Brunton Auto Props

[Will_M]

Hello all!!

Who has actual experience good or bad of the Brunton Auto Prop??

The reason I asked...

Having just fitted one, these are the results. Max achievable rpm has increased although within the correct operating parameters of the engine. Boat speed is the same as was with its 3 blade fixed propeller. At the high rpm range cavitation is now felt from the Auto Prop. Generally vibration has increased.

Everything is in very good order, ie shaft bearings, engine mounts etc etc.


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[Shanty]

After much thought, I fitted one of these last winter. So far, I'm impressed - max speed under power up by about 1/2 knot, and under sail up by about 3/4 knot. On the downside, I get slightly more vibration under power - but the autoprop is a two blader replacing a three blade fixed prop.

These things are incredibly expensive, but in my case worthwhile. The alternative was to go for a folding prop, and install a larger engine to drive it.


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[JerryHawkins]

I have an early (circa 1990) 3 blade unit - H5 hub with open (water lubricated) ball races. I have no vibration at normal working rpm, but I do get strange "clunking" noises at tick-over rpm.

This was on the boat when I bought her, so cannot compare with fixed blade unit. I replaced all the bearings a couple of years ago and adjust them for free-play whenever the boat is out of the water - very little adjustment needed.

I have found that stopping power is incredible, but you do need a "handfull" of revs to "set" the blades when changing from ahead to astern when coming into the marina berth.

Overall, I'm happy and would probably go for another AutoProp when I change boats.

Cheers,

Jerry

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[Robin]

Ours too is the older open bladed version and came with the boat. We also get a clunk on engaging gear and a slight rattle at tickover in gear (on a Yanmar 44hp). It does take a while to get used to after a fixed prop, for example if you just engage gear at tickover in reverse in your berth, nothing happens and you look to see if a spring line was left on! As you say you need a bunch of revs to set the blades when engaging gear, then dropped back to normal. From talking to another owner with the same boat as us I do believe we get much better cruising speed for lower revs than his fixed 3 blader. We do 6.7 kts at 2000rpm (max is 3600). The effect of wind and sea is also different, just a little wind from ahead drops the speed, but this is easily regained by increasing revs slightly. A little wind helping and the speed quickly goes up, to say 7.3kts for the same 2000rpm. Stopping power astern is very good and no doubt that sailing performance from less drag has to be much better especially in light airs. Head seas also take speed off quickly if the revs are left the same, but the speed is quickly restored by increasing the revs. I think head winds and/or seas cause the prop pitch to reduce (like changing down a gear) so you need to increase revs to compensate, the reverse being true with a helping wind when the pitch goes up, like in overdrive.

Overall I am also pleased with the performance and would go that route again. It has to be much better under power than a folding prop (ours replaced a folder for the previous owners) without detracting from sailing performance.




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[wadethom1]

I have had an Autoprop 3 bladed 17 inch prop for about five years. It has certainly
improved my boat speed by about 1/2 knot under power and about 3/4 knot when sailing.The only problem I have had is the bearings have needed replacement almost every season. |It has the water lubricated bearings and Brutons have not been able to say why it has needed such frequent bearing changes. Has anyone else had this problem?

<hr width=100% size=1>RWT

 

[ashanta]

This has been interesting. I too am looking to change from fixed two blade prop but I was looking at the folding prop as I wanted to improve my sailing speed. Is the the performance under power significantly poorer than the fixed props and the brunton type self pitching props or is it just when astern?

Regards.

Peter.

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[sailorman]

i have a "max" prop its fantastic ahead & even better astern, although they also "clunk" when engaging.
u could also try the Gori prop which is similar to the Max but has an "overdrive" setting allowing cruising at lower revs in smooth water

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[Oldhand]

Your response is not surprising, water has no lubricating properties and thus I have always considered the ball bearingings in the Autoprop to be an unsatifactory design and thus have never used one. If you motor in water with a lot of silt, or even worse, sand, bearing degredation will be very rapid.

I endorse the view given on the Max-prop. Its excellent and am advised it will last a lifetime if stripped down, cleaned and re-greased during each bottom overhaul.

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[Robin]

Our Autoprop has the open bearings unlike newer ones which are sealed and greased. The bearings are not in constant movement like say on a shaft but merely to aid the free alignment of the blades, folding props don't even bother with bearings for a similar movement. We adjusted the bearings on ours on lift out after we bought her, the prop by then had been in use 6 years without any adjustment. Since then we have done a further 2 yrs without need to adjust and we are based in silty old Poole.

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[alan]

I would agree with all the positive comments made by the other replies. I fitted an AH last May on my Beneteau 311, replacing a fixed two blade. Improvement under power considerable; I can achieve the same speeds with 300 or so less revs. all across the rev range, and can also achieve the same maximum revs as with the old fixed prop (3100/3200 on Volvo MD2020) Under sail I gained around a knot, as predicted in the AH publishing.

