Autoprop ?

[fstbttms]

Originally Posted by osirissail

If you examine the better prop shaft collar zincs you will see a hard metal "point" inside that "digs into" the prop shaft as the two parts of the zinc are assembled around the shaft.

The "Martyr" brand zincs that use a brass "beebee" as a contact point on the interior surface of the anode (the brand that West Marine sells) are Chinese-made crap, IMHO. I never install them on my customer's boats.

[Blinky]

I got a reasonably quick response to my e-mail to Brunton…………….
Thank you for your email describing the vibration with your installation.
Vibration can be attributed to many things on your boat and in our experience it is sometimes difficult to pinpoint the major contributing factor. Saildrives are generally very good vibration and noise free installations because the propeller, saildrive leg and engine are all fitted together as a single unit. It is obviously important that the propeller is correctly fitted with the spacer provided with the saildrive leg and that there is no movement on the shaft. The type of noise usually associated with saildrives is mostly a singing propeller noise, which is usually a high pitched sound. Other factors that can cause vibration can be attributed to the propeller striking or catching objects such as; rope, plastic, netting and other more objects solid,. Anything when in tangled with the propeller could induce vibration even after the offending item has been removed.
If the vibration persists then we are happy to carry out a free inspection but we will need to get the propeller back to our factory to investigate.
I did do a longish motor sail two weeks ago. The noise is no better but having put my engineer’s stethoscope on the engine, gearbox and saildrive there appears to be no bearing noise from the bearings. The noise appears to originate from the actual prop and is more of a cavitation noise which is amplified by the hull.
I intend to stand on the scrubbing pile, swap the prop for the original and see what happens. This should at least eliminate the prop as part of my eventual diagnosis.
I can then check the Brunton, make an anode adaptor plate and if necessary send the Prop back for checking.

[athene]

For anyone that's still interested in this subject, I've recently ordered a Brunton Autoprop for our Oyster 435 Athene of Lymington to replace a 25-year old Maxprop. Why? Because Maxprop quoted me over £4,000 for the new generation model (pitch adjustable underwater) and a 4-5 week delivery. Brunton quoted me a little over half that amount and a 7-10 day delivery. Once the Brunton is on, I'll be in a good position to compare the performance of the two. We had a Brunton on our previous boat, a Moody 346, and the lack of prop walk and self-pitching characteristics when motorsailing were a real advantage. Whether we get the same benefits on our Oyster remains to be seen. Athene has always kicked strongly to port in reverse with the Maxprop and, since we do a lot of stern-to mooring in the Med using our anchor, that's a real problem that I hope the Brunton will solve. I'll post a report once we've launched on the difference between the two props.

[fstbttms]

Originally Posted by athene

Because Maxprop quoted me over £4,000 for the new generation model (pitch adjustable underwater) and a 4-5 week delivery.

FYI- any Max Prop can have its pitch adjusted underwater. Is it easier with the Variable Pitch model? Yes. Is it necessary? No.

[Dockhead]

Originally Posted by athene

For anyone that's still interested in this subject, I've recently ordered a Brunton Autoprop for our Oyster 435 Athene of Lymington to replace a 25-year old Maxprop. Why? Because Maxprop quoted me over £4,000 for the new generation model (pitch adjustable underwater) and a 4-5 week delivery. Brunton quoted me a little over half that amount and a 7-10 day delivery. Once the Brunton is on, I'll be in a good position to compare the performance of the two. We had a Brunton on our previous boat, a Moody 346, and the lack of prop walk and self-pitching characteristics when motorsailing were a real advantage. Whether we get the same benefits on our Oyster remains to be seen. Athene has always kicked strongly to port in reverse with the Maxprop and, since we do a lot of stern-to mooring in the Med using our anchor, that's a real problem that I hope the Brunton will solve. I'll post a report once we've launched on the difference between the two props.

The Oyster 435 is a gorgeous boat.

I think we will all be very interested to hear about the direct comparison with the Max Prop. Please be sure to write it up in detail and post it here.

