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. |. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. You must be still in the blue about that matter. The height is approximately six inches higher than with a propeller. Beginning boaters should be aware of the boats measurements. brackets. The transom is the flat vertical section at the rear of the boat. How can you figure out what your transom angle is? All boats are different, and the motor manufacturers produce a variety of standard lengths. 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. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. You will also risk hitting bottom or submerge objects more frequently such as rocks or logs. You need JavaScript enabled to view it. With a jack plate, you can mount it exactly where you want it. It also cuts into speed and fuel efficiency. Doing this can have adverse effects. 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). This alone can outweigh the negatives when deciding to adjust the mount upwards. The shaft length for outboard motors has nothing to do with the water line. 12 Small Fishing Boat Accessories to Buy Today. As summer approaches there will be more boaters taking to the water. Some outboards have a serial number that tells you which shaft length to go for. You'll need a short shaft outboard if it's 15 or less than an inch shorter. This illustration depicts four different outboard mounting height options (courtesy Mercury Marine). Bass boats, ski boats, or center cockpit vessels will want to double-check their measurements to get it just right. When you measure the width of the stern, mark the center with a grease pencil. 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 break it down a bit more for you: Short shafts are 15-inches long. Required fields are marked *. Small motors built for sailboats might come in a unique configuration with an extremely long shaft since these are mounted higher off the water. 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. Cavitation plates are used on the bottom components of boats to help them operate better. 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}'); Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. This restriction includes most fishing boats and longer sailboats. You may wonder how deep your prop should be in the water. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. These two measurements will give you the length of the shaft you need. 4 0 obj Many boat transoms are modified to use a different length of outboard by using a bracket. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. (function () { 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. function loadScript(script) { Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. Read the measurement on the transoms bottom. 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. 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. This is measured by the propeller shaft being parallel to the vessels bottom. Again, make sure that you are measuring to the flat part of the brackets; Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. No one wants to have issues with a new transom or boat repairs. This would not be a good thing. The motor is what powers the boat so the two go hand-in-hand. Or it can have an angle degree as high as 30. https:/. Add yours in the comment and Ill get back to you asap. Simply start with the engine in idle, followed bytrimming the motor out by one-half to full trim. This measurement was approximately 4". Later in the article is an image that shows you exactly where to measure. Other boats that need long shafts are. The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. So from there, I will try to help out by asking questions about your boat such as what type it is and the length. Copyright 1999-2023 Boats Group. If it measures between 17 and 22, you'll want to go with a long shaft motor. These cookies ensure basic functionalities and security features of the website, anonymously. For over five years he has worked as a newspaper reporter and historic researcher. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. Youll need a short shaft outboard if its 15 or less than an inch shorter. However, your boat will have slightly more drag which will reduce your maximum speed. Although the longer outboard shaft length can lead to lower speed and more drag, the boat can push a heavier load. These are vertically aligned so the boater can make adjustments. It is extremely important that the boater understands the significance of the transoms height. These are vertically aligned so the boater can make adjustments. Here we will guide you in how to get the right boat transom height. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. This is a measurement that has been used for BassCats, I'm 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. var xmlHttp = new XMLHttpRequest(); Necessary cookies are absolutely essential for the website to function properly. Check the literature about your model boat online, and you may be surprised to find that the number is published for you. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; Actually there is no designated letter for short shaft. former editor at Boating Magazine and contributor to many national publications minAmount: 300.0, Your email address will not be published. ensure that your measurement is accurate. the aluminum plate on top of the transom), to the bottom of the motor The transom is the boats flat vertical part at the back. 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. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. Well, raising the outboard motor can be an easy task for you. storeDisplayName: "Marine Parts Warehouse", Using your existing control box and gauges will save you quite a bit of money in the end. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. 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. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. mpeSelector: ".pt-mpe", All things considered, sticking with the industry standard is best for the beginner. How do you measure a transom on an outboard motor? } If you have already measured you transom tip to bottom to be 20", then if you place aux sdieways to central engine your available transom height will be probably 1"-1.5" " higher and work perfecty. xmlHttp.setRequestHeader('Content-Type', 'application/json'); 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. Be sure to measure carefully and research thoroughly before diving in. This measurement would be the inches of The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. To measure the transom height, measure from the center on for transom (rear of the boat). 