Theyre also useful if the back of your boat has a non-standard measurement. debugMode: false, The cookies is used to store the user consent for the cookies in the category "Necessary". 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. 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. bracket. Industry standards dictate that for short shaft engines the transom height should be 15. Another important measurement is the transom angle. If it measures 15" or with in a inch of that you will need a short shaft outboard. 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). A reversetransom that sits too high can impact the propellers of the motor and motor bracket. For example, you can have the Mercury outboard shaft length by model code. This is probably the worst case scenario out of the two. However, you will need an understanding of how the degrees will alter the boats usability. Over time, Boating Hub has grown into a resource for boating enthusiasts around world. Take your time and understand your boat and your entire transom. Always weigh the risks of making adjustments. This restriction includes most fishing boats and longer sailboats. motor brackets
x\[D~OUCO6[j](l%ay <8cylY{.L2s#]~U6A|Wj]-oo|mubqY6wbY_|!>Z8(RB:RHeTzOGO_=~t\ 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. It also decreases the boats lift and increases the time it takes for the boat to reach plane. You
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Before we get started lets see what a boat transom is and what it does. 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. This email address is being protected from spambots. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. "brackets". 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. of the "bullet" on your lower unit. This cookie is set by GDPR Cookie Consent plugin. By clicking Accept, you consent to the use of ALL the cookies. var h = d.getElementsByTagName("head"), His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. h[0].appendChild(s); Then adjust the motor in a higher hole with a flat head screwdriver. The mounting height of the outboard engine is the equivalent of the distance between the base of the motor and the top of the propeller. It was a 23-foot Crestliner Grand Cayman pontoon boat. Here we will guide you in how to get the right boat transom height. Higher mounting decisions should be left to the professionals. I live for the weekends when I can go out on the water and escape the stress of life on land. Some boats are equipped with transom-hung outboards while others have a bracket. Boats that use longer outboard shafts include: Read the measurement on the transoms bottom. The transom is the back of the boat where the motor is hung. a Detwiler manual jackplate. 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. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. 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. ), and place it on the bottom of the pad in the center. Your email address will not be published. You dont have to be a mathematician to determine the correct boat transomangle. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. These are vertically aligned so the boater can make adjustments. The transom is the "back wall" of your boat, the most rearward part of your hull. High powered boats usually only come in long and extra-long variants. For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. 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. displayMicroOffers: false, up to the bottom of the motor brackets, (as in #1). Picking the right shaft length for your outboard is an essential step in getting the best performance from your boat. An inch or two probably wont make a big difference, but any more than that will lead to trouble. Shaft lengths are available in increments of 5. 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). It is unsafe to have the engine block too close to the water on a low transom. It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. 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. What types of boat need an extra long shaft? In the second photo, we've measure down from the top of the Detwiler
Then open up the clamp bucket. I mean it is better to be safe than sorry, am I right? Step 2: Three Variables to Consider Doing this can have adverse effects. 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. See diagram below. Using your existing control box and gauges will save you quite a bit of money in the end. s.setAttribute("type", "text/javascript"); Two years ago, I bought a Boston Whaler to fish off the coast. And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. A: The short answer is Yes. (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. Owners of bass boats, RIBs, or offshore fishing boats need to get this right. Outboard shaft length plays a crucial role in the performance of your boat. While this is the case there is certain saltwater motors that are extra extra long at 30. What Kind of Fuel Does Your Marine Engine Need? of the motor off the transom
It varies between different motors and boats. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. straight edge from the center of the pad, but this time you're measuring
I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. Lubrication System Engine Oil Mixed Gasoline. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. 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. How high exactly do you have to raise the transom?-. and I'll explain it better, (or point you to someone that can help. Other boats that need short shafts are: A: If you have a small boat with a 18 to 21 inch aft transom, youll most likely need a long shaft outboard. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ 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. This measurement would be the inches of
They keep water out of your prop and increase water pressure in the system. Then test the boat and adjust the height, if necessary . The first order of business is to measure your boat for the ideal fit. not sure that it's still used. We also use third-party cookies that help us analyze and understand how you use this website. The pressure behind your hand dropped as you slid your hand back and forth through the water. It can also improve the experience of driving a faster boat. Among them will be first-timers or those who have recently purchased their boats. #2. relation to pad
