how to measure transom height for outboard motor

The cookie is used to store the user consent for the cookies in the category "Performance". Whats the best height for my boat motor? What are Apple Podcasts Subscriptions and Channels? The transom is the flat vertical section at the rear of the boat. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. Cavitation plates are used on the bottom components of boats to help them operate better. If the height of the boat transom is off it can cause major issues. 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. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. Among them will be first-timers or those who have recently purchased their boats. Other factors to consider when determining the mounting height of an outboard are related to performance. priceSelector: ".price--withoutTax, span.price.price--withTax", if (PayTomorrow) { This measurement was approximately 4". 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. 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. Read the measurement on the transoms bottom. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. (Putting a Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. Or measure from the main engine prop up to the water line? Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Re: Dinghy with a long shaft motor? minAmount: 300.0, One of the great things about an outboard motor is how versatile it is. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". <> Check out the full chart of the Mercury outboard model code and its features. Then open up the clamp bucket. There are instances where a lower mount may be okay. 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. bassboat can be a bit confusing at times; hopefully this will help sort Actual shaft length is 21.5" on those. If you went too long it would still work but it may lack in performance. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. 7. 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. If it measures between 17 and 22, you'll want to go with a long shaft motor. 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. To break it down a bit more for you: Short shafts are 15-inches long. Before we get started lets see what a boat transom is and what it does. However, you will need an understanding of how the degrees will alter the boats usability. var BCData = {"csrf_token":"d7ecb6b56891bb66aee12dbc01a80162b3ed582c1acbe30f16fc9f1b2abc362f"}; They operate as a planing surface, allowing your boat to climb to the top more quickly. Safely but briskly accelerate. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. Simply start with the engine in idle, followed by, If you decide to make some custom adjustments we have the. As summer approaches there will be more boaters taking to the water. Measure from the top of the transom to the bottom of the hull. Read the following to get the optimal shaft length for outboard motors! 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. Recommended Engine Oil 2-Stroke Outboard Motor Oil. As summer approaches there will be more boaters taking to the water. I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. measuring; you may have to "extend" the flat part of the But, how do you measure it? Look at the part of your motor that would be To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. 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). Smaller 12-14 foot boats can require either a short or long shaft outboard depending on the style of the boat and the brand. Boaters who consider going with a higher mount can see increased speeds. 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. If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. 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. If you have an outboard motor, the distance from one end to another will be found on the side or on a label near its bottom. It also includes attaching the right engine. This is measured by the propeller shaft being parallel to the vessels bottom. Also, how do you determine the length of an outboard transom? If you have a question or need additional information,contact ustoday. 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. As a yacht designer and boater, I prefer longer shafts. of the "bullet" on your lower unit. This measurement is primarily designed for single motor propulsion. The transom is the back of the boat where the motor is hung. Because of the increased friction, cavitation reduces efficiency. For example, you can have the Mercury outboard shaft length by model code. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. Pad to bottom of Another important measurement is the transom angle. boats.com is part of the Boats Group Network. 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. Outboard Motor Shaft Length: How do I measure? Triton. If you decide to make adjustments, please consult a marine engine dealer about the boat design. 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. Whether you already own a boat or looking for your first watercraft we are here to service your needs. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. You can find your Mercury outboard model code on an ID plate or sticker. It moves an outboard up and down to optimize performance and enable a boat to venture into shallower water than it might otherwise. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. s.setAttribute("rel", "stylesheet"); It is where the outboard is mounted, and some boat owners place the name of the boat. The propellers will also have trouble reaching the water. 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. Keith Allen, a 1979 graduate of Valley City State College, has worked at a variety of jobs including computer operator, medical clinic manager, radio talk show host and potato sorter. So from there, I will try to help out by asking questions about your boat such as what type it is and the length. loadScript(ptScript); Depending on the manufacturer, size names might change. Knowing how this can affect the overall operation of the boat is a factor to be considered. Your email address will not be published. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. The shaft length for outboard motors has nothing to do with the water line. