Vibration at 4.5 knots

[Bruce]

I have vibration at about 4.5 knots under power. I have an atomic 4 (30 hp) engine. The vibration gets worse as I move up to 5.5 knots and then decreases around 6.5 knots. Any suggestions? PS. I had the cutlass bearing replaced last year.

 

[Rob R.]

Could be quite a few things....

I would check your engine mounts first - make sure they are intact and not split. They are easy to see.If those are okay, it could be a number of things - marine growth/mineral deposits/debris on your prop, engine misalignment, or a shaft that is out of balance or untrue.Quick question - did this happen quickly, or was the onset slow? If it appeared out of the blue, were there any other incidents that accompanied it? That might be a good starting point.Rob

 

[Bruce]

Vibration

Thanks,It has been vibrating to some degree for a couple years, it has just gotten worse and at a lower speed. I checked the engine mounts, growth and prop and all are okay. Is there a means by which I can check the shaft alignment or engine alignment?Bruce

 

[Rob R.]

None that I know...

But you could certainly ask the rest of the crew at this website. Engine alignment seems a bit tricky to me, so when I eventually get mine done, I'll probably have a mechanic do it. I might tag along though, so I can learn it myself.A great resourch to check is Sailnet, especially if you happen to have an Atomic 4. But you will find all kinds of lists on everything you can image about sailing. Good Luck, and keep us posted - I'd be interested in your findings.

 

[Graham]

Cutlass bearing?

Sounds to me more like a worn cutlass bearing. Had the same symptoms on my boat a while back...Graham

 

[Kevin]

I would check prop loading, maybe to much

Hello Bruce,One thing not listed so far is if the propeller is overloading the current engine. If the propeller is loading up the engine too much you will see adverse harmonics taking place at the point the engine should be achieving its maximum rated torque. Introducing to much fuel due to adverse loading of the prop causes to much pressure. I would check to see that the engine is capable of getting to the rated max Rpm’s.Hope this helps Kevin