how to measure transom height for outboard motor

Having the cavitation plate a bit lower than the transom is preferable to having it too high. The vertical distance between the interior of the clamp and the cavitation plate is the shaft length specified by the outboard manufacturer. It also includes attaching the right engine. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. Check out the full chart of the Mercury outboard model code and its features. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. Most of the time, adding a hydrofoil to an outboard improves performance. The boat transom can be flat with zero degree angles. 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. ensure that your measurement is accurate. In lower mounting, the engine is set lower than the recommended standard. Many boat transoms are modified to use a different length of outboard by using a bracket. The motor is what powers the boat so the two go hand-in-hand. out the confusion. The average transom angle is around 14 degrees. 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. Lubrication System Engine Oil Mixed Gasoline. and I'll explain it better, (or point you to someone that can help. straight edge on the top of the transom to "extend" it out will be to the flat part; if you measure to the bottom of the brackets It also cuts into speed and fuel efficiency. displayPrimeOffers: true, So if you are measuring the outboard shaft length for the powerboat, planing boat, or any boat for which the speed is the priority, take the outboard shaft length 1 to 1.5 (depending on your boat types) shorter than standard would be better. 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. bracket forward with a straight edge to where you can then measure up Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. Save my name, email, and website in this browser for the next time I comment. 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. All things considered, sticking with the industry standard is best for the beginner. The boat transom can be flat with zero degree angles. Your email address will not be published. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. Gear case sits just below or at the hull depth due to the deep v. 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. to where the brackets were actually resting on the transom. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. Gear Oil Quantity 195ml(6.6 Fl.oz.) Here we will guide you in how to get the right boat transom height. 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. Most of the standard engined boats it takes shafts that are 15-30inches long. PayTomorrow.mpeInit({ A: The short answer is Yes. not sure that it's still used. The distance between the ends of a transom is measured in inches. Then adjust the motor in a higher hole with a flat head screwdriver. This could also affect your travelling capabilities on the boat trailer. The transom in a boat today is a place to hang your outboard motor. Necessary cookies are absolutely essential for the website to function properly. One of the great things about an outboard motor is how versatile it is. 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. You'll need a short shaft outboard if it's 15 or less than an inch shorter. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. You need JavaScript enabled to view it. endobj The outboard shaft length is the vertical distance between the top of the mounting clamp bracket and the bottom of the cavitation plate (aka the ventilation plate). Each one has a totally different effect on the boats performance. If you have a question or need additional information,contact ustoday. h[0].appendChild(s); h[0].appendChild(s); When you measure the width of the stern, mark the center with a grease pencil. What Kind of Fuel Does Your Marine Engine Need? Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. 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. gtag('config', 'G-QX0Y76NH40'); Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. An outboard motor can drive just about any sort of boat with proper mounting. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. storeDisplayName: "Marine Parts Warehouse", The how to measure the shaft length of an outboard motor is a question that many people have asked. Using your existing control box and gauges will save you quite a bit of money in the end. 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). The outboard comes with mounting holes and brackets. Will Charpentier is a writer who specializes in boating and maritime subjects. Here we will guide you in how to get the right boat transom height. See When St. Peters Basketball Games Are Today! But in many cases, its a little more complicated than that alone. Always weigh the risks of making adjustments. The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. The brackets can add 1 inch to the overall mounting height of the outboard. You s.setAttribute("type", "text/javascript"); 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. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Well, raising the outboard motor can be an easy task for you. This will be the How can you figure out what your transom angle is? If it measures between 17 and 22, you'll want to go with a long shaft motor. Beefier jack plates can be fitted should a boater be looking to mount an outboard with a shorter shaft than their transom demands. 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. brackets. To achieve this, the motor itself has to be attached at the correct height. Beginning boaters should be aware of the boats measurements. Is my outboard long or short shaft? 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). Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. You reply, "Im not sure, I think its a long". Repowering your boat is one of the most expensive upgrades you can make. This distance is very important to the performance of you boat. Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. This, however, is not recommended for the beginning boater. Of course, its always best to go with standard practices when choosing thebest boat engine. 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. Use the mounting bracket on the motor to know where it will sit on the boat. Before we get started lets see what a boat transom is and what it does. