how to measure transom height for outboard motor

maxMicroAmount: 0.0, Other boats that need extra long shafts are: Read my other articles on outboard motors. What Kind of Fuel Does Your Marine Engine Need? If the height of the boat transom is off it can cause major issues. On the downside, a higher mount can interfere with the boaters steering capabilities. Place the rulers end on the ground behind the club and let the club to rest on top of it. Over time, Boating Hub has grown into a resource for boating enthusiasts around world. Boaters who consider going with a higher mount can see increased speeds. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. Copyright 1999-2023 Boats Group. Check out the Westshore Marine & Leisure Youtube page! Each one has a totally different effect on the boats performance. 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 transom is the flat vertical section at the rear of the boat. Use the mounting bracket on the motor to know where it will sit on the boat. The average transom angle is around 14 degrees. 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. %PDF-1.7 var prefix = 'ma' + 'il' + 'to'; These cookies ensure basic functionalities and security features of the website, anonymously. There is a simple test to see if your outboard motor is set at the best height. Where Onboard a Boat is the Transom Located and More About Transom Heights A propeller operates based on the height of the transom. Look at the part of your motor that would be His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. Other factors to consider when determining the mounting height of an outboard are related to performance. Depending on the manufacturer, size names might change. A big NO. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. 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. However, there may be times when a boater strays away from these recommendations. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. Save my name, email, and website in this browser for the next time I comment. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. Buying a boat can be an exciting purchase. Necessary cookies are absolutely essential for the website to function properly. Read the following to get the optimal shaft length for outboard motors! 4 0 obj Place the point of a yardstick at the middle of the top of the boat transom. (Any measurement given as "off the transom" Allowing the propeller to pull water from underneath and push it out behind the boat. The transom angle is the vertical incline of the transom and is measured in degrees. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. This cookie is set by GDPR Cookie Consent plugin. I mean it is better to be safe than sorry, am I right? up to the bottom of the motor brackets, (as in #1). |. An outboard motor can drive just about any sort of boat with proper mounting. Boaters who consider going with a higher mount can see increased speeds. If it measures 15" or with in a inch of that you will need a short shaft outboard. If you go too short your more than likely going to cavitate and loose power. (127 mm). There are also specialty motor shaft lengths. Because of the increased friction, cavitation reduces efficiency. ), and place it on the bottom of the pad in the center. So how to measure outboard shaft length? Always weigh the risks of making adjustments. All you need to do is measure how much to rise. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. All things considered, sticking with the industry standard is best for the beginner. Propshaft in 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. This would not be a good thing. The boat transom can be flat with zero degree angles. What is Transom Height? The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. Some boats are equipped with transom-hung outboards while others have a bracket. stream jackplate to a point level with the top of the transom. 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. Happy boating! will be to the flat part; if you measure to the bottom of the brackets Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Outboard Motor Shaft Length: How do I measure? As summer approaches there will be more boaters taking to the water. disregard the "hooks" at the front of the They operate as a planing surface, allowing your boat to climb to the top more quickly. Boats that use longer outboard shafts include: (3) Move horizontally across the chart until you hit the graph curve. If so, send me an 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. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. 2019s List of the Best Recreational Pontoon Boats for Sale. Some outboards have a serial number that tells you which shaft length to go for. 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. Gear case sits just below or at the hull depth due to the deep v. If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. Always weigh the risks of making adjustments. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. How Transom Height Is Measured }) } }); })(document); Buying a boat can be an exciting purchase. For slower boats, its less critical to. debugMode: false, Some fishing boats can handle the motor being underwater. 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? It will ensure that the outboards trim will be effective, and it will save you gas too. Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. s = d.createElement("script"); This measurement would be the inches of Ten years ago I bought my first boat. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. There are 2 steps to help get a relatively accurate figure. You'll need a short shaft outboard if it's 15 or less than an inch shorter. Pad to bottom of ensure that your measurement is accurate. s.setAttribute("src", script); s.setAttribute("type", "text/javascript"); function gtag(){dataLayer.push(arguments);} Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. To sum up, there is a simple calculator of the shaft length for outboard motors: Outboard Shaft Length = Transom Height +/- Factors. 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. 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. 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. would be more accurate.) You need JavaScript enabled to view it. 1 0 obj A2: Instead of changing to the short outboard shaft, you can try the Jack Plate first. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). It varies between different motors and boats. Mounting the motor lower on the boat transom can create excessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. 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 pros and cons of properly . 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". It also includes attaching the right engine. Wherever the outboard clamping bracket is, use this as the basis for measurement. August 9/08). In the photo above, we've measured from the motor bracket to the top of (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. mpeSelector: ".pt-mpe", MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. (updated Theyre also useful if the back of your boat has a non-standard measurement. Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. 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 with anything, there are exceptions to the rule. 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. 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. Which Navigation Lights Does Your Boat Need? I would ask you to go back and measure the transom of your boat. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. In lower mounting, the engine is set lower than the recommended standard. Industry standards dictate that for short shaft engines the transom height should be 15. 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. Here we will guide you in how to get the right boat transom height. Then finally test your outboard, if the mount is perfect. This allows the engine to idle without the flow of the exhaust being restricted. This, however, is not recommended for the beginning boater. 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. