Anything bigger than that your obviously going to need an extra long shaft. 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. Actually there is no designated letter for short shaft. if (PayTomorrow) { So how to measure outboard shaft length? 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. Owners of bass boats, RIBs, or offshore fishing boats need to get this right. Then adjust the motor in a higher hole with a flat head screwdriver. The faster your boat, the more critical it is to get the sizing just right. would be more accurate.) relation to pad The transom angle is the vertical incline of the transom and is measured in degrees. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. resting on the transom if you had the motor all the way down on the boat The transom is the boats flat vertical part at the back. The shaft length for outboard motors has nothing to do with the water line. } However, the motor should not be raised more than 5 inches above the standard position. Or it can have an angle degree as high as 30. The transom in a boat today is a place to hang your outboard motor. To achieve this, the motor itself has to be attached at the correct height. 7. function loadScript(script) { Some outboards have a serial number that tells you which shaft length to go for. parallel with the straight edge. In the photo above, we've measured from the motor bracket to the top of A yardstick will help you determine if your outboard engine is at the right height. What Kind of Fuel Does Your Marine Engine Need? Whether you already own a boat or looking for your first watercraft we are here to service your needs. Another important measurement is the transom angle. The boat transom height is measured from the lowest point on the keel along the center line to the spot where the outboard motor's mounting holes bracket rests. All things considered, sticking with the industry standard is best for the beginner. displayMicroOffers: false, It can also improve the experience of driving a faster boat. The transom is the flat vertical section at the rear of the boat. When the boat transom is too low, the motor could end up underwater. Plus, a low transom cut is an invitation for the water to flood the boat. 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? These allow the mounting of a standard length outboard behind the transom. 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. 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 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. However, there may be times when a boater strays away from these recommendations. This is also known as the shaft length. Recommended Engine Oil 2-Stroke Outboard Motor Oil. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. If you are looking to repower, they may be able to offer some sage advice. The point where these measurements intersect is your centerline. 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 pressure behind your hand dropped as you slid your hand back and forth through the water. When the boattransom is too low, the motor could end up underwater. 4 0 obj We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. If you are running a slower boat, the exact location of the ventilation plate is less important. Having the cavitation plate a bit lower than the transom is preferable to having it too high. Industry standards dictate that for short shaft engines the transom height should be 15. (In the case of the faster Remember, if you use a longer outboard shaft than you need you will be increasing your draft. Other boats that need extra long shafts are: Read my other articles on outboard motors. Before we get started lets see what a boat transom is and what it does. Measure from the top of the transom to the bottom of the hull. However, the motor should not be raised more than 5 inches above the standard position. On this type of boat, if you are in doubt, default to the longer-shafted outboard. straight edge on the top of the transom to "extend" it out The transom is the "back wall" of your boat, the most rearward part of your hull. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. Get the latest updates on new products and upcoming sales, 2023 Marine Parts Warehouse Incorporated Boaters who consider going with a higher mount can see increased speeds. How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. 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. 3 0 obj Ten years ago I bought my first boat. 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. 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. 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. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. }, 100); However, there may be times when a boater strays away from these recommendations. maxMicroAmount: 0.0, (616) 364-0666, On all contiguous US part orders over $100. So from there, I will try to help out by asking questions about your boat such as what type it is and the length. This placement is not only recommended but it will give you the best performance compared to something that is too long or too short. How the outboard will sit on the back of the boat depends on how the transom is designed. It is where the outboard is mounted, and some boat owners place the name of the boat. Copyright 1999-2023 Boats Group. A: The answer varies by boat, but here are some rules of thumb for matching a short shaft outboard to your boat. It is extremely important that the boater understands the significance of the transoms height. 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. var addyd53b59933f6c3f2e8b59f1b4a6d41fa5 = 'info' + '@'; This will keep the prop in the water when the boat pitches in waves, or hobby-horses. var xmlHttp = new XMLHttpRequest(); If the height of the boat transom is off it can cause major issues. Buying a boat can be an exciting purchase. It was a 23-foot Crestliner Grand Cayman pontoon boat. var path = 'hr' + 'ef' + '='; If the propeller fails to ventilate, the motor is mounted to low. A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. Its important to note that manufacturers call their models different things. Its still smart to measure it yourself though, just in case, the design changed over the years. boats.com is part of the Boats Group Network. } What Types of Documents Can be Sent to your Kindle Library? 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. s.setAttribute("rel", "stylesheet"); If you decide to make adjustments, please consult a marine engine dealer about the boat design. If you have a jackplate, you may have to get a bit creative in your 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. Then finally test your outboard, if the mount is perfect. The amount of degrees the transom leans back from vertical is known as the transom angle. It also includes attaching the right engine. Other factors to consider when determining the mounting height of an outboard are related to performance. Make sure that you are measuring straight up, at a 90 degree angle to Some boats are equipped with transom-hung outboards while others have a bracket. Again, make sure that you are measuring to the flat part of the brackets; You also have the option to opt-out of these cookies. 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. In step 3, add another 10 cm (4") to the previous calculation in order to develop the ideal shaft length. 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. The motor is what powers the boat so the two go hand-in-hand. This would not be a good thing. With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. There are also specialty motor shaft lengths. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. Beginning boaters should be aware of the boats measurements. former editor at Boating Magazine and contributor to many national publications The vertical distance between the interior of the clamp and the cavitation plate is the shaft length specified by the outboard manufacturer. publicId: "32bf3437d1346295e03ebcf545f9c839", Here we look at the effects of standard, lower and higher mounting. This is somewhat similar to #2, in that you are again measuring with a Height Measurement: Recommended Shaft Length: 14" - 17.25" 15" Shaft (Short) 17.25" - 19.5" Varies by application 19.5" - 22.5" Each one has a totally different effect on the boats performance. This will be the Beyond motorboats designed for large outboards, you will see outboards hanging on the sterns of everything from small canoes to large cruising sailboats. A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. However, your boat will have slightly more drag which will reduce your maximum speed. The outboard comes with mounting holes and brackets. See When St. Peters Basketball Games Are Today! To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). When mounting the engine, you want the cavitation plate to be 1 above the boat bottom for every 12 away from the transom. function gtag(){dataLayer.push(arguments);} 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. It also decreases the boats lift and increases the time it takes for the boat to reach plane. Two years ago, I bought a Boston Whaler to fish off the coast. Each one has a totally different effect on the boats performance. Safely but briskly accelerate. Among them will be first-timers or those who have recently purchased their boats. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". These cookies ensure basic functionalities and security features of the website, anonymously. Among them will be first-timers or those who have recently purchased their boats. brackets. 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. 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 achieve this, the motor itself has to be attached at the correct height. Typical motor lengths include the following. Increased RPM and additional horsepower feed the need for speed. % How Transom Height Is Measured Repowering your boat is one of the most expensive upgrades you can make. 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. var ptScript = "https://cdn.paytomorrow.com/js/pt-mpe.min.js"; With some boats I have a pretty good idea as to what length motor should be hung on them. Add the two measurements and you get 6 1/2". 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 motor is what powers the boat so the two go hand-in-hand.

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