It varies between different motors and boats. And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. Ill also explain the difference between short and long shafts and how they vary by type of boat. You Copyright 2017 Dealer Spike All Rights Reserved. stream 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. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. It can also improve the experience of driving a faster boat. For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. In the photo above, we've measured from the motor bracket to the top of 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. Higher mounting decisions should be left to the professionals. It is where the outboard is mounted, and some boat owners place the name of the boat. 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. xmlHttp.open('POST', 'https://bes.gcp.data.bigcommerce.com/nobot'); Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. 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. 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. (Putting a 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. Repowering your boat is one of the most expensive upgrades you can make. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. Other boats that need extra long shafts are: Read my other articles on outboard motors. This email address is being protected from spambots. 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. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. Many boat transoms are modified to use a different length of outboard by using a bracket. (We wont go into name-calling here, but the actual term for the cavitation plate is an anti-ventilation plate.) s = d.createElement("link"); disregard the downward pointing "hooks" at the front of the Here we look at the effects of standard, lower and higher mounting. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. 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). For slower boats, its less critical to. These are vertically aligned so the boater can make adjustments. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. Outboard motors can be fitted to a variety of boats, so manufacturers have standardized their engines to go on virtually anything. 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. If your outboard motor height. Another important measurement is the transom angle. Follow Westshore Marine & Leisure on Wordpress! Long shafts are 20-inches long. Other factors to consider when determining the mounting height of an outboard are related to performance. 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. 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. var interval = setInterval(function () { 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. Or it can have an angle degree as high as 30. Some may call it a standard length while others may call it a short or a long shaft. d.addEventListener("DOMContentLoaded", function (e) { In lower mounting, the engine is set lower than the recommended standard. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. Again, make sure that you are measuring to the flat part of the brackets; My family and I used it to fish, ski (yes, you can ski behind a pontoon boat), and cruise the lakes near our home. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal. Beginning boaters should be aware of the boats measurements. The pros and cons of properly . Chances are the boat was designed with a specific size of outboard in mind. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. This will keep the prop in the water when the boat pitches in waves, or hobby-horses. Small portable outboards ranging from 2 to 20 horsepower are usually sold only in short or long shaft versions. resting on the transom if you had the motor all the way down on the boat Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. Eq*^?6R83e+j}UY.(M7k]~4g)g ~wmS{ O7t/o(W|X? Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. This distance is very important to the performance of you boat. The cookies is used to store the user consent for the cookies in the category "Necessary". Save my name, email, and website in this browser for the next time I comment. Happy boating! ), Al Shields With some boats I have a pretty good idea as to what length motor should be hung on them. (127 mm). A long shaft engine requires a height of 20 and extra-long shaft engines will need a transom height of 25. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. Most transom savers can support up to a 150HP motor, which is sufficient for most regular boats. height (that I'm aware of); probably the most common is: As mentioned above, the operation of the propeller relies on the transom height. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. out the confusion. I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. A: The short answer is Yes. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. Your email address will not be published. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. Measure from there down to the top of the cavitation plate, also known as the anti-ventilation plate. However, the motor should not be raised more than 5 inches above the standard position. What Kind of Fuel Does Your Marine Engine Need? But, how do you measure it? 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. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. Doing this can have adverse effects. August 9/08). s.setAttribute("src", script); If you have a question or need additional information,contact ustoday. I show you how to consistently measure your prop to pad height. xmlHttp.setRequestHeader('Content-Type', 'application/json'); The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The transom is the back of the boat where the motor is hung. On this type of boat, if you are in doubt, default to the longer-shafted outboard. 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? The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. Buying a boat can be an exciting purchase. var h = d.getElementsByTagName("head"), I mean it is better to be safe than sorry, am I right? Boats that use longer outboard shafts include: 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. Trimming in, trimming down, and trimming out are all terms that a beginning boater should learn. Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. displayMicroOffers: false, All things considered, sticking with the industry standard is best for the beginner. Follow Westshore Marine & Leisure on Twitter! Top 10 Choices for Boaters, Mercury Introduces 600HP V12 Verado Outboard Engine, The Outboard Expert: Tohatsu Propane Outboard Engine. Necessary cookies are absolutely essential for the website to function properly. straight edge on the top of the transom to "extend" it out Check out the full chart of the Mercury outboard model code and its features. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. 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. Finding the right size is a matter of looking at what youve got and taking out the measuring tape. It also cuts into speed and fuel efficiency. 