My Moody with a Brunton prop does not have much prop walk. A mild kick to port which disappears with 1 knot of way on. She has a bulb keel with partial skeg rudder. My previous boat, also with a Brunton prop, a heavy long fin keel boat with a large, skeg-hung rudder, had so much prop kick that "kick" is probably not even the right word -- she would spin off to starboard. She could not be reversed at all, really, which often made docking -- interesting, shall we say.

That tells me that the prop will not solve all prop kick problems -- I'll be very interested to hear how it works out on your Oyster, which has an underbody design somewhere between my new and old boats.

Cheers.

[athene]

Well - so far, so good with the fitting of our new Autoprop, which arrived just 10 days after ordering. We had to fit a 10mm spacer on our propshaft coupling, since the clearance between the tip of the blades and our P bracket when in reversing mode was a potential issue that we didn't have with the Maxprop. At the same time, Brunton recommend that the clearance between the P bracket and the boss of the propeller should not be more than the shaft diameter (which in our case was 38mm), so the 10mm spacer was a careful compromise. That said, fitting the new Autoprop took little over 10 minutes. First, you slide it on without the shaft key and mark where the back comes to on the shaft. That way, you can tell if it's binding anywhere when you next fit it with the shaft key in place. Fit and tighten the retaining nut with a socket spanner, lock the nut with a retaining screw that screws down on to the flat of the nut, attach the anode with the three nylon screws supplied and job done. We take to the water on Monday, so then the serious evaluation starts of how the Autoprop compares with our previous Maxprop.

[athene]

We’ve now had a month to evaluate the performance of our new Brunton Autprop compared with the previous Maxprop and, so far, the results are mostly favourable. We haven’t yet had the opportunity to test it in strong wind conditions with heavy seas or sailing at hull speed, but for what it’s worth here are the observations so far:

Motoring

At any given boat speed, engine speed shows a reduction of 400-500 RPM compared with the Maxprop. To put it another way, any given RPM seems to deliver an average increase in boat speed of between 0.5 and 0.75 knots. For example, at 1500 RPM our speed in flat water is 5.5 knots and at 2000 RPM around 6.5 knots; equivalents with our previous Maxprop were around 4.5 - 5.0 knots and 5.5 - 5.75 knots. Even at 1200 RPM - not much above idling speed - we still travel at around 4.5 knots. So the claims of greater efficiency and therefore likely fuel savings appear to be borne out.

Motorsailing

This is where the Autoprop really scores over the Maxprop. Motorsailing down to Levkas from Preveza in just over 10 knots of wind, we achieved 6.5 knots easily with sails hard in and engine throttled back to little over 1200 RPM. Getting the engine RPM just right for any given conditions does require a little trial and error at first, but once the boat is ‘in the groove’ it’s possible to pull the RPM right back without any sacrifice in speed. The Maxprop, by comparison, tended to cavitate once the sails started drawing and we could rarely get the combination of RPM and sail trim exactly right.

Slow speed manoeuvring

Berthing the boat - or, indeed, any kind of slow speed manoeuvring - does require a different approach to the Maxprop. There’s very little initial ‘bite’, since the Autoprop doesn’t assume its full pitch immediately, as the Maxprop does. This means that you need to apply much more initial throttle when starting off or changing direction and you need a certain amount of anticipation and patience until the Autoprop starts to bite. On the positive side, however, the considerable prop walk we experienced with the Maxprop is substantially reduced. As our boat (Oyster 435) has a semi-long keel, that’s a very welcome bonus.

Sailing

This is where we expected the Autoprop to suffer by comparison with the Maxprop, since (in theory, at least) a self-pitching prop should offer slightly greater drag when sailing than a feathering one. Surprisingly, that hasn’t been our experience at all. We reckon to go to windward at half the apparent windspeed (at least, up to 15-18 knots!) and downwind at a third of the true windspeed. We’re still achieving the same speeds under sail and I would say the difference, if there is one, is negligible.

Fuel economy

It’s still early days, but, as an indicator, our total engine hours since launch after fitting the new prop are 26.6, during which we used 72.66 litres of diesel. In other words, a fuel economy of 2.73 litres an hour. This compares with an average with the Maxprop of 3.3 litres an hour. All our motoring has been in flat water, so maybe this isn’t a fair test yet of the new Autoprop. Having said that, whenever you’re motoring in the Med it usually means there’s no wind and therefore the water is generally flat.

