Offshore vessels are often equipped with a large mounting bracket so that the transom can be left at full height. The collapsing bubbles are loaded with extremely low-pressure water vapor, which causes damage to a variety of surfaces as they collapse. You may wonder how deep your prop should be in the water. So how to measure outboard shaft length? The transom is the boats flat vertical part at the back. If it measures 15" or with in a inch of that you will need a short shaft outboard. Is my outboard long or short shaft? Copyright 1999-2023 Boats Group. 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. I live for the weekends when I can go out on the water and escape the stress of life on land. To do so, you will want to measure at the exact center of the transom from the very top to the very bottom. And the rule of thumb is that you should keep the cavitation plate level with the bottom or keel of the boat. To break it down a bit more for you: Short shafts are 15-inches long. Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. To achieve this, the motor itself has to be attached at the correct height. 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. and I'll explain it better, (or point you to someone that can help. In the past, though, it housed the officers and captain of 17th, 18th and 19th century sailing ships. It is possible that the motor could hang low while transporting on the boat trailer causing future boat repairs. Over time, Boating Hub has grown into a resource for boating enthusiasts around world. If it measures between 17 and 22, you'll want to go with a long shaft motor. 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. 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. Be sure to measure carefully and research thoroughly before diving in. Beefier jack plates can be fitted should a boater be looking to mount an outboard with a shorter shaft than their transom demands. Remember, if you use a longer outboard shaft than you need you will be increasing your draft. %
mpeSelector: ".pt-mpe", 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. 7. Now that you have a better understanding of boat transom heights its time to take out the ruler and get the perfect measurements. When the boattransom is too low, the motor could end up underwater. There are instances where a lower mount may be okay. The pressure behind your hand dropped as you slid your hand back and forth through the water. Step 2: Three Variables to Consider Then open up the clamp bucket. Some outboards have a serial number that tells you which shaft length to go for. (1) Multiply the overall length of your boat (in feet) by it's widest beam at the stern (excluding any Fins and or Shear) (2) Locate that value on the left hand vertical column of the chart below.
How To Measure Outboard Motor Shaft Length [Long v Short] - Boating Hub For really big boats, the biggest and baddest six- or eight-cylinder outboards can have extra-extra long shafts up to 30 inches. would be more accurate.) I show you how to consistently measure your prop to pad height.
displayPrimeOffers: true, 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). When trimming your motor, they provide you a greater bow response. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. Using your existing control box and gauges will save you quite a bit of money in the end. loadScript(ptScript); The height of the boat transom dictates the size of the outboard motor. var path = 'hr' + 'ef' + '='; With the long side (22 1/2), place a carpenters square ) in opposition to the keel. Also, the boat will be more likely to hit bottom or submerge objects such as rocks or logs. In the case of a larger offshore boat, it may be to the top of a cutout on the . Cavitation is when the propeller is out of the water due to the boat forming a wake of "air bubbles" or "vapor cavities" around the prop. With this in mind, how can I determine if my outboard has a short or long shaft? Check out the Westshore Marine & Leisure google plus page! <>
Mounting the motor lower on the boat transom can create excessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. The transom is the flat vertical section at the rear of the boat. 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. It can also improve the experience of driving a faster boat. Plus, a low transom cut is an invitation for the water to flood the boat. It also includes attaching the right engine. Among them will be first-timers or those who have recently purchased their boats. 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.
Hold the tape on the top, center of the taffrail and measure straight down to the point, usually a sharp angle, where the transom joins the bottom of the boat. The correct shaft length for your boat depends on a few factors. 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. Here we look at the effects of standard, lower and higher mounting. 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. Other factors to consider when determining the mounting height of an outboard are related to performance. Safely but briskly accelerate. Ten years ago I bought my first boat. Commonly, the transom angle ranges from 0-30 degrees, with the average transom angle set at 14 degrees. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. bracket. of the motor off the transom
Workboats, sailboats, and displacement-hulled boats fall into this category. Although the longer outboard shaft length can lead to lower speed and more drag, the boat can push a heavier load. This is probably the worst case scenario out of the two. not sure that it's still used. Because of the increased friction, cavitation reduces efficiency. The rearmost structural member of your boat, it not only distributes the stress of the hull generated by the bow's impact as it cleaves the water, it's the place you hang your outboard motor. When mounting the engine, you want the cavitation plate to be 1 above the boat bottom for every 12 away from the transom. Boat hulls are designed in three basic types that range from slow displacement and semi-displacement hulls to the fastest planing hulls. 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. 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. Owners of bass boats, RIBs, or offshore fishing boats need to get this right. A: The short answer is Yes. 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. How can you figure out what your transom angle is? In lower mounting, the engine is set lower than the recommended standard. The brackets can add 1 inch to the overall mounting height of the outboard.
