the engine will be mounted. the aluminum plate on top of the transom), to the bottom of the motor Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. You can find your Mercury outboard model code on an ID plate or sticker. You reply, "Im not sure, I think its a long". }) } }); })(document); Having the cavitation plate a bit lower than the transom is preferable to having it too 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. and I'll explain it better, (or point you to someone that can help. The motor is what powers the boat so the two go hand-in-hand. debugMode: false, Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. resting on the transom if you had the motor all the way down on the boat The rearmost structural member of your boat, it not only distributes the stress of the hull generated by the bow's impact as it cleaves the water, it's the place you hang your outboard motor. I mean it is better to be safe than sorry, am I right? If you have a question or need additional information,contact ustoday. 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. Required fields are marked *. 3 0 obj If you decide to make some custom adjustments we have theexperience and know-howto make it happen. bassboat can be a bit confusing at times; hopefully this will help sort You also have the option to opt-out of these cookies. 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. Whether you already own a boat or looking for your first watercraft we are here to service your needs. It varies between different motors and boats. 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. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. The cookie is used to store the user consent for the cookies in the category "Analytics". This measurement would be the inches of This alone can outweigh the negatives when deciding to adjust the mount upwards. 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. var xmlHttp = new XMLHttpRequest(); A: The short answer is Yes. The propellers will also have trouble reaching the water. var addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@' + 'vanssports' + '.' + 'com';document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML += ''+addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5+'<\/a>'; Because of the increased friction, cavitation reduces efficiency. What is Transom Height? Buying a boat can be an exciting purchase. If it measures 15" or with in a inch of that you will need a short shaft outboard. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. 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. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. However, the motor should not be raised more than 5 inches above the standard position. jackplate to a point level with the top of the transom. Where Onboard a Boat is the Transom Located and More About Transom Heights A propeller operates based on the height of the transom. } Allowing the propeller to pull water from underneath and push it out behind the boat. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. If the propeller fails to ventilate, the motor is mounted to low. The center is the point where your outboard motor is (ideally) located. 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. To measure the transom height, measure from the center on for transom (rear of the boat). This cookie is set by GDPR Cookie Consent plugin. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. 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. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. primeApr: 12.99, Next, measure from your centerline to where the outboard will be mounted on each side. As you can see, the measurement is about 2 1/2". Its where the outboard motor is attached, and its also where some boat owners put the boats name. The height of the boat transom dictates the size of the outboard motor. 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. Some outboards have a serial number that tells you which shaft length to go for. 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. In the case of a dinghy or johnboat, this point may be the top of the transom. %PDF-1.7 As mentioned above, the operation of the propeller relies on the transom height. In the second photo, we've measure down from the top of the Detwiler want to measure from the transom to the flat part of this bracket, This email address is being protected from spambots. But, how do you measure it? It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. function mpeInit() { (updated Over time, Boating Hub has grown into a resource for boating enthusiasts around world. Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. A2: Instead of changing to the short outboard shaft, you can try the Jack Plate first. The transom is the rear wall of the boat where the outboard engine is mounted in the middle. However, your boat will have slightly more drag which will reduce your maximum speed. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. })(); The transom is the "back wall" of your boat, the most rearward part of your hull. This would not be a good thing. This could also affect your travelling capabilities on the boat trailer. Always weigh the risks of making adjustments. steel ruler, etc. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Youll need a short shaft outboard if its 15 or less than an inch shorter. out the confusion. The greater the number, the more the drive may sway (also called tuck under or negative trim). If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. Add the two measurements and you get 6 1/2". xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); If you have a jackplate, you may have to get a bit creative in your Buying a boat can be an exciting purchase. A deep Vee hull will result in a different measurement than a flatter . It is extremely important that the boater understands the significance of the transom's height. 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. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. All things considered, sticking with the industry standard is best for the beginner. Many boat transoms are modified to use a different length of outboard by using a bracket. For slower boats, its less critical to. 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. Here we will guide you in how to get the right boat transom height. The transom angle is the vertical incline of the transom and is measured in degrees. Many single-engine boats mount a smaller auxiliary motor for emergency use. If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. 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. To measure your outboard motor shaft length, measure from the bottom of the mounting bracket where it rests on the transom to the top of the cavitation plate, this is the horizontal surface of the lower unit immediately above the propeller. There is a simple test to see if your outboard motor is set at the best height. displayPrimeOffers: true, You dont have to be a mathematician to determine the correct boat transomangle. Then open up the clamp bucket. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! manufacturer will recommend the outboard height according to the bracket shape and length. This will be the It is very versatile as it generally . This distance is very important to the performance of you boat. 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). So how to determine the outboard shaft length? Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. of the motor off the transom If it measures between 17 and 22, you'll want to go with a long shaft motor. 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. Cavitation plates are used on the bottom components of boats to help them operate better. would be more accurate.) It also cuts into speed and fuel efficiency. 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. The cookie is used to store the user consent for the cookies in the category "Other. Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. Any questions? This measurement is primarily designed for single motor propulsion. What Kind of Fuel Does Your Marine Engine Need? % var prefix = 'ma' + 'il' + 'to'; Check out the Westshore Marine & Leisure google plus page! The motor is what powers the boat so the two go hand-in-hand. Using your existing control box and gauges will save you quite a bit of money in the end. As with anything, there are exceptions to the rule. Whether you already own a boat or looking for your first watercraft we are here to service your needs. relation to pad Or measure from the main engine prop up to the water line? 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. Mounting the outboard motor in accordance with the industry standards is important. mpeInit(); As with anything, there are exceptions to the rule. 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. Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. 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". Some may call it a standard length while others may call it a short or a long shaft. 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. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. xmlHttp.setRequestHeader('Content-Type', 'application/json'); It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. Your email address will not be published. These are vertically aligned so the boater can make adjustments. loadScript(ptScript); C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. boats.com is part of the Boats Group Network. Each one has a totally different effect on the boats performance. Then adjust the motor in a higher hole with a flat head screwdriver. The how to measure the shaft length of an outboard motor is a question that many people have asked. When you measure the width of the stern, mark the center with a grease pencil. h[0].appendChild(s); Extra-extra long shafts are 30-inches long. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. since 1986. It is unsafe to have the engine block too close to the water on a low transom. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. Save my name, email, and website in this browser for the next time I comment. Ideally, you want the outboards cavitation plate, also called the anti-ventilation plate, to be at the same level as the bottom of your hull. if (PayTomorrow) { Look at the part of your motor that would be The height of the boat transom dictates the size of the outboard motor. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. But in many cases, its a little more complicated than that alone. The pressure behind your hand dropped as you slid your hand back and forth through the water.