what height should an outboard motor be set at
You … All rights reserved. We’ll think of a motor support as a solution that utilizes the outboard engine’s hydraulic trim and tilt system to facilitate support. The anti-ventilation plate is designed to prevent air from being sucked down the lower unit and into the propeller where it can cause loss of thrust. Outboard motors are engines mounted on the outside of the stern of the hull. Crashnrondo. Also to know is, what does a cavitation plate do on a mud motor? You should only change one thing at a time, so you know what each change does. A special case is an outboard on a bracket. Reproduction in whole or in part without permission is prohibited. There's a fuel tank (not shown) inside the case ofthe motor at the top, big enough to hold perhaps 23 liters (6 gallons) of gas. should not be tolerated, and should be eliminated to main-tain the life of your outboard. 43 mph with top stowed and just me on the boat! Itâs an Alumacraft tournament pro 170cs. However, it also has the disadvantage that it The Plate should be out of the water while on full plane. The bracket manufacturer will recommend the outboard height according to the bracket shape and length. Many products featured on this site were editorially chosen. ORIGINAL POST. Beginning boaters should be aware of the boat’s measurements. Mercury Marine Unveils Worldâs First V12 Outboard, Yamaha Debuts Updated V6 Offshore Outboards, Eeling with Planer Boards for Striped Bass, Light Tackle Thresher Shark Action in Southern California, Finding and Catching Trophy Tarpon in the Florida Keys. Copyright © 2021 Sport Fishing Magazine. 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. The standard installation of an outboard has the top of the transom of the boat at the same level as the bottom of the motor portion of the outboard. On some boats, the hull design will allow raising the motor a little to improve speed and economy. 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. MarinePartsMan.com also says that V6 bass-boat engines have a 20-inch shaft. The anti-ventilation plate – or cavitation plate on an outboard motor should be no more than about 25mm below the bottom of the hull centre. Note that we have not looked at the water line: our outboard prop depth is set in relationship to the hull bottom, not the waterline (power boats). Basically, there are three main ways to measure motor height (that I'm aware of); probably the most common is: You should not go above a 10 HP motor on a drift boat. 9 Just measure your transom and see what height it is. If you want extra speed you need a much more powerful motor but the type of motor that would increase the speed of your drift boat would make it almost impossible to steer and would therefore be useless in the long run. 2: The transom height needs to suit the outboard and ensure that the propeller will be in the correct depth ⦠5,484,311 has the advantage that it allows the outboard motor to be set to any selected height from a remote location by a closed-loop servo control. The trim angle is the angle of the motor in the water. The optimum trim angle varies by motor, boat, conditions and speed. Not sure that engine height changes make much difference. Re: Correct height on the jackplate? The boat on the left has an inboard or sterndrive motor and the boat on the right has an outboard motor. This reduces the power of the propeller, especially its push on water. If your outboard jet is cavitating, the jet pump is pulling more air than water. Sometimes for a seasonal year, sometimes for 5, 10, or even 15 years! Outboard manufacturers are now recommending that engines be mounted higher than the old standard, provided boat speed justifies it. The brackets can add 1 inch to the overall mounting height of the outboard. The mounting height of an outboard motor can impact the speed and handling characteristics of the boat. The proof of proper mounting height will likely be when operating in rough seas. It acts like a trim tab for your motor.Bend it up and it'll dig down, bend it down and it'll raise up. An adjustable height outboard motor mounting to be secured to the transom of a boat and support the mounting brackets of the motor, comprising: a. a plate overlying the outer surface of the transom and For over five years he has worked as a newspaper reporter and historic researcher. Industry standards dictate that for short shaft engines the transom height should be 15″. Open up an outboard and this—hugely simplified—is what you'll find inside: 1. Yet it’s good to know the basics of outboard setup so you understand, for example, why the dealer might recommend changing the outboard motor mounting height of the new outboard. Showing the height of Cavitation Plate relative to bottom of the boat. Outboard manufacturers are now recommending that engines be mounted higher than the old standard, provided boat speed justifies it. After reading through this quick guide, you should have a pretty good idea of whether or not not you have your outboard mounted at the correct height. As a yacht designer and boater, I prefer longer shafts. Bass