PDA

View Full Version : Outboard making cracking noise under load!



dazz_1975
30-03-2008, 11:59 AM
The last two time I have been out in my boat a cracking noise has appeared when I accellerate fast or decellerate. The noise also occurs when when I hit waves fairly hard.

The noise seems to be originating from the outboard and I have looked all over the hull for stress fractures but all seems to be in place and it has led me to believe it is from the outboard.

I have put a bit of pressure from my hand by lifing the motor up and down and I cannot reproduce the noise. The only way is to go onto the water and accellerate fast or decellerate fast or hit decent size waves.

Does anyone have any idea what it is? The motor seems to be running smooth as always.

The motor is a 2003 50hp Yamaha 2 stroke basic model tiller steer.

I have searched these forums and could not find an answer so I thought I would create a new thread. Please be kind as I don't think I have posted on these forums before.

Any help would be greatly appreciated.

Edit: The noise seems to be getting worse. Even accellerating slowly now seems to create a cracking noise.

Cheers
Darren

Blackened
30-03-2008, 12:07 PM
G'day

Is it on a 14/15' tinny? If so, It's got to be part of the transom flexing and buckling the sheeting?

Dave

dazz_1975
30-03-2008, 12:14 PM
Yes. It is on a 2003 4.6 Quintrex Dory.

And yes I have read on these forums how crap Quinnies are. Its just that I did not read this forum in time before I read it.

The cracking has happened just recently. So I thought it might of been the motor. My father had the same problem with his 4.1 Stacer. He had a 40hp Mariner on the back of that. He said it might be bushes or something on the motor. I don't know nothing about motors so he could be right.

I suppose it is hard to find out whether it is the back transom which is buckling under pressure.

Blackened
30-03-2008, 12:24 PM
G'day

I'd be having a look at all the welds in the transom area, where it meets he bottom, side sheets and especially underfloor to the keel bracing,

Regards to engine bushes, Something may be a bit loose, but I doubt it.

Dave

bluefin59
30-03-2008, 01:15 PM
Have a good look under the floor if you have one and up under the gunnels as well ....matt

dazz_1975
30-03-2008, 01:24 PM
Looked under the floor and all looks fine. I lifted the false floor up and all looks fine. Only problem is that some of the supports are welded to the floor with is under the seat which I cannot get access to unless the seats are removed.

Cheers
Darren

Dan5
30-03-2008, 01:25 PM
Hey mate ,look is the boat painted/unpainted?...If unpainted you could get some dye penetrate from your local welding supplier to check properly for crack's,the instruction's on how to use will be on the packaging(very easy).It's hard to do a visual inspection properly unless the crack's are fairly large the dye peno will highlight any crack's and make them very easy to see.

look into this method for an absoulte answer to your problem's with cracking.

Dan..........

tunaticer
30-03-2008, 03:04 PM
I would nearly put money on the sheet in the transom is warping under load and popping the dish inside out so to speak. My tinny has done it all its life and the transom still has not cracked anywhere. Sometimes some boats develop that little bit of stress when they are welded and the plate likes to sit with a bulge either inwards or outwards a couple of millimetres. Throw a heap of force on them like and outboard does to a transom and its quite easy to get them popping against the cupping.

If you cant see any visible cracking anf the hull is dry after a trip or it holds water if you put the bungs in and fill it up with the hose then I wouldnt be persuing it any further.

Jack.

FNQCairns
30-03-2008, 03:24 PM
If the motor is just loose enough on the transom to move under pressure it can makes some strange noises.

cheers fnq

deathstar 3
30-03-2008, 03:32 PM
Possibly the bushes on the tilt cylinder, strut i think from memory they are nylon type material. Maybe they are cracked and it is the motor moving in those bushes.

Just a thought

Cheers John

outsiderskip
30-03-2008, 04:54 PM
mine was makin a racket at 300rpm found out plugs were stuffed

pete

Ally410
31-03-2008, 02:47 PM
I would nearly put money on the sheet in the transom is warping under load and popping the dish inside out so to speak. My tinny has done it all its life and the transom still has not cracked anywhere. Sometimes some boats develop that little bit of stress when they are welded and the plate likes to sit with a bulge either inwards or outwards a couple of millimetres. Throw a heap of force on them like and outboard does to a transom and its quite easy to get them popping against the cupping.

If you cant see any visible cracking anf the hull is dry after a trip or it holds water if you put the bungs in and fill it up with the hose then I wouldnt be persuing it any further.

Jack.
Ditto, have had the same with my tinnie since day one (7 years), still watertight and no cracking that I can see.

baitwaster
31-03-2008, 03:22 PM
Yep, definately the transom, Nicko's used to do it and he fixed it. Mine does it and I don't worry about it. I had a look for cracks when it first did it ( has done from brand new) and no welds are cracked and the boat doesn't fill with water. So I don't worry about it. I think Nico just put a plate to stiffen the transom from where the motor bolts on.

see http://www.ausfish.com.au/vforum/showthread.php?t=124487&highlight=click

Roughasguts
31-03-2008, 04:22 PM
Whack a few dings in the transom with a ball pene hammer, that will tighten the transom skin up. Then again it might not help either but at least you would have tried something.

tunaticer
31-03-2008, 04:41 PM
Whack a few dings in the transom with a ball pene hammer, that will tighten the transom skin up. Then again it might not help either but at least you would have tried something.


JEEZ its no wonder you got your name mate!!!

Jack.

BaitThrower
31-03-2008, 05:03 PM
Its not the transducer tilitng on the transom is it?
Often mine will tilt up a hard notch at high speed and cause a bit of a quick knock sound that can sometimes sound like a crack at the back of the boat. Probably not but worth double checking. I should tighten mine up a little but having it a little looser will mean if it hits anything, it will tilt rather than rip off ;)

tunaticer
31-03-2008, 05:08 PM
Whack a few dings in the transom with a ball pene hammer, that will tighten the transom skin up. Then again it might not help either but at least you would have tried something.


JEEZ its no wonder you got your name mate!!!

Jack.