HELP! My boat is "Rolling" at unexpected times!!!

[Yakkasalive]

Hi All,

I have a 4.5m halfcab with 75hp merc on the back, I've only used it 2wice because it scared the s*&t out of me, this happened on smooth and open water, can u help?:

Under a fair bit of throttle on the plain the boat began to roll to one side and sort of 'grab' or just start 'banking' fairly hard, it felt really bad and was hard to control, I don't know whats wrong, maybe the aftermarket hydrofoil has been installed incorrectly or is bent? could it just be unbalanced (due to weight inside cab, etc)? Maybe an incorrectly installed outboard????

Any suggestions guys????

Cheers, Troy

[dan099]

sounds like it is broaching have u tried to lift the bow out with more trim

[Gbanger]

what brand of boat, also if you can post a pic of the stern and motor, from the side.. to see how the motor is mounted..

[seatime]

Yakkasalive, try removing the hydrofoil, check OB is mounted on the boat's centreline and is straight up and down, cav plate shouldn't be below the bottom of the hull.
It sounds like an OB set-up problem.

Steve

[SeaHunt]

Yakkasalive, try removing the hydrofoil, check OB is mounted on the boat's centreline and is straight up and down, cav plate shouldn't be below the bottom of the hull.
It sounds like an OB set-up problem.

Steve

Almost definately hydrofoil.
Had the same thing exactly, on a half cab as well.
If the Hydrofoil can flex at all you are in big trouble, especially if you trim the motor up, one wing is bending and digging in. Get rid of the bloody thing before someone gets thrown out or hurt.
If the boat really needs one get a SE Sport or one of those alloy ones called Pen something.
:(

[joey_1987]

From what I have heard, hydrofoils can be very dangerous but they can also help a boat get on the plane quicker and easier. As someone else said, a flexing hydrofoil is a recipe for disaster. If you remove it and find that you want to still have one on because of planing at lower speeds etc, then as someone else said, get an alloy hydrofoil (one I have heard good things about is Permatrim them, google them and call about them). I have heard horror stories about foils making boats turn extremely sharply, I don't have one and don't think I need one either because my 3.95m tinnie with 30 horsies gets up and goes even with 4 large blokes and gear onboard. Joey.

[SeaHunt]

Permatrim that is the name I was trying to remember , thanks Joey.
I would have got one myself but I had already bought an SE Sport a couple of weeks earlier when I saw them at the tackle and tinny show.

[Yakkasalive]

Thanks guys, I'll try and get a photo tomorrow, I'll try it with the foil off I think,cheers,

Troy

[bootyinblue]

Yakkas,

Did you solve this? I was hunting through old threads and found your problem. I have the same issue and have posted about it a few times on here. I can make my boat do what you describe 'on demand' now.

Dangerous.... but very impressive!!

[Deiter]

Hey Booty, i remember your post about the boat wanting to do 360's along the centreline at speed - where's the video???? would be good to see what can happen when things aren't quite right.

Damo

[charleville]

I recall a bloke who used to work at Mercury once told me that Merc used to sell hydrofoils as an add=on but stopped doing that after a couple of boats turned over in the USA when doing fast turns.

Aslo a boat that is full of water will handle in the way described. Use the bilge pump to see if you have water sloshing around under the floor.

[Andfish]

Yakkas,
Take The Foil Of The Outboard,same Thing Happened To Me,but I Got Tossed Out Of The Boat, Frightening The Hec Out Of My Wife, But To A Lot Of Amusement To My Daughter.don"t Let It Put You Off, Take The Foil Of And Try Again, You Will Be O.k.

[Hagar]

My two bobs worth . Have owned a few boats and driven heaps more . The foil may be at fault but I reckon properly used their advantages outweigh the minuses . I have had this happen to boats I was driving a couple of times and it does get your attention bigtime I have to say . In both cases the boat had max people on board who may not have been evenly distributed and the trim had been left full nose down . The hull nosed down and then wanted to run on one side of the vee until the nose was trimmed up - very quickly . It's surprising what too much weight forward can do to a hull . Good suggestions already to check for trapped water underfloor and steering / outboard security . If it is doing this in a straight line with nobody moving about to shift weight or you turning the boat - trade it in >:( >:(

Chris

[Chimo]

Hi Yak

You never did answer the question put earlier;

"What brand of hull is it?

Also is the 75 Merc a 4 stroke?

Cheers

Chimo

[charleville]

Hi Yak
By the law of averages you are more likely to be killed by a flying champagne cork than by a poisonous spider.Chimo


Only if you go boating in a cruiser. :-/

If you don't go boating in a cruiser, you are more likely to be hit by the wake of a cruiser, especially around the 'Pin on a weekend, or in the Broadwater.;D

[Chimo]

Hi Charleville

So you have been on Pinhead's boat too heh?

Chimo

[Searaider 2]

Hi Yak ,
I definitely think thats its the foil .

I had one fitted on both my smaller boates , before working my way up to my current 6mtr Allison .

The first boat was a 4.5 meter Tinny with a 40 Hp old mariner , it was a bit underpowered so I installed a Stingray type plastic foil & it turned it a new boat , it was excellent .

Then I got a 4.6 mtr runabout Quinnie with a 1/2 pod with a 60Hp Evinrude

Went WELL but dropped of the plane pretty quickly & was a little bit nose up taking off untill I got a bit of speed up & then It was fine .

I thought I know how to fix this I'll fit another foil / Stingray .
Next Trip out after fitting the stingray , I took of like normal & the boat was very sluggish & I couldn't get over about 3,000revs ???

My deckie got up & was going to have a look to see if we had picked up something on the prop .

As soon as he moved , the boat did a savage turn to port & laid on its side , just about threw us both in the drink .

After some more investigation , trying various Trim settings , it appeared that the foil was just working too well & trying to lift the stern of the boat out of the water .
When getting a bit of speed up the foil was working to well as a hydrofoil & forcing the the bow of the boat into the water .

End result , I gingerly tried to take off again using more outward trim , found it better , but the boat was that flighty on minimal trim movements , we came straight home & took the foil off .

Problem Fixed !!!

To get around the original problem ,when loading up , I just kept some more weight up the nose of the boat .

After that I heard of some other guys with similar problems fitting foils to smaller type boats that had plenty of power , but just a bit ass heavy getting out of the hole .

If you take the foil off & it fixes the problem , but still want some addition lift at slow speeds maby you could playaround trying to lift the motor , or reducing the lift by cutting down the surface area of the foil ???

Best of luck .
Peter
Searaider 2

[Dirtysanchez]

I agree, give the foil the ar$e
I had one on my old half cab, then got the motor rebuilt and ran it in, then took the gan out on the water for the day, most of the gang sat in the cabin as it was hot and sunny.
I got the boat up on the plane and thought how good it was that it would plane so well with 3 adults and a child, then it pendulumed from one side to the other then sat on the port side with sheets of water flying into the boat!! Holy $hit says the Mrs..

Took it back and the mechanic said Oh yeah, forgot to tell you that you wouldn't be needing that foil now you have so much more compression !!

I told him I was going to send him by family's brown undies in the post.

[ryank]

hey mate.

if the bottom of your boat is sort of round and doesnt have a big v at high speed they tend to roll to one side. or it could be as simple as unbalanced.