rocker in hull

[87blf125]

i have a 87 bayliner bass boat 18 ft with a 1998 merc 150 efi. i have had problems with the boat porpoising since i had it and had a hydrofoil on it to mask the problem. i have just found that there is a small section of the bottom of the boat that buldges out some on the back 3 ft of my boat on both sides. my question is would that cause my porpoising and how do i fix it. also would is be easier to just replace the bottom half of the boat because i ma have a line on a cobra that i think has the same bottom half of the boat i have.

 

[bear_69cuda]

Re: rocker in hull

Not sure if that would be the cause? Do you have any pictures?

What prop are you running?

Ever thought of Smart Tabs?

 

[87blf125]

Re: rocker in hull

i am running a 23 pitch ss merc prop. the boat porpoised even with the old force 125 on it and i tryed a 17, 19, and 21 pitch with that. i did not want to try anything else like smart tabs because even the hydrofoil doesn't work perfect and i don't have the money to keep trying dif things that don't work. i can not even realy get on plane with out the hydrofoil and the motor trimmed all the way down. i am just trying to find what the true cause to this is, i have moved things forward in the boat, tryed sand bags in the front, tryed a jackplate. all i hear is there is probably a rocker in my hull that is causing it?

 

[87blf125]

Re: rocker in hull

i am running a 23 pitch ss merc prop. the boat porpoised even with the old force 125 on it and i tryed a 17, 19, and 21 pitch with that. i did not want to try anything else like smart tabs because even the hydrofoil doesn't work perfect and i don't have the money to keep trying dif things that don't work. i can not even realy get on plane with out the hydrofoil and the motor trimmed all the way down. i am just trying to find what the true cause to this is, i have moved things forward in the boat, tryed sand bags in the front, tryed a jackplate. all i hear is there is probably a rocker in my hull that is causing it?

also i can get about 45mph with hydrofoil on before it bounces but can not trim up at all. anything after 45 and it bounces even trimmed down all the way

 

[bear_69cuda]

Re: rocker in hull

What is a rocker? Sorry but I've never heard of that?

Smart Tabs really do work with issues like porpoising... And not that much coin...

 

[Yacht Dr.]

Re: rocker in hull

would is be easier to just replace the bottom half of the boat because i ma have a line on a cobra that i think has the same bottom half of the boat i have.

If you mean the HULL .. then ..NO.

Do you have any pics of this bulge your talking about ?

YD.

 

[woody66912]

Re: rocker in hull

Yes this is the root of your problem. I see you are in merrill WI. You might want to contact. Jeff's five star boat repair. Mondovi WI.
Phone # (715) 926-4239,

He might be able to grind that rocker out and put the hook back in , shoot him a call he does very good work.

 

[jbcurt00]

Re: rocker in hull

In addition to trying to 'fix' the rocker, you might try to discover what caused a large enough bulge on both the port & starboard sides of the hull bottom, 3ft long from the transom forward.

I can think of a few, none of them good. They sound much to large to be blisters in the gelcoat....

Pix would help.....

Hope you can get her back in the water, planing & running great soon

 

[bear_69cuda]

Re: rocker in hull

Can someone please tell me what a rocker is?

 

[bear_69cuda]

Re: rocker in hull

Nevermind I got it now...

I found this...

If the area of the hull bottom immediately forward of the transom is curved, the hull is said to have rocker. Rocker is a problem because it causes the boat to porpoise, or continually pitch up and down as it rides through the water. Porpoising destroys performance, and also makes the boat much more liable to capsize.

 

[jbcurt00]

Re: rocker in hull

The way that reads makes it sound like its the same as having a 'hook' in the hull. I took it to be the exact opposite of hook, a high spot that needed to be cut down, not filled in, when the boat hull is upside down & the bottom is facing up ~ A hill not a valley.

But neither would be good or a simple, easy fix I don't think on a fiberglass boat. And quite possibly only visual evidence of bigger problems below deck.

 

[87blf125]

Re: rocker in hull

i do not have any pics of the hull yet but this is a link to a video of what my boat does with out the hydrofoil. http://www.youtube.com/watch?v=3wXuLsFgrBE&feature=plcp