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. This measurement is primarily designed for single motor propulsion. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. He is a 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 you go too short your more than likely going to cavitate and loose power. A big NO. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. Owners of bass boats, RIBs, or offshore fishing boats need to get this right. var prefix = 'ma' + 'il' + 'to'; 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. Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? Figuring out how to measure motor height on a This distance is very important to the performance of you boat. 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 height of the boat transom dictates the size of the outboard motor. Whats the best height for my boat 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. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. <>/Metadata 127 0 R/ViewerPreferences 128 0 R>> xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); 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. Then finally test your outboard, if the mount is perfect. publicId: "32bf3437d1346295e03ebcf545f9c839", Step 2: Three Variables to Consider It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. The lowest point will likely be directly under your drain plug if youve got one. Step 4. The greater the number, the more the drive may sway (also called tuck under or negative trim). var addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@'; For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. Will Charpentier is a writer who specializes in boating and maritime subjects. Its important to note that manufacturers call their models different things. Is my outboard long or short shaft? var h = d.getElementsByTagName("head"), In lower mounting, the engine is set lower than the recommended standard. When mounting the engine, you want the cavitation plate to be 1 above the boat bottom for every 12 away from the transom. While this is the case there is certain saltwater motors that are extra extra long at 30. 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. 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. 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. If you have a jackplate, you may have to get a bit creative in your This is simply a measurement taken from the top of the transom (top of I believe 20 to 21 inches is the optimum length for a lengthy shaft. Repowering your boat is one of the most expensive upgrades you can make. Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. In the case of a dinghy or johnboat, this point may be the top of the transom. However, the motor should not be raised more than 5 inches above the standard position. The pros and cons of properly . The propellers will also have trouble reaching the water. This is measured by the propeller shaft being parallel to the vessels bottom. To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). If the propeller fails to ventilate, the motor is mounted to low. Learn More About Your Boats Systems By Joining The Born Again Boating Academy! endobj Increased RPM and additional horsepower feed the need for speed. Over time, Boating Hub has grown into a resource for boating enthusiasts around world. As mentioned above, the operation of the propeller relies on the transom height. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. Whether you already own a boat or looking for your first watercraft we are here to service your needs. 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. 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. not sure that it's still used. Simply start with the engine in idle, followed by trimming the motor out by one-half to full trim. document.getElementById('cloakd53b59933f6c3f2e8b59f1b4a6d41fa5').innerHTML = ''; What are Apple Podcasts Subscriptions and Channels? } Simply start with the engine in idle, followed by, If you decide to make some custom adjustments we have the. This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. Propshaft in A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. As summer approaches there will be more boaters taking to the water. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. Some fishing boats can handle the motor being underwater. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. <> 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. They operate as a planing surface, allowing your boat to climb to the top more quickly. In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. This cookie is set by GDPR Cookie Consent plugin. Each one has a totally different effect on the boats performance. Thats it. This also means it can affect the safety of the boat. Among them will be first-timers or those who have recently purchased their boats. So how to determine the outboard shaft length? What types of boat need an extra long shaft? Read the following to get the optimal shaft length for outboard motors! Because of the increased friction, cavitation reduces efficiency. I also love helping others, which is why I created this website. It is unsafe to have the engine block too close to the water on a low transom. It is where the outboard is mounted, and some boat owners place the name of the boat. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. :$I>M W$h"%U_yzIb?]NHg_G|r@nX eTf."SQ Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. Another important measurement is the transom angle. How Transom Height Is Measured I live for the weekends when I can go out on the water and escape the stress of life on land. ), Al Shields (Any measurement given as "off the transom" This could also affect your travelling capabilities on the boat trailer. Your email address will not be published. The transom angle is the vertical incline of the transom and is measured in degrees. If you are running a twin-engine setup, then measure the same distance from each clamping plate to the bottom of the hull. steel ruler, etc. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. Measure from the top of the transom to the bottom of the hull. He is also a certified marine technician and the author of a popular text on writing local history. "brackets". ), and place it on the bottom of the pad in the center. A yardstick will help you determine if your outboard engine is at the right height. Analytical cookies are used to understand how visitors interact with the website. You reply, "Im not sure, I think its a long". This alone can outweigh the negatives when deciding to adjust the mount upwards. 