The average transom angle is around 14 degrees. In the photo above, we've measured from the motor bracket to the top of
Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. 2 0 obj
So from there, I will try to help out by asking questions about your boat such as what type it is and the length. Chances are the boat was designed with a specific size of outboard in mind. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. The outboard comes with mounting holes and brackets. Should I take the raft onto the water and measure the exact distance from the top of the transom to the water line? It is where the outboard is mounted, and some boat owners place the name of the boat. Anything bigger than that your obviously going to need an extra long shaft. Whether you already own a boat or looking for your first watercraft we are here to service your needs. 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. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. 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. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. Cavitation is when the propeller is out of the water due to the boat forming a wake of "air bubbles" or "vapor cavities" around the prop. The current measurement is the ventilation plate is about 1 1/2" above the true keel line which is about 24" in front of the motor edge. The propellers will also have trouble reaching the water. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. The propellers will also have trouble reaching the water. 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}'); Gear case sits just below or at the hull depth due to the deep v. Before we get started lets see what a boat transom is and what it does. boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. var addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@' + 'vanssports' + '.' + 'com';document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML += ''+addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5+'<\/a>'; For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. These cookies will be stored in your browser only with your consent. If you have a jackplate, you may have to get a bit creative in your
To measure the transom height, measure from the center on for transom (rear of the boat). I would ask you to go back and measure the transom of your boat. The Effects of Standard, Lower and Higher Mounting. Take your time and understand your boat and your entire transom. As a yacht designer and boater, I prefer longer shafts. But opting out of some of these cookies may affect your browsing experience. Check out the full chart of the Mercury outboard model code and its features. It is extremely important that the boater understands the significance of the transom's height. This cookie is set by GDPR Cookie Consent plugin. Depending on the manufacturer, size names might change. This is a measurement that has been used for BassCats, I'm
Step 2 requires the propeller's radius (check the user manual and then the technical drawing). To break it down a bit more for you: Short shafts are 15-inches long. 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. boats.com is part of the Boats Group Network. 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. Any questions? So you should just measure the height of the boat's transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Actual shaft length is 21.5" on those. This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. It is very versatile as it generally . I believe 20 to 21 inches is the optimum length for a lengthy shaft. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. Many boat transoms are modified to use a different length of outboard by using a bracket. Engine Oil Type Genuine or Recommended 2str Engine Oil. Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. The height of the boat transom dictates the size of the outboard motor. 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. I hope this helps someone out in their search for a new or newer outboard this season. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. Knowing how this can affect the overall operation of the boat is a factor to be considered. Add the two measurements and you get 6 1/2". Outboards designed for saltwater applications usually have longer shafts. When trimming your motor, they provide you a greater bow response. How do you measure a transom on an outboard motor? 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. Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. Boaters who consider going with a higher mount can see increased speeds. 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. I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. This measurement is primarily designed for single motor propulsion. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. Other boats that need long shafts are. Make sure that you are measuring straight up, at a 90 degree angle to
Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. Transom Outboard Engine Position - YouTube 0:00 / 0:56 Transom Outboard Engine Position BOATING SCENE 763 subscribers 609 211K views 5 years ago www.boatingscene.com.au Sometimes when your. The lowest point will likely be directly under your drain plug if youve got one. s.setAttribute("href", "https://cdn.paytomorrow.com/css/pt-mpe.min.css"); 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. resting on the transom if you had the motor all the way down on the boat
On the downside, a higher mount can interfere with the boaters steering capabilities. Brackets are also handy for boats that do not have flat transoms, like canoe-stern sailboats or fan-tailed motor vessels. You need JavaScript enabled to view it. And the rule of thumb is that you should keep the cavitation plate level with the bottom or keel of the boat. Mounting the outboard motor in accordance with the industry standards is important. The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. For slower boats, its less critical to. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. The amount of degrees the transom leans back from vertical is known as the transom angle. Most of the time, adding a hydrofoil to an outboard improves performance. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. To sum up, there is a simple calculator of the shaft length for outboard motors: Outboard Shaft Length = Transom Height +/- Factors. The transom is the rear wall of the boat where the outboard engine is mounted in the middle. Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. You can use a longer shaft than recommended and your boat will work fine. <>