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". Again, make sure that you are measuring to the flat part of the brackets; 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. This is a measurement that has been used for BassCats, I'm }) } }); })(document); parallel with the straight edge. 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. As a dealer I run into this situation from time to time, which is fine but getting the right length outboard for your boat is crucial. } Because of the increased friction, cavitation reduces efficiency. If you go too short your more than likely going to cavitate and loose power. I mean it is better to be safe than sorry, am I right? I show you how to consistently measure your prop to pad height. But opting out of some of these cookies may affect your browsing experience. The first step is to determine the height of your boat's transom. 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. Shaft lengths are available in increments of 5. Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. if (PayTomorrow) { Make sure that you are measuring straight up, at a 90 degree angle to Next, measure from your centerline to where the outboard will be mounted on each side. The cookie is used to store the user consent for the cookies in the category "Other. function mpeInit() { We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. You also might not be able to lift the outboard out of the water entirely for storage. The transom is the back of the boat where the motor is hung. What is Transom Height? And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. What Types of Documents Can be Sent to your Kindle Library? Boats that use longer outboard shafts include: Theyre also useful if the back of your boat has a non-standard measurement. var h = d.getElementsByTagName("head"), Expectedly, when the transom angle is zero, it means it is flat. Boats with more engine power and weight require longer shaft outboards for better balance. But, how do you measure it? s = d.createElement("script"); 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. There up to the bottom of the motor brackets, (as in #1). If you decide to make some custom adjustments we have theexperience and know-howto make it happen. Brackets are also handy for boats that do not have flat transoms, like canoe-stern sailboats or fan-tailed motor vessels. Its still smart to measure it yourself though, just in case, the design changed over the years. It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. Long shafts are 20-inches long. The cookie is used to store the user consent for the cookies in the category "Performance". The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. Ten years ago I bought my first boat. The faster your boat, the more critical it is to get the sizing just right. MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. 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. The general guideline for longer shaft outboards is that the transom height should be at least 20 inches (50,8cm) above the waterline. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. I believe 20 to 21 inches is the optimum length for a lengthy shaft. Outboard Motor Shaft Length: How do I measure? This is also known as the shaft length. 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. On this type of boat, if you are in doubt, default to the longer-shafted outboard. See diagram below. endobj It is where the outboard is mounted, and some boat owners place the name of the boat. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. 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. var xmlHttp = new XMLHttpRequest(); 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. It does not store any personal data. How to Buy a Boat: Tips for a First Time Buyer, Top 10 New Fishing Boats for Under $20,000, What Type is Right for You? I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. Knowing how this can affect the overall operation of the boat is a factor to be considered. bassboat can be a bit confusing at times; hopefully this will help sort Engine Oil Type Genuine or Recommended 2str Engine Oil. Figuring out how to measure motor height on a You must be still in the blue about that matter. This alone can outweigh the negatives when deciding to adjust the mount upwards. Depending on the manufacturer, size names might change. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. #1: Height Beginning boaters should be aware of the boats measurements. 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. Check out some hot FAQs to help you get the proper outboard shaft lengths. As with anything, there are exceptions to the rule. (In the case of the faster Cavitation plates are used on the bottom components of boats to help them operate better. Analytical cookies are used to understand how visitors interact with the 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. Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? since 1986. It varies between different motors and boats. Required fields are marked *. This alone can outweigh the negatives when deciding to adjust the mount upwards. This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). However, you will need an understanding of how the degrees will alter the boats usability. Another important measurement is the transom angle. Take your time and understand your boat and your entire transom. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. publicId: "32bf3437d1346295e03ebcf545f9c839", Check out the Westshore Marine & Leisure google plus page! 5/rC,aQhsK@Q. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. How the outboard will sit on the back of the boat depends on how the transom is designed. Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. <> There are a series of four to six holes at the top of the bracket, and the lower bolts actually fit into slots. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. Chances are the boat was designed with a specific size of outboard in mind. Higher mounting decisions should be left to the professionals. These cookies track visitors across websites and collect information to provide customized ads. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. Some fishing boats can handle the motor being underwater. 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. What the relationship to the pontoons is, I couldn't say. What types of boat need an extra long shaft? Extra-long shafts are 25-inches long. Doing so, will put the propeller right below the boat. Doing this can have adverse effects. How Transom Height Is Measured To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. There is a simple test to see if your outboard motor is set at the best height. Most transom savers can support up to a 150HP motor, which is sufficient for most regular boats. disregard the "hooks" at the front of the In lower mounting, the engine is set lower than the recommended standard. The propellers will also have trouble reaching the water. This, however, is not recommended for the beginning boater. Typical motor lengths include the following. Or it can have an angle degree as high as 30. This will ensure the best performance. If you are running a twin-engine setup, then measure the same distance from each clamping plate to the bottom of the hull. This measurement would be the inches of 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. The height of the boat transom dictates the size of the outboard motor. Place the bracket on the transom to the left of the main outboard or rudder. Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. 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. The average transom angle is around 14 degrees. For over five years he has worked as a newspaper reporter and historic researcher. debugMode: false, This is somewhat similar to #2, in that you are again measuring with a (function () { the aluminum plate on top of the transom), to the bottom of the motor There are instances where a lower mount may be okay. The point where these measurements intersect is your centerline. It will ensure that the outboards trim will be effective, and it will save you gas too. It is very versatile as it generally . It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. 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. As you can see, the measurement is about 2 1/2". As a yacht designer and boater, I prefer longer shafts. It also decreases the boats lift and increases the time it takes for the boat to reach plane. measuring; you may have to "extend" the flat part of the Youll need a short shaft outboard if its 15 or less than an inch shorter. High powered boats usually only come in long and extra-long variants. var addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@' + 'vanssports' + '.' + 'com';document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML += ''+addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5+'<\/a>'; 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. boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. Remanufactured 4 Cylinder 4-Stroke Cylinder Heads, Remanufactured 6 Cylinder 4-Stroke Cylinder Heads, Trim Relays, Trim Solenoids & Sending Units, Remanufactured V6 & V8 4-Stroke Cylinder Heads, Volvo Cobra SX Bearings and Bearing Carriers, Volvo Cobra SX Driveshaft, U-Joints & Parts, Volvo Cobra SX Transom Assembly & Bellows. The pros and cons of properly . Copyright 2017 Dealer Spike All Rights Reserved. If your outboard motor height. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! boats.com is part of the Boats Group Network. By clicking Accept, you consent to the use of ALL the cookies. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. What matters is the actual measurement in the specifications, not the name. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. It is unsafe to have the engine block too close to the water on a low transom. var prefix = 'ma' + 'il' + 'to'; gtag('js', new Date()); The transom is the rear wall of the boat where the outboard engine is mounted in the middle. Doing this can have adverse effects. As mentioned above, the operation of the propeller relies on the transom height. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. Check out the Westshore Marine & Leisure Youtube page! A deep Vee hull will result in a different measurement than a flatter . your motor will be higher.) Place the point of a yardstick at the middle of the top of the boat transom. Like Westshore Marine & Leisure on Facebook! Over time, Boating Hub has grown into a resource for boating enthusiasts around world. You may wonder how deep your prop should be in the water. How high exactly do you have to raise the transom?-. With the long side (22 1/2), place a carpenters square ) in opposition to the keel. Boaters who consider going with a higher mount can see increased speeds. These two measurements will give you the length of the shaft you need. To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). 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). 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. He is a steel ruler, etc. Pad to bottom of You run the risk of possibly unsafe handling if you attempt to put a long shaft engine on a transom designed for a short shaft engine. 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. Simply start with the engine in idle, followed bytrimming the motor out by one-half to full trim. However, your boat will have slightly more drag which will reduce your maximum speed. It was a 23-foot Crestliner Grand Cayman pontoon boat. Look at the part of your motor that would be You can use a longer shaft than recommended and your boat will work fine. On the downside, a higher mount can interfere with the boaters steering capabilities. Or measure from the main engine prop up to the water line? e-mail If you decide to make adjustments, please consult a marine engine dealer about the boat design. Propshaft in His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. would be more accurate.) A transom saver, which can change the spacing between the lower unit and the trailer, negates some of the support. C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? The correct shaft length for your boat depends on a few factors. An inch or two probably wont make a big difference, but any more than that will lead to trouble. 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? At least if its too long you can raise the motor or "build up" your transom. 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. To measure the transom height, measure from the center on for transom (rear of the boat). 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.

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