Only downside I have found, that here in the Med, if I don't use the boat, the prop fouls up and then I lose around up to 500 revs from the maximum achievable with a clean prop. I have a friend who has a Maxprop on the same type of boat and he suffers the same fouling problem. Not such a big problem as up until mid-October, here in the Med, one can go down and scrape the prop clean regularly!! and in winter the prop fouls much less. I find the method of adjusting the pitch on the Maxprop "cumbersome" : it can only be done out of the water, so you are stuck until next haul-out if you get it wrong. My friend has trouble achieveing max revs without black soot coming from the exhaust despite a couple of adjustments to the pitch on his Maxprop.

I am very happy with the AH and would definitely buy one again if I ever change boats; even if they do cost more than the competition I would say the extra cost is worthwhile.

Antifouling: I have tried Seajet Pelclean (cost £50 !!!!) which I put on the AH from new in May; this lasted a couple of months when I was using the boat a lot, but I noticed when I was under water that there were lots of "marks" on the Pelclean as if it was being eroded by the movement of the prop in the water. By end of August the prop was fouled with crustacea and I had to scrape it clean. Next year will try thin coat of hard anti-fouling covered with lanolin and see if that works. I have done some static tests on my old prop with lanolin, hard-antifoul, and Pelclean ....... and the Pelclean seems to work the least, the best is lanolin. However, I need to put it on the prop next year for dynamic (i.e. moving in water) test.

Alan.
Nettuno, Italy

<hr width=100% size=1>Alan Cloke

 

[freedom44]

I lugged an Autoprop as hand luggage to USA, only to find it did not give the anticipated result, so took it back! Brunton were very good about it. I fitted a Max Prop instead, and am very pleased with it. I have altered the pitch 4 times and now feel I have perfected it.
Re the antifoul, I was told to use old fashioned grate blacking, which does seem to help as there is no fouling even after 6 month in the water.

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[ashanta]

Alan,


Whats an AH? Is it a Brunton Auto prop?

Regards.

Peter.

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[alan]

Sorry about that .......... I meant to say AP (for Auto Prop) ........ I'm so used to wingeing about my autohelm (AH), it must have been a Freudian slip !!!!!!!!

Apologies for confusion.

Alan.

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[Oldhand]

But Poole's silt sits on top of oil so its proabably an excellent lubricant!

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[Sinbad1]

Will

The Brunton is a wonderful prop but it needs a bit of tweaking to get it right. They will help you do this and its not a big deal.

First. Are you getting the forward performance you expected. If not then you need to have it repitched. They have to do this at the factory so it has to come off. You must indicate the increase or decrease in performance you require. The smallest pitch adjustment can make a huge difference.

Next....your 'cavitation'. This is most unlikely to be cavitation and will almost certainly be unbalanced blades. My understanding is that the blades are balanced within certain tolerances. I asked them to reduce these tolerances and rebalance and got back a prop that had suddenly lost most of it rumble and noise.

The guys at Bruntons are most happy to help. The new greased hub shows no sign of bearing wear.

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[Will_M]

I agree they are most helpful at Bruntons...

In fact they are manufacturing another set of blades and they them selves are coming to fit and try as the first set are definitely way out.

Results to follow.


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[qsiv]

Absolutely - our MaxProp works really well. The anode is important to look after (we are aluminium). Just occasionally it doesnt feather 100% - a brief snubbing of the proshaft always sorts it out.

The only issue that others have mentioned is lack of 'bite' when boatspeed is zero - but you quickly get used to it. As soon as there is even 1/2 a knot of boatspeed it behaves impeccably.

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[castaway]

Grate Blacking.. Im interested in this one as an alternative to the hard a/f I generally use... Where do you get it in the UK.. is it black lead??

Thanks Nick

<A target="_blank" HREF=http://www.yachtsite.co.uk/fairweather>http://www.yachtsite.co.uk/fairweather</A>

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[charles_reed]

There is less drag with an Autoprop than most folding props, they're equally good in reverse as forward which is totally unique for any prop - the only snag is there is a lag of a couple of revolutions whilst the blades re-pitch.

They are very affected by fouling and there is more noise and rumble than with a fixed prop.

What no-one seems to have mentioned is their unique ability to push you along, when motor-sailing, at just over tickover - that way you can really move around effectively in light airs.

I've had mine for 10 years, the bearings need annual adjustment and because of the additional weight the cutless bearings wear more quickly.

Compared to the fixed 2-blader speed under power went up by about 10% and over the original folding prop by 25% (and that was a Gori). The Folder wouldn't push you to windward in much over a F5, and the engine couldn't reach max power rpm under the same conditions with the fixed prop. Now with the Autoprop it just fines up the pitch and, whilst speed drops, the motor reaches optimum revs.

They're hell to clean whilst the boat is in the water, you need both hands and a bottle as well as a mask.

I certainly wouldn't want to change mine, even though the price of the nose anodes is utterly OTT. (I use a ring shaft anode which sacrifices before the boss anode)

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[Robin]

Charles

Did you find the anodes fell off halfway through the season? I asked Brunton about this (ours did) and they said put a dab of paint around the mounting bolt holes, stops them wasting away at that point. It seems to have worked so far this year.

Robin

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