A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. You can find your Mercury outboard model code on an ID plate or sticker. 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. A yardstick will help you determine if your outboard engine is at the right height. 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 average transom angle is around 14 degrees. |. 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. To achieve this, the motor itself has to be attached at the correct height. The transom angle is the vertical incline of the transom and is measured in degrees. If it measures 15" or with in a inch of that you will need a short shaft outboard. Happy boating! You need JavaScript enabled to view it. As summer approaches there will be more boaters taking to the water. mpeInit(); PayTomorrow.mpeInit({ 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. There is a simple test to see if your outboard motor is set at the best height. 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. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Measure from the top of the transom to the bottom of the hull. Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. 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. 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. Beginning boaters should be aware of the boats measurements. (In the case of the faster
Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. The center is the point where your outboard motor is (ideally) located. This was the height of my 225 Yamaha on my TR21
Why wont Touch ID be under the screen in the iPhone 15 and iPhone 16? When the boattransom is too low, the motor could end up underwater. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. Like Westshore Marine & Leisure on Facebook! All things considered, sticking with the industry standard is best for the beginner. He is also a certified marine technician and the author of a popular text on writing local history. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. The mounting height of an outboard motor can impact the speed and handling characteristics of the boat. As you can see, the measurement is about 2 1/2". Simply start with the engine in idle, followed bytrimming the motor out by one-half to full trim. As with anything, there are exceptions to the rule. Analytical cookies are used to understand how visitors interact with the website. How the outboard will sit on the back of the boat depends on how the transom is designed. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. In lower mounting, the engine is set lower than the recommended standard. This cookie is set by GDPR Cookie Consent plugin. Having the cavitation plate a bit lower than the transom is preferable to having it too high. 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. Doing so, will put the propeller right below the boat. This is somewhat similar to #2, in that you are again measuring with a
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See When St. Peters Basketball Games Are Today! This alone can outweigh the negatives when deciding to adjust the mount upwards. All things considered, sticking with the industry standard is best for the beginner. You also might not be able to lift the outboard out of the water entirely for storage. If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. stream
But in many cases, its a little more complicated than that alone. If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. Well, raising the outboard motor can be an easy task for you. 3 0 obj
Workboats, sailboats, and displacement-hulled boats fall into this category. (function () { The height is approximately six inches higher than with a propeller. The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. The boat transom can be flat with zero degree angles. Because of the increased friction, cavitation reduces efficiency. 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. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; 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. Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. However, youll notice a little increase in drag and a decrease in top-end performance. (127 mm). You'll need a short shaft outboard if it's 15 or less than an inch shorter. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". Follow Westshore Marine & Leisure on Wordpress! Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. 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. 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. the aluminum plate on top of the transom), to the bottom of the motor
Then finally test your outboard, if the mount is perfect. MPW eBay Store - Thousands of New OEM Old Stock Parts! The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". function loadScript(script) { This, however, is not recommended for the beginning boater. What's the best height for my boat motor? gtag('js', new Date()); The correct shaft length for your boat depends on a few factors. This, however, is not recommended for the beginning boater. Beginning boaters should be aware of the boats measurements. Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) You may wonder how deep your prop should be in the water. How can you figure out what your transom angle is? function gtag(){dataLayer.push(arguments);} All boats are different, and the motor manufacturers produce a variety of standard lengths. Other factors to consider when determining the mounting height of an outboard are related to performance. 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". As mentioned above, the operation of the propeller relies on the transom height. 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. Copyright 2017 Dealer Spike All Rights Reserved. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches.