how to measure transom height for outboard motor

Before we get started lets see what a boat transom is and what it does. h[0].appendChild(s); This would not be a good thing. 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. 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. Basically, there are three main ways to measure motor endobj It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. The boat transom can be flat with zero degree angles. What the relationship to the pontoons is, I couldn't say. Yes, if there is adequate space while the engine is tilted in the up position, a larger shaft length than what is specified may be used. Workboats, sailboats, and displacement-hulled boats fall into this category. No one wants to have issues with a new transom or boat repairs. 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 you can see, the measurement is about 2 1/2". If it measures 15" or with in a inch of that you will need a short shaft outboard. So in hopes that this will help out some new boaters this spring, here's a little rundown on outboard shaft sizes and how to figure out which one you actually need. The point where these measurements intersect is your centerline. What matters is the actual measurement in the specifications, not the name. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. On the downside, a higher mount can interfere with the boaters steering capabilities. 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. 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. clearInterval(interval); Well, raising the outboard motor can be an easy task for you. I believe 20 to 21 inches is the optimum length for a lengthy shaft. Your email address will not be published. Measure straight down to the lowest point on the hull. displayPrimeOffers: true, xmlHttp.setRequestHeader('Content-Type', 'application/json'); As summer approaches there will be more boaters taking to the water. The transom in a boat today is a place to hang your outboard motor. 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. 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. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) If it measures 15" or with in a inch of that you will need a short shaft outboard. Installing a Kicker Motor Bracket - Gone Outdoors trimming the motor out by one-half to full trim. Some boats are equipped with transom-hung outboards while others have a bracket. Place the bracket on the transom to the left of the main outboard or rudder. If it measures between 17 and 22, you'll want to go with a long shaft motor. An outboard motor can drive just about any sort of boat with proper mounting. }) } }); })(document); Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. But opting out of some of these cookies may affect your browsing experience. It is unsafe to have the engine block too close to the water on a low transom. 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. These are vertically aligned so the boater can make adjustments. Higher mounting decisions should be left to the professionals. 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. Measure from the top of the transom to the bottom of the hull. This is measured by the propeller shaft being parallel to the vessels bottom. So how to determine the outboard shaft length? 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. Doing this can have adverse effects. out the confusion. When trimming your motor, they provide you a greater bow response. #3. 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. Guide to Boat Transom Heights - Marine Parts Warehouse Allowing the propeller to pull water from underneath and push it out behind the boat. The amount of degrees the transom leans back from vertical is known as the transom angle. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. When the boat transom is too low, the motor could end up underwater. 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. Happy boating! The propellers will also have trouble reaching the water. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. 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. If you went too long it would still work but it may lack in performance. Be sure to measure carefully and research thoroughly before diving in. Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. The center is the point where your outboard motor is (ideally) located. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. I live for the weekends when I can go out on the water and escape the stress of life on land. The height of the boat transom dictates the size of the outboard motor. 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. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). However, your boat will have slightly more drag which will reduce your maximum speed. Also, how do you determine the length of an outboard transom? These cookies track visitors across websites and collect information to provide customized ads. #1: Height If you have a question or need additional information. Motor height on pontoon? | Boating Forum - iboats Boating Forums displayMicroOffers: false, How to Measure a Boat Transom - Gone Outdoors If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. 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. Boats that use longer outboard shafts include: At least if its too long you can raise the motor or "build up" your transom. If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. (Any measurement given as "off the transom" What's the best height for my boat motor? Outboards designed for saltwater applications usually have longer shafts. To sum up, there is a simple calculator of the shaft length for outboard motors: Outboard Shaft Length = Transom Height +/- Factors. 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. of the "bullet" on your lower unit. No one wants to have issues with a new transom or boat repairs. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Required fields are marked *. A deep Vee hull will result in a different measurement than a flatter . However, there may be times when a boater strays away from these recommendations. If possible for your peace of mind and not let down that magnificent purchase opportunity, place that 08 kicker at back transom and test for yourself. Setting Height of Outboard Motor - YouTube 0:00 / 0:46 Setting Height of Outboard Motor nates90 71 subscribers Subscribe 83 Share 63K views 7 years ago #boatservice #outboardmotor. Take the center measurement from the top to the bottom of the hull. Or measure from the main engine prop up to the water line? It is where the outboard is mounted, and some boat owners place the name of the boat. (Putting a This distance is very important to the performance of you boat. Thats it. The shaft length for outboard motors has nothing to do with the water line. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. var prefix = 'ma' + 'il' + 'to'; When measuring the transom height, you should start from the hull's bottom at the boat's center line up to the top of the transom. By clicking Accept, you consent to the use of ALL the cookies. Industry standards dictate that for short shaft engines the transom height should be 15. 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. Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. You may wonder how deep your prop should be in the water. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. Read the following to get the optimal shaft length for outboard motors! ), and place it on the bottom of the pad in the center. If the propeller fails to ventilate, the motor is mounted to low. Extra-extra long shafts are 30-inches long. PDF Outboard shaft lengths and transoms - Boat Builder Central 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}'); This is probably the worst case scenario out of the two. Transom Outboard Engine Position - YouTube 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. It also cuts into speed and fuel efficiency. Mounting the outboard motor in accordance with the industry standards is important. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. 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. Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. On the downside, a higher mount can interfere with the boaters steering capabilities. A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. 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. 