how to measure transom height for outboard motor

Owners of bass boats, RIBs, or offshore fishing boats need to get this right. 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. 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). Before we get started lets see what a boat transom is and what it does. Increased RPM and additional horsepower feed the need for speed. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. 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. }) } }); })(document); Simply start with the engine in idle, followed by trimming the motor out by one-half to full trim. This cookie is set by GDPR Cookie Consent plugin. Check out the Westshore Marine & Leisure Youtube page! 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. If the propeller fails to ventilate, the motor is mounted to low. Also, how do you determine the length of an outboard transom? What types of boat need an extra long shaft? This was the height of my 225 Yamaha on my TR21 Tightening Torque for Engine. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. Measure from the top of the transom to the bottom of the hull. 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. There are instances where a lower mount may be okay. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. out the confusion. This restriction includes most fishing boats and longer sailboats. How the outboard will sit on the back of the boat depends on how the transom is designed. The height of the boat transom dictates the size of the outboard motor. var h = d.getElementsByTagName("head"), 1855 Alpine Avenue NWGrand Rapids, MI 49504This email address is being protected from spambots. The faster your boat, the more critical it is to get the sizing just right. The performance of these boats depends on quite a lot of factors, but getting the outboard length just right is an essential first step. This provides seaworthiness and offers maximum protection from large seas. I mean, who wants to purchase something as expensive as an outboard to only realize you bought the wrong one. 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. It is where the outboard is mounted, and some boat owners place the name of the boat. Doing this can have adverse effects. My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. You dont have to be a mathematician to determine the correct boat transomangle. storeDisplayName: "Marine Parts Warehouse", To achieve this, the motor itself has to be attached at the correct height. Here we look at the effects of standard, lower and higher mounting. Measure the area of the transom directly where the engine will be mounted. For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. Assistant Measuring tape Grease pencil 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. window.dataLayer = window.dataLayer || []; Learn More About Your Boats Systems By Joining The Born Again Boating Academy! I would ask you to go back and measure the transom of your boat. You need JavaScript enabled to view it. 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. For over five years he has worked as a newspaper reporter and historic researcher. #3. However, your boat will have slightly more drag which will reduce your maximum speed. If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. } At least if its too long you can raise the motor or "build up" your transom. Place the clubs bottom on the ground as though it were going to be used to strike a golf ball. primeApr: 12.99, 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. Triton. since 1986. Then open up the clamp bucket. This website uses cookies to improve your experience while you navigate through the website. Gear Oil Quantity 195ml(6.6 Fl.oz.) Save my name, email, and website in this browser for the next time I comment. AztH ^zv_ cT,E1K/rAB54| Add the two measurements and you get 6 1/2". If it measures anywhere from 17" to around 22", then your going to want to go with a long shaft motor. 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. (Putting a e-mail Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. Wherever the outboard clamping bracket is, use this as the basis for measurement. Some boats are equipped with transom-hung outboards while others have a bracket. A deep Vee hull will result in a different measurement than a flatter . It also cuts into speed and fuel efficiency. All boats are different, and the motor manufacturers produce a variety of standard lengths. No one wants to have issues with a new transom or boat repairs. To break it down a bit more for you: Short shafts are 15-inches long. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.2 841.8] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Basically, there are three main ways to measure motor If it measures between 17 and 22, you'll want to go with a long shaft motor. on How to Measure Outboard Shaft Length: The Only Guide You Need, ePropulsion vs Torqeedo: An All-Round Comparison, 55 lb Thrust Trolling Motors: All You Need to Know Before Purchase, Spot Lock Trolling Motor: Is It Worth It & Best Options in 2022, Wiring 24V Trolling Motors: 24 Volt Wiring Diagram (with Video), LiFePO4 Battery: Why Lithium iron Phosphate Batteries Are Your Best Options in 2022, Minn Kota vs MotorGuide: Best Option in 2022. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. What is the Virtual Sundance Film Festival? What is Transom Height? #2. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. These allow the mounting of a standard length outboard behind the transom. If you are looking to repower, they may be able to offer some sage advice. Use the mounting bracket on the motor to know where it will sit on the boat. xmlHttp.setRequestHeader('Content-Type', 'application/json'); 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. According to MarinePartsMan.com, the outboard can be raised 1 inch above the standard height for every 10 miles per hour of speed the boat can attain. What the relationship to the pontoons is, I couldn't say. ensure that your measurement is accurate. addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = addyd53b59933f6c3f2e8b59f1b4a6d41fa5 + 'vanssports' + '.' + 'com'; If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. debugMode: false, It is very versatile as it generally . For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. Which Navigation Lights Does Your Boat Need? Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. An inch or two probably wont make a big difference, but any more than that will lead to trouble. 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. (127 mm). The engine must be linked to the transom at the proper height for a propeller to best meet specific boating demands. 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. 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. What are Apple Podcasts Subscriptions and Channels? Boaters who consider going with a higher mount can see increased speeds. motor brackets Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. This is a measurement that has been used for BassCats, I'm The correct shaft length for your boat depends on a few factors. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. But in many cases, its a little more complicated than that alone. Always weigh the risks of making adjustments. Add yours in the comment and Ill get back to you asap. If your boats transom height is 15-16, a short shaft engine is required, and if it is 20-21, a long shaft engine is required. This could also affect your travelling capabilities on the boat trailer. Re: Dinghy with a long shaft motor? h[0].appendChild(s); Its important to note that manufacturers call their models different things. the propshaft below or above the pad. Among them will be first-timers or those who have recently purchased their boats. Step 3: Add another 10 cm (4'') to the previous calculation for the final ideal shaft length. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. The transom is the flat vertical section at the rear of the boat. Whether your on a pontoon boat, fishing boat, or speedboat boating is always one of the best times you can have. With a jack plate, you can mount it exactly where you want it. Actual shaft length is 21.5" on those. 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. actually have the propshaft above the pad.). Engine Oil Type Genuine or Recommended 2str Engine Oil. Tilt your motor until the bullet of the gearcase is <> Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. 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. Cavitation plates are used on the bottom components of boats to help them operate better. In the photo above, we've measured from the motor bracket to the top of 7. Is my outboard long or short shaft? <> 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? As mentioned above, the operation of the propeller relies on the transom height. This alone can outweigh the negatives when deciding to adjust the mount upwards. If you decide to make adjustments, please consult a marine engine dealer about the boat design. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. You can use a longer shaft than recommended and your boat will work fine. Then finally test your outboard, if the mount is perfect. 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. The vertical distance between the interior of the clamp and the cavitation plate is the shaft length specified by the outboard manufacturer. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. 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. Two years ago, I bought a Boston Whaler to fish off the coast. On the downside, a higher mount can interfere with the boaters steering capabilities. When trimming your motor, they provide you a greater bow response. If you go too short your more than likely going to cavitate and loose power. These cookies track visitors across websites and collect information to provide customized ads. Having the cavitation plate a bit lower than the transom is preferable to having it too high. If you have a jackplate, you may have to get a bit creative in your All rights reserved. Among them will be first-timers or those who have recently purchased their boats. 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. The transom is the boats flat vertical part at the back. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Beginning boaters should be aware of the boats measurements. Some outboards have a serial number that tells you which shaft length to go for. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel.

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