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. It will ensure that the outboards trim will be effective, and it will save you gas too. Save my name, email, and website in this browser for the next time I comment. The transom is the rear wall of the boat where the outboard engine is mounted in the middle. bracket. Copyright 1999-2023 Boats Group. What Kind of Fuel Does Your Marine Engine Need? function loadScript(script) { Buying a boat can be an exciting purchase. There are instances where a lower mount may be okay. 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. var h = d.getElementsByTagName("head"), Later in the article is an image that shows you exactly where to measure. 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. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. 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). Smaller boats may use adjustable jack plates that can be changed to fit any outboard. This website uses cookies to improve your experience while you navigate through the website. With the long side (22 1/2), place a carpenters square ) in opposition to the keel. However, your boat will have slightly more drag which will reduce your maximum speed. Workboats, sailboats, and displacement-hulled boats fall into this category. Your email address will not be published. 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. My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. This could also effect your travelling capabilities on the boat trailer. How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. var xmlHttp = new XMLHttpRequest(); Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. Is my outboard long or short shaft? The transom is the flat vertical section at the rear of the boat. and I'll explain it better, (or point you to someone that can help. With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. The amount of degrees the transom leans back from vertical is known as the transom angle. ), Al Shields Like Westshore Marine & Leisure on Facebook! (function (d) { endobj 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. If your boat planes, pay extra attention to getting the shaft length as close to perfect as possible. h[0].appendChild(s); When fighting waves from the stern, a 20-inch transom is considerably safer. Take a long straight edge, (long carpenter's level or long 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. If it measures between 17 and 22, youll want to go with a long shaft motor. var prefix = 'ma' + 'il' + 'to'; Most of the standard engined boats it takes shafts that are 15-30inches long. 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. Where Onboard a Boat is the Transom Located and More About Transom Heights A propeller operates based on the height of the transom. Another important measurement is the transom angle. This alone can outweigh the negatives when deciding to adjust the mount upwards. You reply, "Im not sure, I think its a long". You also might not be able to lift the outboard out of the water entirely for storage. Any questions? All things considered, sticking with the industry standard is best for the beginner. What the relationship to the pontoons is, I couldn't say. Well, raising the outboard motor can be an easy task for you. Many single-engine boats mount a smaller auxiliary motor for emergency use. But opting out of some of these cookies may affect your browsing experience. 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? It can also improve the experience of driving a faster boat. 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. 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. Expectedly, when the transom angle is zero, it means it is flat. jackplate to a point level with the top of the transom. Make sure that you are measuring straight up, at a 90 degree angle to Industry standards dictate that for short shaft engines the transom height should be 15. Step 2: Three Variables to Consider However, you will need an understanding of how the degrees will alter the boats usability. Extra-long shafts are 25-inches long. primeApr: 12.99, In the case of a larger offshore boat, it may be to the top of a cutout on the . If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. You can use a longer shaft than recommended and your boat will work fine. If the height of the boat transom is off it can cause major issues. disregard the downward pointing "hooks" at the front of the If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. All things considered, sticking with the industry standard is best for the beginner. Higher mounting decisions should be left to the professionals. 2 0 obj 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. 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. C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? not sure that it's still used. This is somewhat similar to #2, in that you are again measuring with a 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}'); So you should just measure the height of the boat's transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. You can order an outboard in lengths ranging from 15 inches to 30 inches, depending on its power output and possible uses. Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. "brackets". 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. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. 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. Spark Plug 25.0nm(18.4 Ft-lb) (2.55 Kgf-m) Boaters who consider going with a higher mount can see increased speeds. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. It also cuts into speed and fuel efficiency. straight edge from the center of the pad, but this time you're measuring We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. 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. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Or it can have an angle degree as high as 30. Having the cavitation plate a bit lower than the transom is preferable to having it too high. AztH ^zv_ cT,E1K/rAB54| If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). 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. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. I mean it is better to be safe than sorry, am I right? *The Factors indicates the adjustment affected by on your boat type, the outboard working environment, and the transom distance as discussed above. So its easier and safer to communicate with the dealer with the exact measurement of outboard shaft length in order to get the right model. s.setAttribute("href", "https://cdn.paytomorrow.com/css/pt-mpe.min.css"); A reverse transom that sits too high can impact the propellers of the motor and motor bracket. If your outboard motor height. