porpoising question HELP!!!!!!!

[airjohn81]

hello, i have a 10 x 6 baby gore hull that is practically brand new to replace my wore out one... the hulls are exactly the same !! i switched everything over( stand , cage , ect) and was a direct drop in... my old gore hull rode free as can be and would slide sideways for ever and was fast!!! the new gore hull isnt as free riding and when it gets planed out and gaining speed it starts propoising like a bucking bull!!!!!!! its has soo much more speed an can feel it wants to but damn it will buck right out of the seat!!! in real skinny water it rides like a dream!! ive moved engine stand back an forward no change.. shimmed the motor no change.. and the bottom from transome forward is straight!! i did notice with the hull on the concrete it has a very slight rock to it side to side... i do not want to run a trim tab if at all possible as the old hull never needed one... would a hull jack work?? an where to place it?? all help an opinions is really appreciated as im all out of ideas!!! thanks , airboat dave

[Papee]

How much did you shim the motor. The new hull I built porpoised the first time I put it in. I had to put in about 3/8 inch of shims but the front was also riding a bit high. It all depends how it is riding in the water once you have the engine shimmed the way you need it. If shimming it makes it plow then you'll have to check the hull for a dip and either fix it or use jacks.

[aerokirk]

A porpoising boat usually means that the nose is riding too high and needs to go down. If you have a speed boat and trim the engine too far up, it will porpoise, therefore on the airboat you should either add shims to the front of you engine or remove them from the back of the engine to force the nose down.

[Papee]

Also look around the forums here, I remember Chuck working on the back of a hull he even made a tool to fix it. It's either in one of his threads or Dwayne scharboughs threads. I'm always on my phone when I get on and its hard to search.

[airjohn81]

thank you for the responses!!! i do know my motor does sit high in the back ... ill try shimming the front up an see what happens... ive talked w chuck as well but apprehensive of taking a die grinder to a brand new hull!!! lol but i tell ya... that man has been SPOT ON with all the help an advise he has givin me over the course of my couple builds.. so i may have to cringe a little an let my hack the back!!! will update as soon as i do some testing... also what ever happend to the twin carb papee??? seriously interested in ditching the P.O.S. stocker..lol

[Papee]

Check out the new thread about the single carb. I'm just about to update it now.