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. In the second photo, we've measure down from the top of the Detwiler Before we get started lets see what a boat transom is and what it does. You must be still in the blue about that matter. I run a 9.9 Mercury Bigfoot 20" shaft off the swim platform of my 89 Trophy 2160. With the long side (22 1/2), place a carpenters square ) in opposition to the keel. As with anything, there are exceptions to the rule. Doing so, will put the propeller right below the boat. Look at the part of your motor that would be As mentioned above, the operation of the propeller relies on the transom height. 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. h[0].appendChild(s); All rights reserved. If you said something smaller than that, thats where it can get tricky. Knowing how this can affect the overall operation of the boat is a factor to be considered. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. 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. trimming the motor out by one-half to full trim. #2. These cookies will be stored in your browser only with your consent. This measurement would be the inches of Each one has a totally different effect on the boats performance. This measurement is primarily designed for single motor propulsion. Say the 20 shaft is a long shaft length for gas engines, but it is a short shaft length for electric outboard motors. Problems with getting the ventilation plate too low include slower hole-shot and lower top-end speeds. Youll need a short shaft outboard if its 15 or less than an inch shorter. How to Measure Transom Height For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. However, you will need an understanding of how the degrees will alter the boats usability. You will also risk hitting bottom or submerge objects more frequently such as rocks or logs. s = d.createElement("script"); If it measures between 17 and 22, you'll want to go with a long shaft motor. In addition, motor totes will not harm the finish of the lower unit. Most of the time, adding a hydrofoil to an outboard improves performance. (In the case of the faster There are a series of four to six holes at the top of the bracket, and the lower bolts actually fit into slots. One of the main concerns is causing the engine to overheat if not enough water reaches the engine to keep it cool. There are 2 steps to help get a relatively accurate figure. Some outboards have a serial number that tells you which shaft length to go for. The boat transom can be flat with zero degree angles. steel ruler, etc. A2: Instead of changing to the short outboard shaft, you can try the Jack Plate first. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. function loadScript(script) { This also means it can affect the safety of the boat. While this is the case there is certain saltwater motors that are extra extra long at 30. The outboard comes with mounting holes and brackets. s.setAttribute("type", "text/javascript"); var prefix = 'ma' + 'il' + 'to'; A big NO. You also might not be able to lift the outboard out of the water entirely for storage. %PDF-1.7 For vessels with transom-mounted outboards, you can easily figure out which type of outboard you need to get. 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. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. Many single-engine boats mount a smaller auxiliary motor for emergency use. Then open up the clamp bucket. With this in mind, how can I determine if my outboard has a short or long shaft? All things considered, sticking with the industry standard is best for the beginner. This is measured by the propeller shaft being parallel to the vessels bottom. 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. (Any measurement given as "off the transom" })(); ensure that your measurement is accurate. parallel with the straight edge. (function () { <> But opting out of some of these cookies may affect your browsing experience. 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). If you go too short your more than likely going to cavitate and loose power. Take the center measurement from the top to the bottom of the hull. The propellers will also have trouble reaching the water. PayTomorrow.mpeInit({ s.setAttribute("rel", "stylesheet"); 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. Make sure that you are measuring straight up, at a 90 degree angle to Why wont Touch ID be under the screen in the iPhone 15 and iPhone 16? See diagram below. 1 0 obj Measuring the shaft length can be done in various ways, but the most common way is by using a tape measure. 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. Some fishing boats can handle the motor being underwater. When the boattransom is too low, the motor could end up underwater. One of the great things about an outboard motor is how versatile it is. gtag('js', new Date()); Check the literature about your model boat online, and you may be surprised to find that the number is published for you. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. Buying a boat can be an exciting purchase. It does not store any personal data. Smaller inflatables and dinghies needshort shaft motors, whilst bigger boats require long or, in some circumstances, extreme long shaft versions. The brackets can add 1 inch to the overall mounting height of the outboard. boats.com, 1221 Brickell Avenue, 23rd Floor, Miami, FL 33131, USA. Its important to note that manufacturers call their models different things. straight edge from the center of the pad, but this time you're measuring The propellers will also have trouble reaching the water. The average transom angle is around 14 degrees. Required fields are marked *. Then, you can pick the right engine. The transom is the flat vertical section at the rear of the boat. As with anything, there are exceptions to the rule. I would ask you to go back and measure the transom of your boat. would be more accurate.) You also have the option to opt-out of these cookies. As a yacht designer and boater, I prefer longer shafts. https://www.bornagainboating.com/Get Your Born Again Boating Clothing! The greater the number, the more the drive may sway (also called tuck under or negative trim). The vertical distance between the interior of the clamp and the cavitation plate is the shaft length specified by the outboard manufacturer. Place the rulers end on the ground behind the club and let the club to rest on top of it. Since the length of the shaft of your outboard is associated with the size boat, smaller engines will generally have shorter shafts. A deep Vee hull will result in a different measurement than a flatter . So how to measure outboard shaft length? To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. The same is true for the newest, high-powered offshore fishing boats, where triple or quadruple motor setups are becoming more and more common. Read the measurement on the transoms bottom. Picking the right shaft length is mostly a factor of the transom height or the back of the boat. This was the height of my 225 Yamaha on my TR21 On the downside, a higher mount can interfere with the boaters steering capabilities.