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. Tilt your motor until the bullet of the gearcase is The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. 3 0 obj window.dataLayer = window.dataLayer || []; As a result, the issue is whether my boat need a short shaft or long shaft motor. want to measure from the transom to the flat part of this bracket, This is a measurement that has been used for BassCats, I'm The average transom angle is around 14 degrees. Industry standards dictate that for short shaft engines the transom height should be 15. motor brackets Then adjust the motor in a higher hole with a flat head screwdriver. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. Required fields are marked *. Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. You will also risk hitting bottom or submerge objects more frequently such as rocks or logs. On the downside, a higher mount can interfere with the boaters steering capabilities. What Types of Documents Can be Sent to your Kindle Library? publicId: "32bf3437d1346295e03ebcf545f9c839", 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. %PDF-1.7 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. Engine Oil Type Genuine or Recommended 2str Engine Oil. Tightening Torque for Engine. Upstream Securitys Disruptive Telematics Technology, The challenges of scaling a cloud-based security system, OneStreams unified platform streamlines financial data management, OneStreams impact on the financial software market. The motor is what powers the boat so the two go hand-in-hand. Place the point of a yardstick at the middle of the top of the boat transom. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. High powered boats usually only come in long and extra-long variants. This measurement would be the inches of PayTomorrow.mpeInit({ 5/rC,aQhsK@Q. You'll need a short shaft outboard if it's 15 or less than an inch shorter. The boat transom can be flat with zero degree angles. I would ask you to go back and measure the transom of your boat. Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. 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. The same is true for the newest, high-powered offshore fishing boats, where triple or quadruple motor setups are becoming more and more common. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! It is very versatile as it generally . In the case of a dinghy or johnboat, this point may be the top of the transom. 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. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. Since the ventilation plate & foil are burried under water it is obviously too low. See diagram below. Then test the boat and adjust the height, if necessary . What is Transom Height? Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. 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. Thats it. This cookie is set by GDPR Cookie Consent plugin. For slower boats, its less critical to. This also means it can affect the safety of the boat. (3) Move horizontally across the chart until you hit the graph curve. Some fishing boats can handle the motor being underwater. Shaft lengths are available in increments of 5. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. This would not be a good thing. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. s = d.createElement("link"); With this in mind, how can I determine if my outboard has a short or long shaft? 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. h[0].appendChild(s); The height of the boat transom dictates the size of the 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. You dont have to be a mathematician to determine the correct boat transom angle. This cookie is set by GDPR Cookie Consent plugin. If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. All you need to do is measure how much to rise. The motor is what powers the boat so the two go hand-in-hand. An outboard motor can drive just about any sort of boat with proper mounting. See When St. Peters Basketball Games Are Today! These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. It varies between different motors and boats. }, 100); A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Displacement hulled vessels like sailboats and workboats can benefit from a little more space between the hull and cavitation plate, but not much. The brackets can add 1 inch to the overall mounting height of the outboard. Before we get started lets see what a boat transom is and what it does. Most of the time, adding a hydrofoil to an outboard improves performance. Other boats that need extra long shafts are: Read my other articles on outboard motors. Mounting the outboard motor in accordance with the industry standards is important. 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. In addition, motor totes will not harm the finish of the lower unit. This is handy if youre shopping for second-hand outboards or looking to sell the one that came with your boat. 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. You also have the option to opt-out of these cookies. Should I take the raft onto the water and measure the exact distance from the top of the transom to the water line? A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. s.setAttribute("type", "text/javascript"); Beginning boaters should be aware of the boats measurements. Anything bigger than that your obviously going to need an extra long shaft. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. relation to pad How high exactly do you have to raise the transom?-. Determining Your Boat Transom Angle The transom angle - commonly measured in degrees - is the transom's vertical inclination. And the rule of thumb is that you should keep the cavitation plate level with the bottom or keel of the boat. x\[D~OUCO6[j](l%ay <8cylY{.L2s#]~U6A|Wj]-oo|mubqY6wbY_|!>Z8(RB:RHeTzOGO_=~t\ Doing this can have adverse effects. This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. The clamp bracket on the latest Mercury Four-Stoke-model outboards has five mounting bolt holes spaced .75 inches apart. Knowing how this can affect the overall operation of the boat is a factor to be considered. 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? Finding the right size is a matter of looking at what youve got and taking out the measuring tape. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft.

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