PDA

View Full Version : 2000 Kamberra porpoising...



rc5695
05-07-2012, 01:42 PM
Porpoising: front bounces like going over waves when over ~35-40 mph

I don't remember the boat doing it when I bought it a couple of years ago, but did notice it last summer. Only mod was a bimini top I made, so i dismissed it as being from that last summer, but we went riding around Hartwell yesterday and it was doing it, with no bimini..:(..Hmmm...

Any other older boats doing it? Anybody have any ideas? Prop? I KNOW I've not hit anything and there are no vibrations...

ChrisK
05-07-2012, 01:45 PM
Do you have an adjustable wake plate on the transom? If so, try adjusting it all the way down.

rc5695
05-07-2012, 01:47 PM
Do you have an adjustable wake plate on the transom? If so, try adjusting it all the way down.
no wake plate and all balast is empty for testing purposes.... With my bimini on it starts around my 34-36 mph slalom speed :( I didn't test the speed it starts at yesterday. Doh.

bergermaister
05-07-2012, 02:45 PM
I get the porpoising at that speed too but usually don't run 35-40mph much. Get some people to sit further up in the front and you may be able to smooth it out.

I've also found if I do a quick cut on the throttle to drop the nose and then hammer it down again it will sometimes smooth out for a while. Just make sure you warn your passengers first!

New Guy
05-07-2012, 04:41 PM
RC are you trying to slalom? If not maybe add a little weight to the front. I know the more people I have in the rear of the boat the worse it will get.

rc5695
05-08-2012, 12:57 PM
last year w/ the bimini i was getting it while slalomming. i beleived i tried adding weight to the locker and it barely got better while making the wake bigger.

i just like to go fast sometimes...i did come over from an outboard remember ;)

bergermaister
05-08-2012, 01:20 PM
Just have all 15 of those kids sit up in the front. :rolleyes:

rc5695
05-09-2012, 01:24 PM
Just have all 15 of those kids sit up in the front. :rolleyes:
They are! Lol.

ChrisK
05-09-2012, 01:30 PM
Maybe try accelerating up to that speed a little more gradually. If you're just jamming the throttle down it could be throwing the bow up in the air, getting that first bounce in, and then never letting the boat plane out correctly. Maybe just accelerate slower all the way up to that speed and see if that helps.

rc5695
05-09-2012, 01:32 PM
Maybe try accelerating up to that speed a little more gradually. If you're just jamming the throttle down it could be throwing the bow up in the air, getting that first bounce in, and then never letting the boat plane out correctly. Maybe just accelerate slower all the way up to that speed and see if that helps.
Good thought... Thanks!

mmandley
05-09-2012, 01:54 PM
Another thing to look at is, is your bimini adjustable? I know on my Z5 i have the front tilted down a few inches so as the wind flows ofer it, the front is pushed down like a rear spoiler on a car. maybe your top is catching air and raising the front of your boat just enough to cause the issue. Like you said you didnt have this problem before and it sounds like thats the only real change.

rc5695
05-09-2012, 01:57 PM
Another thing to look at is, is your bimini adjustable? I know on my Z5 i have the front tilted down a few inches so as the wind flows ofer it, the front is pushed down like a rear spoiler on a car. maybe your top is catching air and raising the front of your boat just enough to cause the issue. Like you said you didnt have this problem before and it sounds like thats the only real change.That's what I thought too, except the bimini was NOT on this weekend, and it was still doing it...

mmandley
05-09-2012, 01:58 PM
That's what I thought too, except the bimini was NOT on this weekend, and it was still doing it...

Boo, well 2 options are more weight up front, or add a wake plate or trim tab type system. Weird how its doing it more now LOL.

maxpower220
05-09-2012, 04:59 PM
Time for a new boat.

mmandley
05-09-2012, 06:31 PM
Time for a new boat.

I agree with him. +1 lol

ChrisK
05-09-2012, 06:58 PM
The only other thing I can think of that might have changed is engine performance.

Let's say your prop was just barely providing enough thrust to keep your hull on plane last summer. Then, if something in your motor changed so that it's not delivering quite the same amount of power your prop won't be able to keep up with the speed you're wanting to achieve. So, maybe it gets it up to speed, loses momentum, regains it, loses it... porpoising.

Am I wrong guys? Maybe I have it completely backwards and you're over propped and your engine is now clicking on all cylinders? Still sticking with my earlier suggestion of just accelerate slower, that should help.

rc5695
05-10-2012, 01:45 PM
if anything i have increased performance with a new fuel pump & high-output coil... I'm going to try the slower accel...maybe this weekend ;)

boys, i'd love a new boat, but i'd hate the payment. Mines paid off to banks, but I'm still working on paying my savings account back. Lol. Only payment right now is the house, which supposedly leaves money for playtime :)

KSmith
05-11-2012, 10:54 AM
You could go low tech and try some Smart Tabs by Nauticus

bergermaister
05-11-2012, 11:14 AM
For some reason I was thinking it would be a lot more expensive to add a wakeplate setup. Check out this Ryan-
http://www.overtons.com/modperl/product/details.cgi?pdesc=Bennett-X-14-Wake-Tab-14W-x-12D&i=71228&aID=601N2&merchID=4006

Not too bad although I wonder if it is quite wide enough. EDIT: Just measured and my stock flat tab is 22" wide...

rc5695
05-11-2012, 01:20 PM
hmmm. Not bad, but i think i'd make a manually adjustable one first, to see if it did the trick... I'd already been contemplating it anyways, this might give me an excuse for another project. ;)

jmb
05-11-2012, 09:27 PM
I don't have a wake plate but I have a stationary plate on the back of mine for lift for skiing. This plate may help you problem maybe