Maintenance

Of course, we’ve had no maintenance yet, but this is the one area where we don’t expect the Autoprop to measure up to the Maxprop. The latter is much simpler mechanically and only needed re- greasing once a year and dismantling, cleaning and re-greasing every other year (at least, that’s what I did). With the Autoprop, annual maintenance, like the Maxprop, is confined to cleaning off the fouling and re-greasing, BUT the bearings need replacement around every 1,000 hours (probably 5-6 years at our rate of engine usage) and that requires the initial purchase of a proprietary set of tools from Brunton at a cost of £120 plus a bearings kit costing £325. Leaving aside the initial tools cost, the replacement bearings cost amortises at around £60 a year (which doesn’t seem too high a price to pay for the benefits).

I hope this information is useful to anyone contemplating purchasing one or other of these two propellers and I would be happy to answer any questions forum members may have.

[Benronpro]

I have an Oyster 435 with a maxprop and it prop walks to starboard in reverse not port? ( it also prop walks a lot!)

[athene]

Originally Posted by Benronpro

I have an Oyster 435 with a maxprop and it prop walks to starboard in reverse not port? ( it also prop walks a lot!)

That's interesting. I don't know what engine you have, but ours is a Volvo Penta MD30A and the prop is/was right handed (therefore left handed in reverse). So, naturally, our stern kicked to port when reversing (see Propeller walk - Wikipedia, the free encyclopedia). I'd be surprised if your prop is left handed, but Oyster launched 65 of the 435s in all, so I suppose there were inevitable variations in the engine/prop combinations over the years.

GORDON KNIGHT

[Benronpro]

Ours has the MD31A engine. Haven't had her very long so I'm not overly familiar with the setup, I've just noticed recently some vibration in the shaft or prop so I'll be diving underneath soon as possible.

[athene]

Originally Posted by Benronpro

Ours has the MD31A engine. Haven't had her very long so I'm not overly familiar with the setup, I've just noticed recently some vibration in the shaft or prop so I'll be diving underneath soon as possible.

I'd be surprised if your prop isn't right-handed and, if you're experiencing a lot of vibration, there may be a problem with the set up or pitch of the prop that's causing prop walk 'the wrong way'. If the previous owner dismantled the Maxprop for servicing, it's quite possible it wasn't reassembled correctly and that might account for both the vibration and the 'incorrect' prop walk.

I think the only way you'll know for sure is to take the prop apart when you next lift the boat and check the orientation of the blades and the pitch settings. We found a pitch setting of 20 degrees worked best on our Oyster 435, but the original owner had the pitch set at 22 (or it might even have been 24?) degrees, which was much too high.

If you didn't inherit the instructions, the link below is a good guide to the process.

http://www.pyiinc.com/images/pdf/max-prop/PYI_Max-Prop_3_Blade_Instructions.pdf

GORDON KNIGHT

[Benronpro]

Originally Posted by athene

I'd be surprised if your prop isn't right-handed and, if you're experiencing a lot of vibration, there may be a problem with the set up or pitch of the prop that's causing prop walk 'the wrong way'. If the previous owner dismantled the Maxprop for servicing, it's quite possible it wasn't reassembled correctly and that might account for both the vibration and the 'incorrect' prop walk.

I think the only way you'll know for sure is to take the prop apart when you next lift the boat and check the orientation of the blades and the pitch settings. We found a pitch setting of 20 degrees worked best on our Oyster 435, but the original owner had the pitch set at 22 (or it might even have been 24?) degrees, which was much too high.

If you didn't inherit the instructions, the link below is a good guide to the process.

http://www.pyiinc.com/images/pdf/max-prop/PYI_Max-Prop_3_Blade_Instructions.pdf

GORDON KNIGHT

Thanks for all the great info. It will be interesting to follow the story of your Auto Prop upgrade. If long term testing proves beneficial I would be interested in the same conversion. As it is my Oyster has a large amount of prop walk to starboard in reverse and berthing her stern to in a narrow pen is adding to my collection of grey hairs...

