3 0 obj The motor length corresponds to the transom height of the boat, measured from the keel to gunwale at the transom. Boats that use longer outboard shafts include: What Kind of Fuel Does Your Marine Engine Need? 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 first step is to determine the height of your boat's transom. When the boattransom is too low, the motor could end up underwater. But, how do you measure it? If you have a question or need additional information. Any owner seeking the last bit of speed from an outboard-powered boat should grab a yard stick. The first order of business is to measure your boat for the ideal fit. center of the propshaft. 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. Copyright 1999-2023 Boats Group. Most of the time, adding a hydrofoil to an outboard improves performance. For over five years he has worked as a newspaper reporter and historic researcher. To do so, take a measurement from the very top to the very bottom of the transom in the precise center. of the "bullet" on your lower unit. It can also improve the experience of driving a faster boat. With it comes a lot of responsibility and new things to learn including boat maintenance and boat basics. Step 4. 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. your motor will be higher.) All boats are different, and the motor manufacturers produce a variety of standard lengths. endobj Small portable outboards ranging from 2 to 20 horsepower are usually sold only in short or long shaft versions. function gtag(){dataLayer.push(arguments);} As a result, the issue is whether my boat need a short shaft or long shaft motor. Figuring out how to measure motor height on a Take your time and understand your boat and your entire transom. Will Charpentier is a writer who specializes in boating and maritime subjects. <> from the transom. This, however, is not recommended for the beginning boater. By clicking Accept, you consent to the use of ALL the cookies. Other boats that need extra long shafts are: Read my other articles on outboard motors. To make the yard stick long enough to measure the length of all the clubs, tape the ruler to the top. s = d.createElement("script"); All rights reserved. But opting out of some of these cookies may affect your browsing experience. and I'll explain it better, (or point you to someone that can help. Other factors to consider when determining the mounting height of an outboard are related to performance. To achieve 35 mph with a 6 hp engine, the total weight is 135 lbs (boat motor fuel passengers). I would also recommend finding your maximum horsepower rating which is located on the yellow coast guard tag towards the back of your boat. Actual shaft length is 21.5" on those. It also includes attaching the right engine. If youre looking for a bracket that can handle motors of up to 10/15 horsepower, go no further. Outboard Motor Shaft Length: How do I measure? Measure from the top of the transom to the bottom of the hull. Engine Oil Mixing Ratio Fuel 50: Engine Oil 1. When you measure the width of the stern, mark the center with a grease pencil. In the case of a dinghy or johnboat, this point may be the top of the transom. MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. Smaller boats may use adjustable jack plates that can be changed to fit any outboard. There is a simple test to see if your outboard motor is set at the best height. With some boats I have a pretty good idea as to what length motor should be hung on them. (616) 364-0666, On all contiguous US part orders over $100. 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). As a dealer I don't really like hearing this because there is a chance it could go either way and you have to get it right. It was a 23-foot Crestliner Grand Cayman pontoon boat. Bass boats, ski boats, or center cockpit vessels will want to double-check their measurements to get it just right. Theyre also useful if the back of your boat has a non-standard measurement. (127 mm). If you are looking to repower, they may be able to offer some sage advice. Actually there is no designated letter for short shaft. What the relationship to the pontoons is, I couldn't say. If so, send me an What are Apple Podcasts Subscriptions and Channels? These allow the mounting of a standard length outboard behind the transom. The average transom angle is around 14 degrees. Having the cavitation plate too low will cause excess drag and reduced performance at high speeds. As summer approaches there will be more boaters taking to the water. Why Rebounding Is A Key Skill for Fouth Players To Learn, Tips For Attacking a Zone Defense as a Youth Basketball Team, Why This is a Big Deal for the Sports Betting Industry. You can use a longer shaft than recommended and your boat will work fine. https:/. However, the shaft length for smaller boats could be long or short depending on its style, speed requirement, etc. Boat Transom Heights The Beginners Guide, Buying a boat can be an exciting purchase. This measurement was approximately 4". Mounting the outboard a little bit lower than the standard point could avoid the possible ventilation and slip on acceleration. It doesnt matter if you have a fiberglass boat, bay boat, big or small boat. If you have a small boat with a 15 to 17 inch aft transom, youll most likely need a short shaft outboard. 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 adjust the motor in a higher hole with a flat head screwdriver. It is unsafe to have the engine block too close to the water on a low transom. With such an important, long-term, and expensive upgrade, its never a bad idea to double-check. A: Any boat that has a 21 to 27 inch aft transom will need an extra long shaft outboard. % As mentioned above, the operation of the propeller relies on the transom height. The prop will be in cleaner, harder water as it advances farther aft, making it more efficient. What is the Virtual Sundance Film Festival? 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). 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. Like Westshore Marine & Leisure on Facebook! function mpeInit() { <> See When St. Peters Basketball Games Are Today! Of course, its always best to go with standard practices when choosing thebest boat engine. Before we start measuring the outboard shaft length, lets get it clear about whats referring to when we talk about the outboard shaft length. 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. Save my name, email, and website in this browser for the next time I comment. A reverse transom that sits too high can impact the propellers of the motor and motor bracket. Attention: Remember to measure the outboard shaft length straight up and down instead of measuring along the transom. If you decide to make adjustments, please consult a marine engine dealer about the boatdesign. Pad to bottom of There are 2 steps to help get a relatively accurate figure. The mounting height of an outboard motor can impact the speed and handling characteristics of the boat. Cutting the transom down is the only legal method to utilize a short shaft engine on a tall transom. Increased RPM and additional horsepower feed the need for speed. (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. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. The center is the point where your outboard motor is (ideally) located. What's the best height for my boat motor? This alone can outweigh the negatives when deciding to adjust the mount upwards. 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. Its where the outboard motor is attached, and its also where some boat owners put the boats name. 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. Knowing the width, height and depth of your transom allows you to make several important decisions when selecting or purchasing a new outboard. var path = 'hr' + 'ef' + '='; The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. enableMoreInfoLink: true, The correct shaft length for your boat depends on a few factors. s.setAttribute("rel", "stylesheet"); These are vertically aligned so the boater can make adjustments. Knowing how this can affect the overall operation of the boat is a factor to be considered. Boat transomangles play a pivotal role in the flexibility of the boats trimming abilities. However, there may be times when a boater strays away from these recommendations. Your goal is to measure how the outboard will sit, so start from the clamping plate and follow the centerline of the hull. Doing this can have adverse effects. Since the ventilation plate & foil are burried under water it is obviously too low. Simply start with the engine in idle, followed by trimming the motor out by one-half to full trim. Place the point of a yardstick at the middle of the top of the boat transom. The height is approximately six inches higher than with a propeller. Mounting the motor lower on the boat transomcan createexcessive spray, increase case drag, reduce underwater clearance, and negatively impact faster boats. He is a With a jack plate, you can mount it exactly where you want it. Boat transom angles play a pivotal role in the flexibility of the boats trimming abilities. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. 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. How Transom Height Is Measured height (that I'm aware of); probably the most common is: Pretty easy to figure out but like I said its crucial to pairing a motor with a boat. You mpeSelector: ".pt-mpe", 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. You must be still in the blue about that matter. | Sitemap, The Marine Parts Warehouse Outboard Museum, OBR Powerhead / Shortblock Warranty Claim Form, Remanufactured vs. actually have the propshaft above the pad.). Gear Oil Quantity 195ml(6.6 Fl.oz.) publicId: "32bf3437d1346295e03ebcf545f9c839", However, youll notice a little increase in drag and a decrease in top-end performance.