Bruntons H5 Autoprop whining at 1800rpm

[scr0che]

Brand new Bruntons H5 Auto prop fitted, but when the power hits 1800rpm it makes a whining/grinding noise in both forward and astern. Anyone have any knowledge on this kind of issue? I'm chasing Bruntons but not getting anything back as yet.

We took the boat back out of the water to check the installation, all good. 2 of the 3 blades 'flopped' down when raised, rotating 90 degrees, not the full 180 - maybe just a bedding in issue through use? The 3rd blade did not rotate when let go at all, so re-greased all blades and worked the grease in for a while to the point is started to behave like the other 2 blades - all 3 were full of grease anyway. Noticed in ~20 degrees of all the blades 360 degree arc a 'scrape/grind' noise, minor but there - is this normal? Engineer identified on 2 of the blades when turned no vibration on the shaft, but the third one did seem to vibrate somewhat (by placing a finger on the shaft whilst rotating manually), very minimal. Bearing issue? Prop alignment/fairing issue? This is a new brand new prop!!!

We only hear this at 1800rpm, that's the real odd thing about it, move up or down from that, forward or astern, no noise at all. Engine is a volvo MD22A on a HR36, gear ratio measured in the yard at 2.3 to 1, max rpm 4000. On a test run up the river, prop performed really well power wise in both forward and astern.

Any advice much appreciated, I'm still trying to get support from Bruntons.

 

[vyv_cox]

This is a very common problem on new propellers (and on dinghy catamaran rudders) The sound is due to a flow related resonance at the trailing edge of the prop, easily solved. You need to file a flat on the trailing edge of each blade, taking off the sharpness to a flat of around 1 mm width, maybe even less. I am attaching a photo that, although it was not taken for this purpose, shows my 'flat' on the lower blade.

Incidentally, my Bruntons is now well over 20 years old and well used but the blades still do not flop down. The initial stiffness that I expected to reduce with age has not, although the prop works perfectly.

 

[scr0che]

Further testing this morning and the whining is happening at 1400-1600rpm, and not 1800rpm as it was when tested yesterday. It's definitely more of a whining/singing. The guys in the

This is a very common problem on new propellers (and on dinghy catamaran rudders) The sound is due to a flow related resonance at the trailing edge of the prop, easily solved. You need to file a flat on the trailing edge of each blade, taking off the sharpness to a flat of around 1 mm width, maybe even less. I am attaching a photo that, although it was not taken for this purpose, shows my 'flat' on the lower blade.

Incidentally, my Bruntons is now well over 20 years old and well used but the blades still do not flop down. The initial stiffness that I expected to reduce with age has not, although the prop works perfectly.

Many thanks for this, I've not heard the noise before, first time for a new propeller on board. Bruntons have just called to confirm about the same - suggesting I use it for a season which may resolve it, if not to contact them and they will adjust the blades, I guess in a similar fashion as you have suggested. One point I noted from the conversation was that the noise would be different if tied on the pontoon whilst testing as opposed to going up the river - different streams, water flow etc.