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Porpoising occurs when the bow rises for whatever reason but runs out of lift. C Capnredfish Registered Joined Jan 31 2012 3436 Posts 5 Jul 17 2019 I am betting on prop.
Weve managed to get the side to side movement out of it but then it started porpoising.
Why is my boat porpoising. A boat can porpoise because the weight in the boat is disproportionate between the bow and the stern. It might also be because of the trim angle of the engine and the mounting height of the engine difference. We review some of the most common reasons that your boat may porpoise in the water and ways to fix the troublesome issue.
Porpoising is the result of the motors outdrive pushing the boat upwards essentially boosting it out of the water albeit for a short period of time. Once the boat comes back down the outdrive will once again push it back out of the water. How to get my boat to stop porpoising.
Porpoising occurs when the bow rises for whatever reason but runs out of lift. It them falls back down and repeats the process. Too much aft weight is common on tin-can console boats and exacerbates the problem.
Try starting with the tilt pin in the lowest hole motor will be trimmed all the way in. If the boat is porpoising going up and falling down you either need to give it more throttle or trim down a little bit. When you slow down to maneuver in traffic or approaching a destination you may need to trim down to prevent porpoising at the lower speed.
At idle they are in the down position but as you move faster the pressure from the flowing water underneath your boat lifts the tabs into the appropriate position. In most cases the elimination of porpoising. And also a quicker time to plane faster hole shot and top end speed and even better fuel economy.
Too good to be true. Porpoising issues can be caused rocker in the hull engine mounting too low a bow lifting high rake propeller with not enough horsepower to carry the load too much positive trim poor weight distribution. C Capnredfish Registered Joined Jan 31 2012 3436 Posts 5 Jul 17 2019 I am betting on prop.
Or you want bow higher than it should be. Porpoising is caused by running too high a trim angle and moving weight forwards will decrease porpoising ie the opposite of running a heavier outboard. Porpoising is complex and is not easily covered in a few line explanation.
I normally have had to always run the boat 34 full down on the tilt to eliminate the porpoisingThis happens even when the rear live well is emptyFor whatever this is worth I can say that when I do get it trimmed out right and its running good the porpoising starts again once I slow down a bit or even more when I slow down even more coming into a spot or back to the landing. First off THIS IS NOT MY BOAT I am just extremely curious as to why this could be happening. A little information on the boat Shearwater 25LTZ w 300 Merc Verado hydraulic jackplate trim tabs power steering and other stuff not needed for this question.
Ok this boat is for my father-in-law and. Yep a prop can cause it to porpise. If they botched the repair job thats the first place i would start.
I had a raker for my old champ that i had fixed by a general repair prop shop and all they did was grind off the nicks and it was never the same after they were thru with it. Porpoising is probably caused by center-of-gravity problems as well described above. But is can also be caused by a sticky elevator that doesnt return to its neutral correctly or that overshoots.
A defective servo bad servo mount sticking pushrods or worn control arms can all contribute to this. If the boat is set up correctly it should stay on plane without porpoising somewhere around 25-30 mph. If you have to go 35 mph to keep the boat from porpoising then your boat is not set up properly.
Proper setup involves engine height propeller selection weight distribution etc. May 18 2010 at 312 pm 872729. I had the same problem with a tin boat I had.
What we did was put some wedges on the bottom where the transom meets the bottom and that will force the front end down. If you run your band across the bottom of most glass bassboats there is what they call a hook manufactured in to the glass. On some of the IFS coaches our Motion Control Unit MCU can help cut down on porpoising as well.
Sometimes controlling airflow into and out of the bags can help in some applications but not always. For example MCUs on some Freightliners. Weve managed to get the side to side movement out of it but then it started porpoising.
That made a huge difference. My next thought was to move the starting battery forward. Doing that would lose roughly thirty pounds from the rear and gain that same weight up front.
There is only so much room up front in these smaller boats. The slow porpoising is tolerable but why tolerate it at all if it can be cured. 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.
If the hull designsetup 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. The boat may also begin to hop or pound in a rhythmic pattern known as porpoising. Trim back down in small increments until the maximum speed and rpm are reached.
This is the boats most efficient trim position for running top speed. Porpoising begins as you motor picks up speed and raises your boats hull from the water reducing the amount of hull in the water – which means theres too little hull in the water to support the boat. Trim the motor down until the boat stops bouncing.
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ROGMAN88- I think I would try an adjustable spoiler or wing above the deck at the bow to calm down the porpoising. I do not like to add weight to the hull since it will cause draw in the lily pads. The spoiler or wing will have increased effect the faster you go with the air boat.
Porpoising happens because the stern of your boat is driven down by your motor which forces the bow up. This is exacerbated when a majority of the weight of the boat is in the back. Porpoising can also occur if you have too large of a motor on your boat.
Our boat needs a lot of weight up front in general but we notice that we have a problem with porpoising at 18mph or so with a lot of weight in back. More weight up front helps that problem and running at a faster speed helps too.