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. A reversetransom that sits too high can impact the propellers of the motor and motor bracket. Then open up the clamp bucket. You may wonder how deep your prop should be in the water. The faster your boat, the more critical it is to get the sizing just right. 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). The same is true for the newest, high-powered offshore fishing boats, where triple or quadruple motor setups are becoming more and more common. Since the length of the shaft of your outboard is associated with the size boat, smaller engines will generally have shorter shafts. Measure straight down to the lowest point on the hull. If your outboard motor height. The height of the boat transom dictates the size of the outboard motor. actually have the propshaft above the pad.). C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? The propellers will also have trouble reaching the water. It was a 23-foot Crestliner Grand Cayman pontoon boat. 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. 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 boat transom can be flat with zero degree angles. var addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@' + 'vanssports' + '.' + 'com';document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML += ''+addy_textd53b59933f6c3f2e8b59f1b4a6d41fa5+'<\/a>'; In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. This was the height of my 225 Yamaha on my TR21 It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. 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. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; Gear Oil Quantity 195ml(6.6 Fl.oz.) For example, you can have the Mercury outboard shaft length by model code. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. These cookies track visitors across websites and collect information to provide customized ads. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. to where the brackets were actually resting on the transom. 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. In the second photo, we've measure down from the top of the Detwiler since 1986. You dont have to be a mathematician to determine the correct boat transomangle. Increased RPM and additional horsepower feed the need for speed. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. This alone can outweigh the negatives when deciding to adjust the mount upwards. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. It can also improve the experience of driving a faster boat. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. Doing so, will put the propeller right below the boat. Outboards designed for saltwater applications usually have longer shafts. Other boats that need long shafts are. xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. Step 2: Three Variables to Consider This is measured by the propeller shaft being parallel to the vessels bottom. 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. 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 also have the option to opt-out of these cookies. It is unsafe to have the engine block too close to the water on a low transom. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. 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. Save my name, email, and website in this browser for the next time I comment. Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. What is the Virtual Sundance Film Festival? } h[0].appendChild(s); On the downside, a higher mount can interfere with the boaters steering capabilities. The outboard comes with mounting holes and brackets. If the propeller fails to ventilate, the motor is mounted to low. Get the latest updates on new products and upcoming sales, 2023 Marine Parts Warehouse Incorporated Take your time and understand your boat and your entire transom. If you are running a twin-engine setup, then measure the same distance from each clamping plate to the bottom of the hull. To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). endobj As with anything, there are exceptions to the rule. Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. 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. The motor is what powers the boat so the two go hand-in-hand. This is measured by the propeller shaft being parallel to the vessels bottom. As a result, the issue is whether my boat need a short shaft or long shaft motor. Its where the outboard motor is attached, and its also where some boat owners put the boats name. Many single-engine boats mount a smaller auxiliary motor for emergency use. As you can see, the measurement is about 2 1/2". Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. 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. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. For most boaters this is a no brainer, but for the novice or inexperienced boater it may be a tougher question. 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. The most common percent angle is probably 12, however spec sheets for O/B and I/O boats may show 10 percent, 12 percent, and 14 degrees. As mentioned above, the operation of the propeller relies on the transom height. For over five years he has worked as a newspaper reporter and historic researcher. Among them will be first-timers or those who have recently purchased their boats. Of course, its always best to go with standard practices when choosing thebest boat engine. The first order of business is to measure your boat for the ideal fit. var xmlHttp = new XMLHttpRequest(); Small portable outboards ranging from 2 to 20 horsepower are usually sold only in short or long shaft versions. Determining Your Boat Transom Angle The transom angle - commonly measured in degrees - is the transom's vertical inclination. This is handy if youre shopping for second-hand outboards or looking to sell the one that came with your boat. As summer approaches there will be more boaters taking to the water. You dont have to be a mathematician to determine the correct boat transom angle. You The brackets can add 1 inch to the overall mounting height of the outboard. 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. out the confusion. #1: Height Most transom savers can support up to a 150HP motor, which is sufficient for most regular boats. If it measures between 17 and 22, you'll want to go with a long shaft motor. Workboats, sailboats, and displacement-hulled boats fall into this category. See diagram below. What types of boat need an extra long shaft? 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 boater must also consider if the boat transom support is designed to bear the weight of a higher mount. The Effects of Standard, Lower and Higher Mounting. What matters is the actual measurement in the specifications, not the name. 12 Small Fishing Boat Accessories to Buy Today. Using your existing control box and gauges will save you quite a bit of money in the end. Extra-long shafts are 25-inches long. Basically, there are three main ways to measure motor 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. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; He is a 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. function mpeInit() { Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. Spark Plug 25.0nm(18.4 Ft-lb) (2.55 Kgf-m) MPW eBay Store - Thousands of New OEM Old Stock Parts! Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. 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. 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. Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. Mounting the outboard motor in accordance with the industry standards is important. The height of the boat transom dictates the size of the outboard motor. You need JavaScript enabled to view it. By clicking Accept, you consent to the use of ALL the cookies. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. As mentioned above, the operation of the propeller relies on the transom height. 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. Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? These are vertically aligned so the boater can make adjustments. To achieve this, the motor itself has to be attached at the correct height. s.setAttribute("href", "https://cdn.paytomorrow.com/css/pt-mpe.min.css"); I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. 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.

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