Why does my boat rock?

[benc]

When I get to higher speeds 40knots +... the boat starts to rock slowly from side to side, why would this be? and how would I sort it?

Thanks

Ben

[MeMe]

.....you lucky sod, came the cry from most of the Forum. Having recently endured the same experience, I found triming in helped but reduced the speed at the same time - a double edge sword as they say !

[benc]

im only at about 75% throttle... so would really like to sort it out... ill give trimming a go tonight.

Anyone in the solent tonight?

[Andre]

Originally Posted by benc

im only at about 75% throttle... so would really like to sort it out... ill give trimming a go tonight.

Anyone in the solent tonight?

Hi Ben

and this is the rib in question at LAmpton Marina. Nice looking beast

photo courtesy of Phil Chitty

[Squirrel]

I find the same thing, strangely its more pronounced in flatter water, a bit of chop seems to have a damping effect.

I think it might be due to steering movement having a much greater affect at speed, try and keep your steering adjustments really small. Trimming helps too, but slows you down.

[Matt]

Chinewalking?

[benc]

Andre, indeed it is! They are the guys who work out the marina... they looked after getting it in/out of the water at LHampton marina for us.

Yeah, I love the boat - but ribs are new to me - as is two engines!

MadMat, sorry I dont understand the ChineWalking term :$

[Petrov]

Ben;

Do you have a pic taken from behind on shore.
Hard to se on the picture but they maybe look little high installed.
Take them down 18mm can sort the problem if they are to high.

[Petrov]

Hmmm, does it excist a counter rotating Yamaha 115hp.
Otherwise that could be the problem, 2 right rotating engines will push the boat to the side when driving and when you coming up high speed you get less wet surface and than balance of boat will be more effected.

[benc]

Petrov, sorry I have no prictures from behind the boat with the engines down, I have always had the engines up while it was been out of the water.

Interesting about the engines both spinning the same direction, I will take a look tonight, this could possibly be the case.

If it is, is it possible to change the direction at all, or does it mean a whole new engine?

[Petrov]

Hi Benc;

A whole new engine but i dont think Yamaha has a couter rotating 115hp.
I can be wrong, will check on Yamahas homepage.

[benc]

Hmm, is there not another way this can be adjusted?

[Petrov]

Hmm, is there not another way this can be adjusted?

I was wrong, they have counter rotating in 4-stroke.
Than i would guess that the engines are to high, my old boat had 2 X 300HPDI and only 8,2m long boat and my wobbeling came around 59-60 knots.
I lowered the engine and it disapered but than i got the galopping effect instead.
But the boat was a little over powered, with 2 X 250 i would never have the problem.

[benc]

ok, ill have a look tonight

Thanks

Petrov

[benc]

http://dogscogs.com/gallery/album01/DSCF0765?full=1

Hmm, edited as it didnt make sense

Looking at this picture, it looks as though I already have one counter rotating engine, as it looks like the propellers spin opposite ways.

[Petrov]

Yes it`s a counter rotating, it`s really hard to se on pic but they maybe look little high.

[PeterR]

Have you tried putting extra weight on bow before you adjust engine height this will help

[Andy]

Give Barnet Marine a call and ask them. Laurence Lock is your man, he knows all there is to know about Tornados

[benc]

Thanks for the suggestions guys, I tried to go down and try adjusting trim today - but when I got there found my battery was flat so going back again tomorrow night hopefully. and this weekend is meant to be nice so will play then if not.

[Hightower]

And check for play in the steering system.