Cat Boats wrote: Engine heights are like lower unit lengths. At speed, the prop runs in a hump behind the hull and the bracketed outboard can have its cavitation plate 2" higher than the bottom of the boat. All outboard motors have an adjustable trim angle. The rig steers much much easier now. Propping may affect the cavitation, however without creating the "adverse effects." The outboard in Figure 8 is at exactly the right height for a moderate speed. Variables to consider when determining the mounting height include the 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. The motor mount of U.S. Pat. Outboard motor height set up. USER SINCE 6/13/02 PROFILE BLOCK USER. Here are some things you should look for, whether you’re buying an auxiliary outboard or considering how to install one. 2. You do not adjust the set back to match a given motor height. 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. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines. The anti-ventilation plate â or cavitation plate on an outboard motor should be no more than about 25mm below the bottom of the hull centre. There are three main trim angles. I can only see the ridge a couple inches above the cavitation plate. After much tinkering, we managed 60 mph at WOT (5800 rpm). 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. Top-of-the-block water temperature should not be allowed to exceed 140 (60 C) while water pressure at full throttle should not be allowed to fall below 70% of the full throttle reading taken at a more conventional transom height Sport Fishing Magazine may receive financial compensation for products purchased through this site. In fact, a growing number of boat builders are building their faster outboard-powered boats with transoms 1" to 3" above the standard height (usually 20"). High Thrust Most engine makers offer specialty engines with lower gear ratios, fitted with larger diameter propellers designed to provide more control at low speeds. Reply STO says January 6, 2014 at 4:31 pm We just purchased a 13 foot Jon boat (Wide) with a 30/25 Mercury EFI Jet. How to properly rig and setup an outboard engine for top performance. Propeller diameter also can affect the ideal engine mounting height. No. Things in life happen and there are many different reasons why a boat ends up sitting around. To achieve this, the motor itself has to be attached at the correct height. I've read here and there that proper mounting height means you should be able to see the top of the cavitation plate. Raising the motor increases the speed of the boat while decreasing the effort needed to turn the boat. 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. A typical rebuilt midsize outboard motor from the 1980s to 2000 between 90 to 115 horsepower will cost at least $3,500 if purchased from a discount dealer; it will likely cost around $4,500 if purchased from a local full-service This also means it can affect the safety of the boat. Thus the engine is properly measured in ⦠You are constantly trying to get your boat to run on a smaller wetted area and you accomplish this with the leverage your motor and prop can ⦠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. The Long shaft standard gearcase is a 20" case. Remember, you need to find the best motor height for a given set back. I can't see mine, when on plane. It also decreases the boat’s lift and increases the time it takes for the boat to reach plane. Measuring Motor Height Figuring out how to measure motor height on a bassboat can be a bit confusing at times; hopefully this will help sort out the confusion. This exhaust port should be about 1 inch above the water line when the boat is idling. The Cavitation plate keeps the prop in the sweet spot. What Should You Do If An Outboard Has Been Sitting Still working on engine height and prop set up Some bay boats and flats skiffs also have jack plates to facilitate adjustments in outboard motor height. The AV plate is "skimming" the waters surface at WOT, with water pressure holding steady at 22 psi. The motor needs to be set at an optimal height because it causes propeller ventilation issues if it is too high. The lower mounting process causes the engine to be set lower as well, which gives a poor outcome. Outboards designed for saltwater applications usually have longer shafts. Boats with extended transoms, brackets that extend the mounting bracket for the outboard motor behind the back of the boat, can use a higher outboard height. There is a balance between motor height with the jackplate, trim of the motor, and how the driver handles the steering wheel. ADVERTISEMENT Based on what I learned in the process of wrenching on outboards and talking with representatives from major engine brands, here are topics you might want to discuss with the dealer … I'm thinking my dealer may have mounted my Etec too low, unless this particular boat demands it. Most transoms are in the 23" range for these engines and the actual engine height is in relationship to the lower hull. What size boat are you running that you want to hit 40mph with a 90hp? The rig steers much much Transom height