BAD VIBRATIONS!

[MESS147415]

Hi everyone - took my winter project out for first time yesterday after getting safety cert - 16 foot ski boat with inboard 3.5 litre V8 driving thro velvet drive box and straight shaft thro bottom of boat to prop. Everything works fine but heavy vbration at about 2000 rpm and anything above 3500 rpm - runs fairly sweet at about 3000 rpm. Shaft is true to the eye and prop which is approx 13inch cast bronze item has no major dinks. Any ideas please for checking? thanks steve

 

[ziggy]

Re: BAD VIBRATIONS!

how about the cutlass bearing. i think that's what it's called. the part that supports yer drive shaft, right before the prop. took me a power squadron class that, if i remember correctly, said that the cutlass bearing must be within .003" of being straight with the prop. shaft. maybe that bearing is wore out too. <br />hopefully a real real boat mech. will come by and set ya straight. this i just my guess.

 

[steve n carol]

Re: BAD VIBRATIONS!

I am supposing that this 'vibration' was not there when you stored it last fall?

 

[MESS147415]

Re: BAD VIBRATIONS!

New boat project so dont know what it used to go like - my first time on water with it. Cutlass bearing has no visible play in it steve

 

[Laddies]

Re: BAD VIBRATIONS!

It sounds like engine alignment, in most cases of low speed vibration. The coupling and shaft are misaligned

 

[MESS147415]

Re: BAD VIBRATIONS!

I am tempted to run unit on land - with lube for cutlas bush via hose - and try with and without prop fitted to see if this has major effect - any comments on this approach please?

 

[Don S]

Re: BAD VIBRATIONS!

You probably wouldn't get the vibration with the prop off even if the alignment was way off.<br />Best thing to do is just remove the coupling bolts and check to make sure you are within specs (usually around .005 max.).

 

[MESS147415]

Re: BAD VIBRATIONS!

thanks don - prob is the coupling is about 2 1/2 foot from cutlas bush so undoing bolts will just allow shaft to drop and not allow alignment to be checked! you dont think it could just be a prob badly out of balance? steve

 

[Don S]

Re: BAD VIBRATIONS!

There should be a step in the coupling that keep it from dropping down.