New Yamaha 8hp

[Colthecops]

Hi folks,

I’ve just bought a brand new 8hp 4 stroke Yamaha outboard.
I use it for trolling at slow speeds and I’ve noticed that there is quite a noticeable low rumbling sound that seems to be coming from the shaft. The outboard also vibrates quite a lot.
When I put it in reverse or neutral, the rumbling and vibrations disappear completely.

I've checked the prop for fishing line etc and everything seems ok, plus I’ve put some rubber strips under the clamps but it hasn’t helped.


I had an older Yamaha 8hp before this one and it had no vibration and sounded like a sewing machine with no low rumbling at all.

it would be a bit of pain to have to take the outboard back to the dealer so I thought I’d ask on here incase it’s an easy fix.

Any help would be much appreciated!
thanks

 

[99yam40]

could be the prop
or one cylinder not firing properly

 

[Colthecops]

Thanks for the reply. It’s a bit strange that when I’m in reverse, the noise/vibration completely disappears - even if I’m going quite quickly.
The prop looks ok, I bought the engine less than a month ago

 

[Sea Rider]

Could that be due to the clamps themselves are vibrating once secured tight onto the rubber patches, try to adjust both clamps ears to face each other, secure tight with a rope. The motor has a bolt side of the swivel bracket that increases/decreases the steering load, if too loose the motor might vibrate, adjust it to a point that when the tiller is released the boat will keep running at a straight watercourse. Check both scenarios.

Happy Boating​

 

[Colthecops]

Thanks for the reply. It’s a bit strange that when I’m in reverse, the noise/vibration completely disappears - even if I’m going quite quickly.
The prop looks ok, I bought the engine less than a month

Could that be due to the clamps themselves are vibrating once secured tight onto the rubber patches, try to adjust both clamps ears to face each other, secure tight with a rope. The motor has a bolt side of the swivel bracket that increases/decreases the steering load, if too loose the motor might vibrate, adjust it to a point that when the tiller is released the boat will keep running at a straight watercourse. Check both scenarios.

Happy Boating​

thanks for the reply.
I have a moto-lock over the clamps which holds them tightly in place so I don’t think it’s that.
I’ve used the same lock with two previous outboards and never had an issue.

I have the steering load set tight too, it won’t veer off course if I let go of the tiller.

thanks for the message though

 

[Colthecops]

Hey guys, quick update on this… I’ve noticed there is water coming out of the shaft of the engine (not the telltale but on the inside of the shaft). Is this normal and could this be causing the rumbling noise? The cowling is vibrating too but I can fix that by tightening the bolts at the front I think.