how to measure transom height for outboard motor

center of the propshaft. So you should just measure the height of the boats transom from the center down to the lowest point of the hull, and compare transom height with the outboard shaft length numbers. Industry standards dictate that for short shaft engines the transom height should be 15. 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. How Transom Height Is Measured Typical motor lengths include the following. Beginning boaters should be aware of the boats measurements. Having the cavitation plate a bit lower than the transom is preferable to having it too high. *The Factors indicates the adjustment affected by on your boat type, the outboard working environment, and the transom distance as discussed above. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. displayMicroOffers: false, priceSelector: ".price--withoutTax, span.price.price--withTax", Any questions? Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. Higher mounting decisions should be left to the professionals. If you have a question or need additional information,contact ustoday. A deep Vee hull will result in a different measurement than a flatter . What matters is the actual measurement in the specifications, not the name. Add yours in the comment and Ill get back to you asap. Always weigh the risks of making adjustments. In lower mounting, the engine is set lower than the recommended standard. AztH ^zv_ cT,E1K/rAB54| mpeInit(); This will be the When fighting waves from the stern, a 20-inch transom is considerably safer. See diagram below. endobj By clicking Accept, you consent to the use of ALL the cookies. The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. Then adjust the motor in a higher hole with a flat head screwdriver. It is extremely important that the boater understands the significance of the transoms height. Use the mounting bracket on the motor to know where it will sit on the boat. Among them will be first-timers or those who have recently purchased their boats. 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. var addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@'; We also use third-party cookies that help us analyze and understand how you use this website. Figuring out how to measure motor height on a 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. To do so, measure from the stern (back) of the boat to the midpoint of the hull on both sides. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. actually have the propshaft above the pad.). 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 height of the transom is calculated by measuring from the bottom of the hull to the top of the transom, using the center line. var ptScript = "https://cdn.paytomorrow.com/js/pt-mpe.min.js"; 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. 1855 Alpine Avenue NWGrand Rapids, MI 49504This email address is being protected from spambots. Tilt your motor until the bullet of the gearcase is Check out the Westshore Marine & Leisure google plus page! His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. Then finally test your outboard, if the mount is perfect. 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. 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. The height is approximately six inches higher than with a propeller. Workboats, sailboats, and displacement-hulled boats fall into this category. h[0].appendChild(s); As a dealer I run into this situation from time to time, which is fine but getting the right length outboard for your boat is crucial. Rest the yard stick or another suitable straight edge along the keel on the bottom of the boat so that it makes a straight line aft to the outboard. I live for the weekends when I can go out on the water and escape the stress of life on land. An outboard motor can drive just about any sort of boat with proper mounting. Place the bracket on the transom to the left of the main outboard or rudder. Boats with more engine power and weight require longer shaft outboards for better balance. <> motor brackets Read the measurement on the transoms bottom. the propshaft below or above the pad. 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. measuring; you may have to "extend" the flat part of the 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 height of the transom is calculated by measuring from the bottom of the hull to the top of the transom, using the center line. He is a loadScript(ptScript); This website uses cookies to improve your experience while you navigate through the website. See When St. Peters Basketball Games Are Today! One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. 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. It is where the outboard is mounted, and some boat owners place the name of the boat. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. The distance between the ends of a transom is measured in inches. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Is my outboard long or short shaft? Take your time and understand your boat and your entire transom. When the boat transom is too low, the motor could end up underwater. The clamp bracket on the latest Mercury Four-Stoke-model outboards has five mounting bolt holes spaced .75 inches apart. Cavitation plates are used on the bottom components of boats to help them operate better. 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. Buying a boat can be an exciting purchase. This would not be a good thing. These cookies track visitors across websites and collect information to provide customized ads. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. Well, raising the outboard motor can be an easy task for you. stream Whether you already own a boat or looking for your first watercraft we are here to service your needs. It also cuts into speed and fuel efficiency. Take your time and understand your boat and your entire transom. All boats are different, and the motor manufacturers produce a variety of standard lengths. maxAmount: 6500.0, not sure that it's still used. would be more accurate.) 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. 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. Why Rebounding Is A Key Skill for Fouth Players To Learn, Tips For Attacking a Zone Defense as a Youth Basketball Team, Why This is a Big Deal for the Sports Betting Industry. a Detwiler manual jackplate. What are Apple Podcasts Subscriptions and Channels? 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. var h = d.getElementsByTagName("head"), Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. Engine Oil Type Genuine or Recommended 2str Engine Oil. Doing so, will put the propeller right below the boat. This, however, is not recommended for the beginning boater. The outboard comes with mounting holes and brackets. The amount of degrees the transom leans back from vertical is known as the transom angle. The transom is the flat vertical section at the rear of the boat. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. (616) 364-0666, On all contiguous US part orders over $100. var prefix = 'ma' + 'il' + 'to'; Repowering your boat is one of the most expensive upgrades you can make. What Types of Documents Can be Sent to your Kindle Library? If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. Check out the full chart of the Mercury outboard model code and its features. I also love helping others, which is why I created this website. Thats it. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. (3) Move horizontally across the chart until you hit the graph curve. 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 first step is to determine the height of your boat's transom. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. s.setAttribute("rel", "stylesheet"); If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. I mean it is better to be safe than sorry, am I right? As mentioned above, the operation of the propeller relies on the transom height. Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". If you said something smaller than that, thats where it can get tricky. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. Theyre also useful if the back of your boat has a non-standard measurement. 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. #3. Knowing how this can affect the overall operation of the boat is a factor to be considered. (In the case of the faster straight edge from the center of the pad, but this time you're measuring There is a simple test to see if your outboard motor is set at the best height. It is where the outboard is mounted, and some boat owners place the name of the boat. Gear case sits just below or at the hull depth due to the deep v. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> 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. Later in the article is an image that shows you exactly where to measure. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; Many single-engine boats mount a smaller auxiliary motor for emergency use. Each one has a totally different effect on the boats performance. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. They operate as a planing surface, allowing your boat to climb to the top more quickly. 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). d.addEventListener("DOMContentLoaded", function (e) { out the confusion. This cookie is set by GDPR Cookie Consent plugin. As mentioned above, the operation of the propeller relies on the transom height. On this type of boat, if you are in doubt, default to the longer-shafted outboard. If it measures 15" or with in a inch of that you will need a short shaft outboard. to where the brackets were actually resting on the transom. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. For example, you can have the Mercury outboard shaft length by model code. If you have a jackplate, you may have to get a bit creative in your 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. ), Al Shields However, you will need an understanding of how the degrees will alter the boats usability. (updated Disclaimer: As an affiliate I may earn a commission on any qualifying purchases, including those from Amazon.com, at no extra cost to you read more. 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. No matter what size of boat you are running, one of the most critical choices you can make when buying an outboard motor is the shaft length. s = d.createElement("script"); If you are running a slower boat, the exact location of the ventilation plate is less important. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. When mounting the engine, you want the cavitation plate to be 1 above the boat bottom for every 12 away from the transom. 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. For boats equipped with a bracket, calculate the same measurement but based on the bracket and not the transom. You also might not be able to lift the outboard out of the water entirely for storage. If your outboard motor height. What is the Virtual Sundance Film Festival? Step 4. But in many cases, its a little more complicated than that alone. s.setAttribute("src", script); Raising an outboard higher on the transom can reduce drag and raise top speed. The lowest point will likely be directly under your drain plug if youve got one. This measurement was approximately 4". }, 100); 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. Some fishing boats can handle the motor being underwater. Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. You also have the option to opt-out of these cookies. He is also a certified marine technician and the author of a popular text on writing local history. This is simply a measurement taken from the top of the transom (top of What Kind of Fuel Does Your Marine Engine Need? It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. You need JavaScript enabled to view it. The outboard comes with mounting holes and brackets. Anything bigger than that your obviously going to need an extra long shaft. On the downside, a higher mount can interfere with the boaters steering capabilities. These are vertically aligned so the boater can make adjustments. The transom is the flat vertical section at the rear of the boat. It will ensure that the outboards trim will be effective, and it will save you gas too. disregard the downward pointing "hooks" at the front of the Youll need a short shaft outboard if its 15 or less than an inch shorter. Some fishing boats can handle the motor being underwater. function gtag(){dataLayer.push(arguments);} This measurement is primarily designed for single motor propulsion. Necessary cookies are absolutely essential for the website to function properly. This email address is being protected from spambots. Amazon has plate extensions to allow adjustments without buying a new motor: T-H Marine Jack Plate Extension. Boats that use longer outboard shafts include: Bass boats, ski boats, or center cockpit vessels will want to double-check their measurements to get it just right. A yardstick will help you determine if your outboard engine is at the right height. var interval = setInterval(function () { With some boats I have a pretty good idea as to what length motor should be hung on them. And the rule of thumb is that you should keep the cavitation plate level with the bottom or keel of the boat. 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. Beginning boaters should be aware of the boats measurements. To break it down a bit more for you: Short shafts are 15-inches long. In lower mounting, the engine is set lower than the recommended standard. If measuring an existing outboard: Measure from the inside top of mounting bracket down to anti-cavitation plate above propeller (this is the largest plate/fin directly above the propeller). If the propeller fails to ventilate, the motor is mounted to low. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; 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. Step 2 requires the propeller's radius (check the user manual and then the technical drawing). storeDisplayName: "Marine Parts Warehouse", I would ask you to go back and measure the transom of your boat. 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? Or it can have an angle degree as high as 30. Measure from the top of the transom to the bottom of the hull. This, however, is not recommended for the beginning boater. var path = 'hr' + 'ef' + '='; since 1986. This could also effect your travelling capabilities on the boat trailer. up to the bottom of the motor brackets, (as in #1). Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. In addition, motor totes will not harm the finish of the lower unit. This provides seaworthiness and offers maximum protection from large seas. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. Which Navigation Lights Does Your Boat Need? Recommended Engine Oil 2-Stroke Outboard Motor Oil. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc.

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