Boost Speed with Outboard Engine Height Adjustments Most of the time, adding a hydrofoil to an outboard improves performance. But in many cases, its a little more complicated than that alone. This provides seaworthiness and offers maximum protection from large seas. Thats a fairly simple list of symptoms, but if your motor is too low, youll probably notice at least one of them. maxAmount: 6500.0, a Detwiler manual jackplate. With it comes a lot of responsibility and new things to learn includingboat maintenanceand boat basics. (Any measurement given as "off the transom"
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. In the case of a dinghy or johnboat, this point may be the top of the transom. A reversetransom that sits too high can impact the propellers of the motor and motor bracket. https:/. Keep these numbers in mind if you ever have a need for a new outboard motor for your boat. (127 mm). endobj
The boat transom can be flat with zero degree angles. Long shafts are 20-inches long. All things considered, sticking with the industry standard is best for the beginner. 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. Always weigh the risks of making adjustments. For over five years he has worked as a newspaper reporter and historic researcher. C Cheaptoon Cadet Joined Aug 4, 2010 Messages 28 Aug 24, 2010 #4 Re: Motor height on pontoon? Your at your local outboard dealer shopping for a new motor and the salesman hits you with the question, "short or long shaft?". He is a
Outboard Motor Shaft Length & HP to Boat Calculating This exhaust port should be about 1 inch above the water line when the boat is idling. This measurement would be the inches of
I would ask you to go back and measure the transom of your boat. Rebuilt - What You Need to Know, Lower Unit and Sterndrive Break-In Instructions. motor brackets
To measure the transom height, measure from the center on for transom (rear of the boat). resting on the transom if you had the motor all the way down on the boat
They keep water out of your prop and increase water pressure in the system. Remanufactured 4 Cylinder 4-Stroke Cylinder Heads, Remanufactured 6 Cylinder 4-Stroke Cylinder Heads, Trim Relays, Trim Solenoids & Sending Units, Remanufactured V6 & V8 4-Stroke Cylinder Heads, Volvo Cobra SX Bearings and Bearing Carriers, Volvo Cobra SX Driveshaft, U-Joints & Parts, Volvo Cobra SX Transom Assembly & Bellows. This measurement was approximately 4". out the confusion. This cookie is set by GDPR Cookie Consent plugin. You
Another important measurement is the transom angle. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. displayMicroOffers: false, The general guideline for longer shaft outboards is that the transom height should be at least 20 inches (50,8cm) above the waterline.
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^zv_ cT,E1K/rAB54| 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.
However, you will need an understanding of how the degrees will alter the boats usability. No one wants to have issues with a new transom or boat repairs. The motor is what powers the boat so the two go hand-in-hand. As summer approaches there will be more boaters taking to the water. And thats usually the case since the electric outboards are designed with larger and more efficient propeller that needs longer shaft. The Effects of Standard, Lower and Higher Mounting. Lastly, knowing the year of your motor and what style of controls you have (side mount, concealed side mount, or binnacle) is also a plus because it will tell the dealer if your current controls are compatible with the motor you are purchasing.
Beginning boaters should be aware of the boats measurements. 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. For most boaters this is a no brainer, but for the novice or inexperienced boater it may be a tougher question. 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. This measurement is primarily designed for single motor propulsion. He is also a certified marine technician and the author of a popular text on writing local history. The cavitation plate is the horizontal surface of the lower unit immediately above the propeller. See diagram below. The clamp bracket is designed so that the engine's mounting height on the transom can be adjusted higher than standard. Take a long straight edge, (long carpenter's level or long
How-To: Pick A Great Portable Outboard Motor (2023 Guide) Shaft lengths are available in increments of 5. 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. You also might not be able to lift the outboard out of the water entirely for storage.
Transom Outboard Engine Position - YouTube There Look at the part of your motor that would be
How high exactly do you have to raise the transom?-. You'll need a short shaft outboard if it's 15 or less than an inch shorter. If your outboard motor height. (In the case of the faster
Each one has a totally different effect on the boats performance. Youll also want to pay attention when youre in shallow water because your prop will be lower than normal.
help with shaft length for a kicker - iboats Boating Forums 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. If it measures between 17 and 22, youll want to go with a long shaft motor. Basically, there are three main ways to measure motor
Measure from the top of the transom to the bottom of the hull. 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. There is a simple test to see if your outboard motor is set at the best height. While this is the case there is certain saltwater motors that are extra extra long at 30 and 35 shaft. Whether you already own a boat or looking for your first watercraft we are here to service your needs. Or it can have an angle degree as high as 30. How do you measure a transom on an outboard motor? No one wants to have issues with a new transom or boat repairs. Oftentimes you will want to adjust the outboard shaft length in order to improve the boat performance such as speed. The average transom angle is around 14 degrees. Generally, short shaft outboards are 15 inches, long shaft outboards are 20 inches, and extra-long outboards are 25 inches. trimming the motor out by one-half to full trim. var h = d.getElementsByTagName("head"), If your boat is newer and the manufacturer is still in business, you might also want to try to give them a call. It is unsafe to have the engine block too close to the water on a low transom. (function (d) { Here we will guide you in how to get the right boat transom height. This, however, is not recommended for the beginning boater. 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? Gear case sits just below or at the hull depth due to the deep v.
What Is a Transom? Where Onboard a Boat is It Located? Mounting the outboard motor in accordance with the industry standards is important. I also love helping others, which is why I created this website. Generally, the anti-ventilation plate on most engines is aligned with the bottom of the vessel. Whats the best height for my boat motor? When fighting waves from the stern, a 20-inch transom is considerably safer. The boater must also consider if the boat transom support is designed to bear the weight of a higher mount. (function () { But opting out of some of these cookies may affect your browsing experience. Actual shaft length is 21.5" on those.
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. The point where these measurements intersect is your centerline. Or it can have an angle degree as high as 30. This is the dimension you'll need when selecting a width for your outboard motor's mounting bracket. If the height of the boat transom is off it can cause major issues. Read the measurement on the transoms bottom. With some boats I have a pretty good idea as to what length motor should be hung on them. The distance between the ends of a transom is measured in inches.
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