for outboard motor directly effects the performance of the motor ⦠Max GPS speed was 26 and it would only stay on plain at WOT. In In How high should my outboard be mounted? Check you motor height. Steering to me is one of the big tricks. Transom Saver While they come in a lot of different styles and are made by numerous manufacturers, the general concept is a device that runs from the lower unit of your outboard engine to your boat trailer. You should get a motor with a shaft length that matches the length of your transom. I'll try to make this as simple and short as I can. On the flip side, if the outboard is set too low, it triggers enormous drag. I have a Mirrocraft 1615 troller with a Merc 40hp 4 stroke and from day 1 it just didn't seem right. Positive or negative. The height of the outboard is one of the most critical elements of setup, and that's why outboards have a series of vertically aligned mounting holes on the motor bracket, allowing for adjustment of the engine height. Remember as well that you won’t get any extra speed from an increase in HP. The mounting height of an auxiliary motor is quite a separate topic from the main motor. This part of a boat also is referred to as the transom. Need some help with my outboard jet, Mounting height, Spray Post by Backroads » 02 Jul 2014, 16:37 Ok guys, I'm in need of a little help and advice. It increases drag and underwater clearance, along with effecting travelling capabilities as more fuel and energy is used. This i… Switching from a small-diameter prop like a 13.5-inch Mercury Laser II to a 14.5-inch Mercury Enertia effectively lowers the swing of the prop blades by a half-inch. However, the motor should not be raised more than 5 inches above the standard position. Figure 9 shows a similar set up on a catamaran hull with the anti-ventilation plates right at the hull bottom. Sunset Red w/Bronze accent. Sandstone interior, Seagrass and Sunset Red canvas. The standard shaft length for most outboard engines less than 125 horsepower is 20 inches. Other factors to consider when determining the mounting height of an outboard are related to performance. contender posted 04-30-2010 02:17 PM ET … An outboard motor is an engine designed for small watercraft that mounts on the back, or stern, of a boat. Engine Height: Boat speed is simply the result of prop efficiency and forward thrust versus friction (wetted surface area). We found the best all around outboard performance height to be approximately 3 1/2" off the transom. This also means it can affect the safety of the boat. Motor height I would probably set the prop shaft at 4" below the bottom and mount the motor using the top holes so you can just unbolt it and raise it a hole at a time. This is one reason performance boaters use a set-back device between the boat transom and the motor bracket. For the auxiliary motor the shaft length and mounting height should be chosen so that the propeller is nicely immersed in the water and shows no sign of [ventilation]. this is the most inportant part of outboard jet setup. 7/22/12 @ 9:05 AM. Fuel burns in the cylinder (or cylinders) to make power. To correctly measure your transom, to determine what shaft length you need for your specific Jon boat, use a standard measuring tape to measure from the top of … This allows the engine to idle without the flow of the exhaust being restricted. My guess is the porpoise problem is the motor is too high already. Randy from Michigan 2016 SLX Premium 21' w/SPS and a shiny black 150. I’m going to install a 4-blade prop tomorrow along with a hydrofoil and see how this affects the ventilation. The mounting height of an outboard motor can impact the speed and handling characteristics of the boat. 2005 22ft tahoe tritoon conversion. We found the best all around outboard performance height to be approximately 3 1/2" off the transom. This is also known as the shaft length. The heavier your boat, the faster you drive it, the choppier the water, the more heavily loaded, or the lower in the water it sits, the more fuel you'll burn. Powered by the burning and expanding fuel gases, a piston moves back and forth in the cylinder. A special case is an outboard on a bracket. The motor is already a longshaft motor, and I’m not aware of these motors being in XL longshaft configurations (25"). 23" outertoons, 25" centertoon with 26" setback. A Bonnier Corporation Company. Is that consistent with different types of boats? I’ve always found the anti-cavitation plate method to be very reliable in getting Attention: Remember to measure the outboard shaft length straight up … An ELPT outboard is an acronym meaning the motor has electric start 2: The transom height needs to suit the outboard and ensure that the propeller will be in the correct depth … 2005 200xs Merc optimax. As someone else said, the cavitation plate should be about 1" below the bottom. At speed, the prop runs in a hump behind We claim: 1. When you initially purchase your boat you will have to select and purchase an engine as well. Some boats can house either an I/O engine or an outboard engine, but … Fig. SUBSCRIBE SUBSCRIBE ADD TO FAV ORTIES.