how to measure transom height for outboard motor

<> Should I take the raft onto the water and measure the exact distance from the top of the transom to the water line? Triton. Copyright 1999-2023 Boats Group. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. Outboard Motor Shaft Length & HP to Boat Calculating would be more accurate.) High powered boats usually only come in long and extra-long variants. Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Some boats are equipped with transom-hung outboards while others have a bracket. 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. How to Measure Outboard Shaft Length: The Only Guide You Need <> (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) The transom angle is the vertical incline of the transom and is measured in degrees. Step 4. The transom is the back of the boat where the motor is hung. Long shafts are 20-inches long. Other factors to consider when determining the mounting height of an outboard are related to performance. The transom angle is the vertical incline of the transom and is measured in degrees. out the confusion. All rights reserved. If it measures 15" or with in a inch of that you will need a short shaft outboard. It varies between different motors and boats. The general guideline for longer shaft outboards is that the transom height should be at least 20 inches (50,8cm) above the waterline. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. With some boats I have a pretty good idea as to what length motor should be hung on them. xmlHttp.setRequestHeader('Content-Type', 'application/json'); 7. You may wonder how deep your prop should be in the water. 4 0 obj There are a series of four to six holes at the top of the bracket, and the lower bolts actually fit into slots. This website uses cookies to improve your experience while you navigate through the website. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. With the outboard shaft length too long, meaning the prop is too deep in the water, the engine wont be as efficient, and the fuel burn is high. Variables to consider when determining the mounting height include the size and style of the boat and the length of the outboard motor's shaft. The cookie is used to store the user consent for the cookies in the category "Analytics". Check out the Westshore Marine & Leisure google plus page! The motor is what powers the boat so the two go hand-in-hand. Boat Transom Heights - The Beginner's Guide | My Westshore 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. 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. For most boaters this is a no brainer, but for the novice or inexperienced boater it may be a tougher question. It was a 23-foot Crestliner Grand Cayman pontoon boat. AztH ^zv_ cT,E1K/rAB54| Simply start with the engine in idle, followed bytrimming the motor out by one-half to full trim. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. 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. Check out the Westshore Marine & Leisure Youtube page! 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. former editor at Boating Magazine and contributor to many national publications 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. It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. 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. Expectedly, when the transom angle is zero, it means it is flat. Increased RPM and additional horsepower feed the need for speed. You can order an outboard in lengths ranging from 15 inches to 30 inches, depending on its power output and possible uses. Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. Recommended Engine Oil 2-Stroke Outboard Motor Oil. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". Because of the increased friction, cavitation reduces efficiency. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. Mounting kicker motor - General Discussion Forum | In-Depth Outdoors Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. In lower mounting, the engine is set lower than the recommended standard. Many single-engine boats mount a smaller auxiliary motor for emergency use. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. How to Measure Shaft Length on Outboard Motor? - TrollinMotorsGuide Tilt your motor until the bullet of the gearcase is All rights reserved. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. How the outboard will sit on the back of the boat depends on how the transom is designed. Read the following to get the optimal shaft length for outboard motors! If the height of the boat transom is off it can cause major issues. 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. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. These cookies will be stored in your browser only with your consent. Increased RPM and additional horsepower feed the need for speed. You reply, "Im not sure, I think its a long". (Any measurement given as "off the transom" When you measure the width of the stern, mark the center with a grease pencil. your motor will be higher.) Actually there is no designated letter for short shaft. Knowing how this can affect the overall operation of the boat is a factor to be considered. As with anything, there are exceptions to the rule. Make sure that you are measuring straight up, at a 90 degree angle to What's the best height for my boat motor? Later in the article is an image that shows you exactly where to measure. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. motor brackets Using your existing control box and gauges will save you quite a bit of money in the end. Mounting the outboard motor in accordance with the industry standards is important. How do you measure a transom on an outboard motor? and I'll explain it better, (or point you to someone that can help. Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. In addition, motor totes will not harm the finish of the lower unit. The boater must also consider if the boat transomsupport is designed to bear the weight of a higher mount. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. (function () { If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. This is probably the worst case scenario out of the two. At least if its too long you can raise the motor or "build up" your transom. The engine must be linked to the transom at the proper height for a propeller to best meet specific boating demands. parallel with the straight edge. |. