It’s making your day boating a little less enjoyable. Is it stainless and was it polished before? This cycle will continue to repeat until either the boat's speed is reduced or the trim is fixed. Effectively what is happening is as follows: The boat comes up on plane and begans to accelerate. I have searched quite a few threads here and it seems that porpoising at higher speeds is a relatively common phenomenon. Trimming the motor too high for the speed you are running will usually make it occur too. I have a tiller steer boat and I believe all the weight in the rear contributes to the porpoising. You’re on the water, the throttle is opened up….but you can’t keep the bow from bouncing around. rks. Moving one battery worked wonders for my boat with porpoising problems. personal experience: never had water in the bilge at all except for one act of stupidity. Could try an old glass boat trick. Porpoising is front to rear bounce; the front hits a bump, then the rear hits the bump, and they both bounce independently of each other, creating an oscillating motion. Then buy a new prop and send it to Rich Boger, DAH, Lanier Custom Prop, or one of the several quality prop shops that can blueprint and build that prop as the drive essential for that exact hull as it should be. We are the original owners of the boat and it was purchased at Bass Pro in Bossier City, LA so I doubt they are going to be much help. While porpoising can be merely uncomfortable for passengers, it can also cause loss of control, which may result in injury or damage to the structure of the boat. What do people have on their boats, apparently Mailbu will swap my prop to a 945 or 950. This is caused be a handful of factors, but a … Steering cable replacement for 2002 700LX 17 Foot Nitro Bass Boat. Yes. Trim the motor down until the boat stops bouncing. But can the prop cause it to porpoise? Picture a porpoise leaping through the water and you get the image of what it’s like in a powerboat. You'll need to play with the trim to stop the porpoising....that's not a prop issue,..that's a trim/speed/weight & balance issue. Instead of the old hammer trick, make a wedge of bondo or J-weld on the outside edges of the transom to make a hook. When I trimmed it up, it just made it worse of course. philput. Baldwin, WI. Mine came form the factory at Quicksilver with a brushed finish. Depending on the reason your boat tends to experience porpoising, you may be able to reduce or even completely resolve the problem in a few simple steps: If these solutions do not improve or fix your porpoising problem, it might be time to try a Hydro-Shield. Share. Are you bobbing at that speed, no matter how you adjust your trim? Porpoising is a function of the lift generated by your hull, the deadrise of your running surfaces, and the trim angle that is needed to get that lift. I always store and trailer the boat with the plug out so there was no water in the boat. Winona, Minnesota. I can not afford $600 right now. Boat Porpoising, What best solution or product? The plug being in is not the issue. I am going to contact the prop shop that did the work and see what can be done. Posts: 211. Boat porpoising. It did not do it before the servicing. If there is too much or too little lift a boat doesn't run flat. Porpoising is a sustained, repetitive motion that causes a boat’s bow to bounce up and down out of the water, even in calm waters. This boat is going to drive me nuts! That is like dragging a anchor and is only a band aid. (If you can get them to replace it with a new one, WOOHOO!!!) When the trim is at a high angle, porpoising is more likely to occur. They swapped the prop and issues went away. BAD deal! Making changes to your motor height, engine setback, and propeller can also reduce the tendency to porpoise. May 17, 2010 at 4:23 pm #1267633. on my little 14.5' Ebko...I already have the engine in the minimum trim position (manual trim, first hole, pin closest to transom), I put the battery in front of the boat, but still as sson as I hit 38~39 mph it starts to porpoise. How to stop your boat from porpoising. Porpoising is the result of the motor's outdrive pushing the boat upwards, essentially boosting it out of the water – albeit for a short period of time. Could they have changed something that could cause it to start porpoising? Thanks. Similarly, it is asked, should … What if I don't have a friend that has the same size prop that I do. I now remember to check. I lost a bunch of speed and it didnt have the bite on the water that i had when it was new. But you know that looks can be deceiving. This is caused be a handful of factors, but a low-mounted motor is often one of