Aquadrive 19100 Mini coupling trying to isolate the noise?

[petergarth]

I installed this Aquadrive and its run perfectly for about 2500hrs.

I am now getting a little light knocking noise when the engine is running without load (idling along slowly).
As soon as I put a little load through the prop it disappears.

I can't decide if it's the cutlass bearing or the CV joint.
The cutlass was replaced about 500 hours or so ago so I'm doubtful it's that. It has a very slight amount of play on the shaft but in my opinion not excessive.

The Aquadrive doesn't get hot or make any noise under load. I've recently checked the grease in the bellows and all looked good.
The boat is being hauled out in a month or so for the usual, anti foul paint and maintenance.
Before I buy a new cutlass or strip the Aquadrive's CV (not something I'd like to do), has anyone had a similar experience?

 

[Boater Sam]

The splined shaft in the Aquadrive is known to wear. I reassemble them with Loctite. Having said that it is more likely the shaft bearing if you can feel any play.

 

[petergarth]

Hi there apologies for the delayed response to your comment Sam.
Looking at the diagram of the 19100 Mini Aquadrive I cannot figure out where there would be a splined shaft in the unit.
Can you point me to a drawing or try to explain what you mean?
Many thanks

 

[petergarth]

OK so I figured out that the 'axle' shaft connecting the two sides for the CV joint must be splined?
You say the splined shaft is inclined to wear. You would feel this wear once you've cleaned up the CV?
You use Loctite when reassembling and I expect before greasing?
I've watched a few YouTube CV joint rebuilds (for motor vehicles) and I suppose the Aquadrive is similar in principle. But nowhere do they mention wear on the spline?

 

[Arcady]

Just a thought, but do you have rope cutters installed by any chance? Might they have been disturbed when you re-fitted the cutless bearing? On a previous boat I found the cutters would make a clicking noise under very light loading.

 

[petergarth]

Thanks good thought but no I don't have rope a rope cutter fitted.

 

[Bilgediver]

Thanks good thought but no I don't have rope a rope cutter fitted.

i would suggest you check the Aqua drive by holding the engine side firm and trying to turn the shaft side back and fore. There should be no play. If there is relative movement it should be easy to determine if it is in a spline or the CV joint using a similar process and holding fast other parts.