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. jackplate to a point level with the top of the transom. However, your boat will have slightly more drag which will reduce your maximum speed. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. 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. All boats are different, and the motor manufacturers produce a variety of standard lengths. These allow the mounting of a standard length outboard behind the transom. When fighting waves from the stern, a 20-inch transom is considerably safer. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. The height of the boat transom dictates the size of the outboard motor. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. Actual shaft length is 21.5" on those. Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. The form of a boats transom varies depending on the manufacturer and model. Your email address will not be published. How To Measure Outboard Motor Shaft Length [Long v Short] - Boating Hub Proper Mounting Height for an Outboard - Gone Outdoors All things considered, sticking with the industry standard is best for the beginner. 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. Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. Tightening Torque for Engine. 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. You 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. 12 Small Fishing Boat Accessories to Buy Today. ), Al Shields Industry standards dictate that for short shaft engines the transom height should be 15. Outboard shaft length plays a crucial role in the performance of your boat. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. } Higher mounting decisions should be left to the professionals. To achieve this, the motor itself has to be attached at the correct height. enableMoreInfoLink: true, 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. As mentioned above, the operation of the propeller relies on the transom height. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. 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. 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. 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. 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. Then adjust the motor in a higher hole with a flat head screwdriver. 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. bracket forward with a straight edge to where you can then measure up Measure the area of the transom directly where the engine will be mounted. Take your time and understand your boat and your entire transom. Required fields are marked *. Boats with more engine power and weight require longer shaft outboards for better balance. Will Charpentier is a writer who specializes in boating and maritime subjects. This is simply a measurement taken from the top of the transom (top of The how to measure the shaft length of an outboard motor is a question that many people have asked. 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). 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. Learn More About Your Boats Systems By Joining The Born Again Boating Academy! 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. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. August 9/08). function gtag(){dataLayer.push(arguments);} h[0].appendChild(s); However, the motor should not be raised more than 5 inches above the standard position. 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. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. Before we get started lets see what a boat transom is and what it does. This cookie is set by GDPR Cookie Consent plugin. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. 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 mounting height of the outboard engine is the equivalent of the distance between the base of the motor and the top of the propeller. The transom in a boat today is a place to hang your outboard motor. This restriction includes most fishing boats and longer sailboats. The height is approximately six inches higher than with a propeller. PayTomorrow.mpeInit({ Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. straight edge on the top of the transom to "extend" it out How To Mount An Outboard Motor Properly - Start to Finish! Always weigh the risks of making adjustments. The height of the boat transom dictates the size of the outboard motor. storeDisplayName: "Marine Parts Warehouse", maxTerm: 36, This cookie is set by GDPR Cookie Consent plugin. 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". The pressure behind your hand dropped as you slid your hand back and forth through the water. This would not be a good thing. An inch or two probably wont make a big difference, but any more than that will lead to trouble. x\[D~OUCO6[j](l%ay <8cylY{.L2s#]~U6A|Wj]-oo|mubqY6wbY_|!>Z8(RB:RHeTzOGO_=~t\ (127 mm). | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ A transom saver, which can change the spacing between the lower unit and the trailer, negates some of the support. 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 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. Other boats that need extra long shafts are: Read my other articles on outboard motors. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. The same is true for the newest, high-powered offshore fishing boats, where triple or quadruple motor setups are becoming more and more common. measuring; you may have to "extend" the flat part of the 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. With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. Thats it. Engine Oil Type Genuine or Recommended 2str Engine Oil. The cookie is used to store the user consent for the cookies in the category "Performance". Before we get started lets see what a boat transom is and what it does. boats.com is part of the Boats Group Network. The clamp bracket on the latest Mercury Four-Stoke-model outboards has five mounting bolt holes spaced .75 inches apart. Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. 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. I hope this helps someone out in their search for a new or newer outboard this season. Use the mounting bracket on the motor to know where it will sit on the boat. Another important measurement is the transom angle. This exhaust port should be about 1 inch above the water line when the boat is idling. publicId: "32bf3437d1346295e03ebcf545f9c839",

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