the most common. Even worse, cavitation can cause vibration because of uneven prop loads and damage or break equipment. It looks like a perfect day for a cruise. Porpoising is a common problem that many boat enthusiasts experience on calm waters. As speed increases, the bow repeatedly rises out of the water until gravity overcomes lift and the bow bounces down, creating a rhythmic bouncing effect. Boats porpoise for a few reasons. Recently my dealer took out a boat (22 ft) and had the same issues. If it were me, I'd have the "repair" facility put it back to specs and keep it under the seat for a spare when it returns. most common instabilities, known as "porpoising," is a vertical plane, coupled oscillation in pitch and heave which occurs in calm water, and can be divergent in magnitude. Instead, the boat kind of bounces, alternating between diving and lifting as it compensates for the trim problem. I just had my boat serviced at a local dealer and I also got my prop machined due to some small nicks. Watch later. If porposing continues after verified factory measurements are returned, then you have another situation, most likely not prop induced, causing the porposing. I'm still sort of thinking that if it was adjusted up it's either going to allow the boat to ride higher and fly the bow a little more, or be one of the wildest riding bronco, Billy sons a … High rake angles and round ears tend to be bow lifters. Would adding a hydrofoil cure the porpoising problems? Anything else I should try? I always thought porpoising was caused by too many rpms, causing the rear of the boat to lift out of the water above its plane angle (which is determined by hull length) and causing the bow to dip down in the water and then bounce back out. Wow...that is really expensive. I did play with the trim, but it was porpoising with the motor trimmed all the way down. Basically, porpoising is the word used to describe a bouncing boat -- when the boat is bouncing from hull or trim combinations and not the water. haywood04. Here is a full article that I have written on 'Why your boat is porpoising… Porpoising may also occur when the trim on a boat is at an improper angle. I have never done any work or had to replace or even take off a prop for any reason so please bare with me. Add power to … I guess I will try and get in touch with the guy that worked on the prop after work today and see what exactly he did. I paid almost $100 to get the prop work done. magnum165. Porpoising is when a boat doesn't trim properly. Tap to unmute. 01-03-2012, 12:39 PM. Porpoising while under power, or under sail? Semi cleaver blades, 4 blades, low rake are qualities to look for. To move through the water like a porpoise, alternately rising above it and submerging. They will push the transom up and help prevent the porpoising but the boat is still tail heavy. What is my next option? 16' high tide flats boat Yamaha 90 sho with a prop tech 18p four blade. Group 31 tm batt and a motorguide wireless. If playback doesn't begin shortly, try restarting your … The loss of blade surface area was the culprit. Trim tabs are the same. To an observer on shore, it appears as though you are diving in and out of the water to crest repeatedly, as playful sea creatures are known to do. Porpoising: “Porpoising” occurs when the bow of your boat starts to bounce up and down as you run at a normal speed. I am going to call the guy that worked on the prop and talk with him about it. When I am running WOT and trim the motor up the boat wants to porpoise. Seriously though, porpoising is something we get quite a few calls on, and it is one of those terms that you hear about mostly with regard to RV’s. Cool......sounds like he's on the up and up then.......he'll make it right! Winona, Minnesota. It occurs when planning across smooth water. While this does not address any underlying problems with your boat’s hull, it is a quick solution that can make your ride more comfortable. October 20, 2010 ebuyersworld Leave a comment Go to comments. If the hull design/setup is 'prone to porpoising', the onset of porpoising will start at a velocity that triggers a change in dynamic center of gravity (often the hump zone). If the center of gravity is too far aft and the thrust axis is too low, the bow will rise as thrust raises the COG about the center of pressure, then, when forces balance, as gravity overcomes thrust, the bow will fall, and the cycle will repeat itself. First, if you have another good, recomended prop shop that can give a second opinion on the prop's true specs currently, use that in comparison with Merc's spec's and have it returned to the factory measurements. Either trim