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. 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. MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. By clicking Accept, you consent to the use of ALL the cookies. 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. This was the height of my 225 Yamaha on my TR21 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. This will be the This could also effect your travelling capabilities on the boat trailer. Each one has a totally different effect on the boats performance. 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. Plus, a low transom cut is an invitation for the water to flood the boat. 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). An outboard motor can drive just about any sort of boat with proper mounting. Tightening Torque for Engine. The correct shaft length for your boat depends on a few factors. Boaters who consider going with a higher mount can see increased speeds. Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. 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. to where the brackets were actually resting on the transom. Here we look at the effects of standard, lower and higher mounting. It can also improve the experience of driving a faster boat. The cookie is used to store the user consent for the cookies in the category "Performance". Shaft lengths are available in increments of 5. 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. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. Other boats that need extra long shafts are: Read my other articles on outboard motors. The faster your boat, the more critical it is to get the sizing just right. If you are looking to repower, they may be able to offer some sage advice. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. (function (d) { This website uses cookies to improve your experience while you navigate through the website. Outboards designed for saltwater applications usually have longer shafts. When trimming your motor, they provide you a greater bow response. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. Re: Dinghy with a long shaft motor? of the motor off the transom Measure from the top of the straight edge to the center of the front If you said something smaller than that, thats where it can get tricky. Depending on the manufacturer, size names might change. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. Allowing the propeller to pull water from underneath and push it out behind the boat. However, the motor should not be raised more than 5 inches above the standard position. If you went too long it would still work but it may lack in performance. Raising an outboard higher on the transom can reduce drag and raise top speed. 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. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. Any questions? Pad to bottom of enableMoreInfoLink: true, Tilt your motor until the bullet of the gearcase is Selecting the Correct Size Outboard Shaft, What is the Best Outboard Motor for Saltwater, Diagnosing Common Outboard Motor Problems, Best Beginner Boats Everything You Need to Know. Not to measure boat speed, but to gauge the mounting height of the outboard motor on the boat transom. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. 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. bracket. straight edge from the center of the pad, but this time you're measuring Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. To achieve this, the motor itself has to be attached at the correct height. You also have the option to opt-out of these cookies. resting on the transom if you had the motor all the way down on the boat displayPrimeOffers: true, Save my name, email, and website in this browser for the next time I comment. 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. Determining Your Boat Transom Angle The transom angle - commonly measured in degrees - is the transom's vertical inclination. 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. But in many cases, its a little more complicated than that alone. The cookie is used to store the user consent for the cookies in the category "Analytics". As with anything, there are exceptions to the rule. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! 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. 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. 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. Buying a boat can be an exciting purchase. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. The transom is the "back wall" of your boat, the most rearward part of your hull. This cookie is set by GDPR Cookie Consent plugin. Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. Its where the outboard motor is attached, and its also where some boat owners put the boats name. Or it can have an angle degree as high as 30. It also decreases the boats lift and increases the time it takes for the boat to reach plane. #2. Typical motor lengths include the following. Make sure that you are measuring straight up, at a 90 degree angle to If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. This allows the engine to idle without the flow of the exhaust being restricted. 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. Place the rulers end on the ground behind the club and let the club to rest on top of it. Long shafts are 20-inches long. In the case of a larger offshore boat, it may be to the top of a cutout on the . Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. Any owner seeking the last bit of speed from an outboard-powered boat should grab a yard stick. Outboard shaft length plays a crucial role in the performance of your boat. 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. You dont have to be a mathematician to determine the correct boat transomangle. Check out the Westshore Marine & Leisure Youtube page! Triton. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. I would ask you to go back and measure the transom of your boat. In lower mounting, the engine is set lower than the recommended standard. It can also improve the experience of driving a faster boat. If you have a question or need additional information,contact ustoday. For most boaters this is a no brainer, but for the novice or inexperienced boater it may be a tougher question. 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). A deep Vee hull will result in a different measurement than a flatter . 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. out the confusion. Boats with more engine power and weight require longer shaft outboards for better balance.
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