[Blinky]

Hi all, took the boat out this weekend. Having put up with the cavitation and noise for 6 months. The fouling this year has been unbelievable in Portsmouth, it may be down to my new mooring or the fact we have not used the boat so much this year. Anyway, after cleaning all the barnacles and growth off the hull leg and prop, and wondering if the expensive anti-fouls are really worth spending out on? I was able to take a good look at the set-up. The first thing I noticed was that the Burnton prop anode was all but about to fall off, the Volvo ring anode was at least 2/3rds gone and the 6mm fixing screws were loose; despite lock sealing them in to place on fitting. My teardrop anode connected to the drive leg internally was fouled and in the same condition as it was 6 months ago. Placing the Brunton prop on the bench two 5mm hex head socket bolts from the Ambassador rope cutter dropped on to the bench!

The two bolts hold the rope cutter together and drive the cutter from two holes in the back of the prop. These are actually designed to shear in extreme conditions, which it appears is exactly what they have done. Not being driven the cutter blades would not have aligned with the prop blades which would have caused the cavitation and the noise.

Not being able to get a Brunton anode between tides I replaced the cutter bolts and after a good clean up, refitted it with a new ring anode. Refitting the original Volvo fixed blade prop.
Inside the boat I checked the resistance between the teardrop anode and the drive leg. The cables and crimps proved to be badly corroded and once replaced conductivity was restored!

Having brought the Brunton home and into my workshop I have given it a good clean and a meticulous examination there is no damage, bending, pitting or bearing wear.

So, what happened, and why did we not see the rope cutter fixings were sheared previously?

When I had the boat out previously I replaced the rope cutter PTFE bearings and secured the 5mm socket head bolts, using a lock seal liquid. This appears to have hardened under the heads of the bolts securing the head to the cutter face and clearance hole in the outer face plate. During our test runs after re-launching we must have picked up something nasty. The rope cutter cut it free but the drive bots seared allowing the cutter to turn out of alignment with the blades causing the cavitation. When we lifted the boat to check the problem I was preoccupied with the Brunton being the source of the problem. Without a very good look at the cutter it appeared to be intact and fully operational. When actually the 5mm bolts had sheared within the cutter as they are designed to do, but, they were held in place by excessive locking fluid under the bolt heads!
Back in the water now we have no cavitation or noise from the Volvo prop. The Brunton will be refitted this winter having been given a high polish and another grease change. But I have to say I will be looking in to making an adaptor plate to accommodate a better design of prop anode.

The Brunton has really made our boat more efficient, economical and better under sail. It has done exactly what it said on the tin! The only down side is the anode life, even when the securing bolts are covered with Sikaflex as suggested by Brunton.
All in all, I would recommend both the Brunton Auto prop 2 blade and the Ambassador rope cutter, both are a sound investment.

Hope my experiences have helped you.

Blinky.

[Pete7]

Originally Posted by Blinky

[COLOR=black][FONT=Verdana]Hi all, took the boat out this weekend. Having put up with the cavitation and noise for 6 months. The fouling this year has been unbelievable in Portsmouth, it may be down to my new mooring or the fact we have not used the boat so much this year. Anyway, after cleaning all the barnacles and growth off the hull leg and prop, and wondering if the expensive anti-fouls are really worth spending out on? I was able to take a good look at the set-up. T

What antifoul paint are you using? We are just north of Premier Marina and using Seajet 33 for the second year. Its expensive at £90 ($120) and very slippery when new but really needs regular use. Weather its worth the extra over Uno we used previously is debatable and I might go back to Uno if Luke in Fareham orders in another pallet load and sells it cheap.

Pete

[carstenb]

Hi all,

I have a 3 blade folding on my 40,3 jeanneau sun fast. Unbelievable prop walk and no reverse to speak of. Docking is, shall we say, interesting.

I want to mount a new prop and have looked at maxprop and autoprop. I understand the mechanical differences, one is a feathering prop the other a self aligning one.

I do need some advice as to which one to choose. I do need reverse, the prop walk i can learn to manage. But reading a lot of these posts, it seems the autoprop gives a lot of speed even at low rpm. I don't want the boat to go 4-5 knots at 1200 rpm.

Some of the posts i'm refering to at 6-8 years old. Technology has probably moved on.

Can anyone give me up to date information?

Thanks in advance