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. My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. With this in mind, how can I determine if my outboard has a short or long shaft? All things considered, sticking with the industry standard is best for the beginner. Copyright 1999-2023 Boats Group. There Among them will be first-timers or those who have recently purchased their boats. The first step is to determine the height of your boat's transom. Measuring Motor Height - BassBoat Central This measurement would be the inches of (function () { Safely but briskly accelerate. Then open up the clamp bucket. maxAmount: 6500.0, Many boat transoms are modified to use a different length of outboard by using a bracket. Cavitation plates are used on the bottom components of boats to help them operate better. This is also known as the shaft length. The boat transom can be flat with zero degree angles. loadScript(ptScript); Having the cavitation plate a bit lower than the transom is preferable to having it too high. 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. Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" "brackets". What Is a Transom? Where Onboard a Boat is It Located? 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. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Safely but briskly accelerate. How To Mount An Outboard Motor Properly - Start to Finish! Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. PayTomorrow.mpeInit({ How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. 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. Spark Plug 25.0nm(18.4 Ft-lb) (2.55 Kgf-m) If you decide to make some custom adjustments we have theexperience and know-howto make it happen. Using your existing control box and gauges will save you quite a bit of money in the end. How do you measure a transom on an outboard motor? These two measurements will give you the length of the shaft you need. But, how do you measure it? priceSelector: ".price--withoutTax, span.price.price--withTax", xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); Mounting kicker motor - General Discussion Forum | In-Depth Outdoors Follow Westshore Marine & Leisure on Twitter! Pad to bottom of Theyre also useful if the back of your boat has a non-standard measurement. Always weigh the risks of making adjustments. An inch or two probably wont make a big difference, but any more than that will lead to trouble. maxTerm: 36, endobj With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. Check out the full chart of the Mercury outboard model code and its features. parallel with the straight edge. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. As mentioned above, the operation of the propeller relies on the transom height. (3) Move horizontally across the chart until you hit the graph curve. 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). 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 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. 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. Propshaft in 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. 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. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. If the height of the boat transom is off it can cause major issues. var path = 'hr' + 'ef' + '='; 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. Boats with more engine power and weight require longer shaft outboards for better balance. Each one has a totally different effect on the boats performance. There is a simple test to see if your outboard motor is set at the best height. bracket forward with a straight edge to where you can then measure up boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. However, the motor should not be raised more than 5 inches above the standard position. 5/rC,aQhsK@Q. Later in the article is an image that shows you exactly where to measure. The motor is what powers the boat so the two go hand-in-hand. Plus, a low transom cut is an invitation for the water to flood the boat. Chances are the boat was designed with a specific size of outboard in mind. Proper Mounting Height for an Outboard - Gone Outdoors I show you how to consistently measure your prop to pad height. This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. Check out the Westshore Marine & Leisure Youtube page! This, however, is not recommended for the beginning boater. He is also a certified marine technician and the author of a popular text on writing local history. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. If the height of the boat transom is off it can cause major issues. The faster your boat, the more critical it is to get the sizing just right. The greater the number, the more the drive may sway (also called tuck under or negative trim). Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. The distance between the ends of a transom is measured in inches. Gear Oil Quantity 195ml(6.6 Fl.oz.) minAmount: 300.0, 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). Because of the increased friction, cavitation reduces efficiency. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. Other boats that need long shafts are. Its still smart to measure it yourself though, just in case, the design changed over the years. 3 0 obj function mpeInit() { Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. Boats with extended transoms, brackets that extend the mounting bracket for the outboard motor behind the back of the boat, can use a higher outboard height. For slower boats, its less critical to. The cookie is used to store the user consent for the cookies in the category "Performance". C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? (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. As with anything, there are exceptions to the rule. Beginning boaters should be aware of the boats measurements. Before we get started lets see what a boat transom is and what it does. Outboard shaft length plays a crucial role in the performance of your boat. Here we will guide you in how to get the right boat transom height. Here we look at the effects of standard, lower and higher mounting. The height is approximately six inches higher than with a propeller. Long shafts are 20-inches long. With the long side (22 1/2), place a carpenters square ) in opposition to the keel. Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. The correct shaft length for your boat depends on a few factors. This provides seaworthiness and offers maximum protection from large seas. A yardstick will help you determine if your outboard engine is at the right height. These are vertically aligned so the boater can make adjustments. Two years ago, I bought a Boston Whaler to fish off the coast. The clamp bracket on the latest Mercury Four-Stoke-model outboards has five mounting bolt holes spaced .75 inches apart. When you measure the width of the stern, mark the center with a grease pencil. <>/Metadata 127 0 R/ViewerPreferences 128 0 R>> The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. Expectedly, when the transom angle is zero, it means it is flat. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. The transom is the back of the boat where the motor is hung. The motor is what powers the boat so the two go hand-in-hand. In the photo above, we've measured from the motor bracket to the top of Take your time and understand your boat and your entire transom. A big NO. It is extremely important that the boater understands the significance of the transoms height. Again, make sure that you are measuring to the flat part of the brackets; (function (d) { Triton. Which Navigation Lights Does Your Boat Need? The transom is the flat vertical section at the rear of the boat. steel ruler, etc. With some boats I have a pretty good idea as to what length motor should be hung on them. Re: Dinghy with a long shaft motor? Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Outboard Motor Shaft Length: How do I measure? This, however, is not recommended for the beginning boater. Measure the area of the transom directly where the engine will be mounted. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. These cookies will be stored in your browser only with your consent. 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. The transom angle is the vertical incline of the transom and is measured in degrees. Read the measurement on the transoms bottom. 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. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; 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. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. 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. Or it can have an angle degree as high as 30. Since the length of the shaft of your outboard is associated with the size boat, smaller engines will generally have shorter shafts.