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-   -   porpoising and chine walking.....what cause's it?? (https://www.offshoreonly.com/forums/general-boating-discussion/40108-porpoising-chine-walking-what-causes.html)

Ike 01-02-2003 02:27 PM

My 28 apache porpoised and i was told it was because that they were built with a rocker bottom which makes it faster. When i ran with my 25 three blades it was worse than when i ran the labbed 27's at cruise speed.

Ike 01-02-2003 02:35 PM

It only did it at cruise, but at full throttle it was smooth and strong.

Apache22 01-02-2003 03:10 PM

I'm not believing the drives are wiggeling urban legend. If so they would do it at 1/4 trim or no trim.

Chine walk comes into play when your trim out, you are riding on the rear most part of your hull, you have so much hull out of the water that the torque of the engine, through the drive, is torqueing the boat till one side of the hull hits the water and starts the effect of the hull going back and hitting the other side, and re[eats itself over and over.

Depending on your prop, if you are chine walking slowly you can counter steer to the chine walk and drive through it.

Prop can help alot, prop and tabs can dp away with most all of the chine walk.

jawbreakerkid 01-02-2003 03:12 PM


Originally posted by later
Hey Tbone that wouldnt happen to be the teal graphic 38 with blower motors is it, every time i see that boat running it is porpoisin real bad.
later
Dave


the weight distribution is quite common on some of the older straight bottom cigs with big power and big drives. it can be corrected if properly addressed. usually they will lie down as you lean on the throttles, but some get exponentially worse as speed increases = wrong setup! it isn't as noticeable in big water conditions.


dave- yeah, that is it. i think he is running #3's w/ boxes.
chad

Dixie Doug 01-02-2003 03:29 PM


Originally posted by bobby daniels
SOME BOATS AT SPEED START LETTING THE DRIVE OR DRIVES START SWAYING BACK AN FORTH WITCH WILL GET WORSE AND WORSE AS YOU GO FASTER,, WITH OUT HYD. STEERING ,SO AD HYD STEERING AND ALOT OF TIMES IT WILL CORRECT THIS CHINE WALKING

388 'S HUSTLERS DO IT DUE TO TO MUCH LIFT BUILT IN THE HULL TO GET IT TO RUN IN THE 80'S ,,,,,,,A WHILE RIDE AFTER 95 EVEN WITH STEERING :D :D

I agree,I think you mean external hyd. steering.I rode in a 388 trip 525's didn't do much chine walking after 95

Smitty 01-02-2003 04:07 PM

ANY play at the drive will cause chine walking. I added external hydraulic steering to my boat after adding 200hp and it still chine walked. Even with the steering I still had slop in the gimbal which I am replacing this winter.

It was different based on what prop I was running. Some props made the boat react different depending on if it was a cleaver style prop or a round ear style.

bobby daniels 01-02-2003 04:40 PM


Originally posted by Wally
Bobby, how can a boat have too much lift? I guess there has to be a compimise but i thought the less wetted surface the better.....to a point ofcourse.... :)
HEY WALLY YEP YOUR RIGHT TO A CERTAIN POINT LIFT IS GOOD ,388'S HAVE ALOT TO MAKE THEM RUN BIG NUMBERS WITH STOCK POWER ,I'VE BEEN IN PLENTY OF HOPPED UP 388'S NO FUN AT ALL, AT 95 ON ,,,,THEY GOT THERE CLAIM TO FAME FOR SPEED IN THE BOAT CALLED " BLACK CLOUD "TO RUN BIG NUMBERS AFTER RETOOLING THE BOTTOM REAR CORNERS OF BOAT TO TAKE OUT LIFT ,SO YEP YOU CAN HAVE TO MUCH OF A GOOD THING ,, THEIR FINE WITH STOCK POWER

bobby daniels 01-02-2003 04:43 PM

YOUR RIGHT DIXE DOUG I MEANT EXT STEERING AND A TRIPLE 388 HAS SO MUCH WEIGHT IN REAR ITS MOST LIKLY STABLE TO A POINT ,,THANKS


PS ANYTHING AROUND 100 YOUR GOING TO HAVE TO DRIVE WE ALL KNOW THAT IT JUST IF ANYTHING IS LOOSE ON STEERING IT MAKES IT WORSE

HOUSTONPROP 01-02-2003 04:43 PM

several things,but the prop is a big factor at the height of the power curve of the motor ,if the prop is not correct pitch and size it can cause loss of power droping the bow and then the motor trys pulling it back up and does but it can not keep it there so it falls back down causing poporsing,especially at the speed you are talking about midrange,also too much trim,a hook in the bottom of the boat ?just a suggestion of many factors.

birdog 01-02-2003 04:46 PM

That was cold Nort..............just plain cold ............:D


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