down a little until the porpoising stops, or increase boat speed slightly to create more lifting force under the hull. Sign up to get the latest on sales, new releases and more …, © 2021 Hydro-Shield. The boat did not do it before I took it into the shop. Participant. Check out the benefits of a Hydro-Shield, then get in touch with us if you have any questions. This cycle will continue to repeat until either the boat’s speed is reduced or the … Boat has a porpoising problem any speed over 20-23 the boat is basically unusable unless the water looks like an ice skating rink motor can not be trimmed up period, and tabs have to be used at any speed on plane, basically have to run tabs 50-75% down any time on plane and it still wont ride right Did he add steel and then grind/file back to proper spec....OR did he just file the nicks out and call it "fixed". Good luck. For a better experience, please enable JavaScript in your browser before proceeding. You can order them either way. There are many different ways of achieving this. I haven't tried yet, but I'm guessing more trim is only gonna make it worse, help, … Porpoising is a vertical oscillation of the bow that does not damp out on its own. In other words, the boat is still out of balance but the transom is being forced up which will prevent the porpoising. Either trim down a little until the porpoising stops, or increase boat speed slightly to create more lifting force under the hull. just had some cup added to mine and some metal added to the prop due to bungs...it was in the 175 range (I think).. Porpoising is known as a cyclic oscillation of the powerboat in relation to pitch and heave, with sustained or increasing amplitude. Bring it back to the Prop Shop that did the work? Basically the bow of the … Porpoising: “Porpoising” occurs when the bow of your boat starts to bounce up and down as you run at a normal speed. In some cases the dealers don't know how to set up a boat but the factory will have an expert. Participant. Want to learn more about how our skeg-mounted hydrofoil can help you protect your boat, save money, and achieve a smoother ride? Finally got a call back later yesterday afternoon from the prop shop and he was really nice about it. It had a few nicks from an "incident" involving a shallow boat launch and not trimming the motor up. I did play with the trim, but it was porpoising with the motor trimmed all the way down. The thrust from the motor is actually providing a boost that pushes the boat up and out of the water. Posts: 1,076. Your battery, fuel, and other heavy components affect how your boat performs. Keep sanding it down til you get it right. Porpoising Verb To move through the water like a porpoise, alternately rising above it and submerging. They swapped the prop and issues went away. Porpoising inception and the craft parameters that influence it are the subjects of the research described in this report. "the boat began to porpoise badly" or in our case to drive along the road, alternately rising and diving. Porpoise!.. I have an 18″ express with a 130 on it and as i am trying to trim it out at top end it wants to porpoise. Boat Porpoising Issues. The resolution to a porpoising problem with a hull design is most always addressed by causing the boat to run with less trim. Jordan's prop could look brand new, but the blades could be out of balance or slightly smaller due to being ground down..but nothing was added to bring it back UP to proper specs. You must log in or register to reply here. Porpoising, or the bow bobbing up and dow, is caused by over-trimming at cruising speed; there’s no longer enough hull in the water to support the weight of the boat. JavaScript is disabled. New prop plus work should be around $500-$600 retail. Unpowered, the most common cause of porpoising is a CG that's way too far forward and a lot of up elevator trim used to compensate. This is a phenomena which is specific to cars which rely heavily on … The reason these voids form is boiling of the liquid. Porpoising begins as you motor picks up speed and raises your boat's hull from the water, reducing the amount of hull in the water -- which means there's too little hull in the water to support the boat. Rain. Trim the motor down until the boat stops bouncing. Once the boat comes back down, the outdrive will once again push it back out of the water. In addition to helping your boat get up on plane faster and more efficiently, an outboard motor hydrofoil or stern drive hydrofoil from Hydro-Shield can also help solve your porpoising problem. Give them a call and they can tell you where the jack plate needs to be set as well as the optimum prop for you boat.