Autoprop ?

[j.g.evans]

Thank you Gord May. My Aotoprop is number AP4031 and therefore is in the range of propellers in the recall range, AP2902-AP5299. Long before I mounted the propeller I had e-mail correspondence with Brunton where I sought information and provided my serial numbers. There was no mention of a recall. I will use this recall information to see if Brunton will redress my missisng blade. I think I will have to call them as a menber suggeted because there has been no e-mail response.
Jim Evans

[jayncee]

Our boat was purchased new in 2003 and our Autoprop was serviced in May of 2007 (as it had been every year) when our boat was hauled and we lost our prop in early October. As I have stated before we really liked it but will not get one for our new boat. Right now we haven`t decided what to get if we change from the prop that came with our boat. We may consider a Campbell sailing prop that a friend of ours recommended--no blades to lose!!!

[vacendak]

an excellent opinion about AutoProps from the guy I trust:

I don't like the Autoprop. It is ugly and I don't believe their claims about being low drag under sail.
Those props have been known to generate enough drag to start the engines on fast catamarans

[dkall]

Prop shaft needs to be locked to for prop to fair. Who is this ... guy? I've read all I can about them for 7 years and never once came across any reference to starting an engine! Never once. But I'm not defending Autoprop, just reporting my experience and the prop will spin a loose shaft and the shaft needs to be locked.

[rgm.nz]

Glad someone mentioned the Campbell prop . Also have looked at that . Does anyone have one of these fixed blade props on their sailboat ? Would appreciate hearing what your experience is . Am I mistaken or did Practical Sailor test these a few years ago ?
RGM

[j.g.evans]

I had a bad experience with my 3B autoprop. One blade fell off. Autoprop-UK has not answered any of my e-mails other than to say they would get back to me. Over 1 year ago.
I didn't find it very smooth and I had bad luck with it catching weeds. I bought a feathering Autostream and think it is better.

[Silver Cloud]

Does anyone know what the Autoprop warranty policy is ?

[SydneyTim]

I finally fitted the old autoprop to our Passport 51 and now have the stats from 2 season of crusing one with fixed 3 blader, one with Autoprop.

With AP we do same speed at 60% of revs and therefore have averaged 4.2 litres per hour rather than 6.4 previously.

Boat handling the same as the fixed, possibly slightly quicker stoping but marginal.

I have always doubted the benefits of less drag from folding props especially on a boat that fully laden weighs nearly 24 tons. However to my total astonishment we have gained 0.75 - 1 knot of boat speed since fitting it, so we can now sail in 8-10 knots of wind when before we needed 12+ and in the trades we are doing 8.5 rather than 7.5 quite a difference!

This only compares an AP to a fixed prop, so no help in the debate of which is the better folding prop, but in summary I think it's great.

[sailvi767]

If you are doing the same speed at 60 percent of the revs it is quite likely you are going to cause serious long term damage to your engine. Its very important with almost all diesel engines that they are run in their recommended rev range. Its usually a narrow band something like 2800 to 3200 RPM. This is normally measured at full power.

[Elie]

I'M quite surprised of this kind of opinion regarding opp
erating ranges of diesel engines. Why does diesel engine marine applications be so special that it requires to be operated in such limited range of rpms or risk serious damages. Diesel car engines run in general à low rev, to save fuel and respect speed limits. If the prop is better conceived, and has enough power to push the boat at good clip at lower rev, it means simply that it is more efficient, witch is good in my opinion. Modern diesel engines for marine application are essentialy car engine equiped with heat exchangers, and a simplified antipollution system. I nerver saw anywhere such limitation for road applications, on the contrary. I think that many ideas on marine engines comes from an other era where diesel engines were huge finicky monsters that needed to be pampered. This is not the case anymore. I hope.

[SydneyTim]

Originally Posted by sailvi767

If you are doing the same speed at 60 percent of the revs it is quite likely you are going to cause serious long term damage to your engine. Its very important with almost all diesel engines that they are run in their recommended rev range. Its usually a narrow band something like 2800 to 3200 RPM. This is normally measured at full power.

My long term damaged engine has done 23,000 hours in the last 22 years, been round the world twice and still purrs along quite nicely thanks

It's also one of ht eold finicky monsters more commonly found in London Taxis and where they spend most of their life in traffic at low revs. It did the last circumnavigation over 8 years with the exact same prop and exact same engine revs under the old owner with no problems. Obviously it will now explode on me after that praise for it!

[dkall]

I think the thing about engine rpms has to do mostly with cooling. Some older engines seemed to be at the lower limit for water flow for cooling. My volvo barely put out much water. So if I was under a good load and turning the engine over 50% then I wouldn't be getting enough cooling. With other engines like the Perkins I have now there is so much water being pushed thru I believe it is a non issue.

Case in point. Years ago I worked on a Tayana V42. Somewhere down the line they factory had installed a transmission of 1:1. the prop put on was for a transmission of 2:1. They were getting hull speed at half throtle and an overheaded engine. As this was still under some warrenty issue with Southern Offshore Yachts a co-worker and I were asked to look at it. Someone earlier had disconnected the temp sensor and said all was ok. Luckily not much time had gone between that and when we were called. We discovered that the tranny was 1:1 and when the prop was resized for the correct rpms then the heating /speed issue went away.

[sailvi767]

I should have put in my post the engine should make the rated RPM at full throttle. It does not have to be run in that range. Yanmar as well as other engine manufacturers will void your warranty is the boat is not propped correctly. There are a several different reasons for this however Torque and HP verses load are the main reason. You don't want to lug a engine on a boat anymore then a car. Its not really a valid comparison car to boat however as few boats have 5 speed transmissions.

[hellosailor]

As I understand it, the "thing" about rpms on a diesel engine is that among other things, they coke up (build up carbon deposits) if thye are not run under sufficient load, they literally NEED the load to blow the deposits off and keep the cylinders clean.

This applies less to turbodiesels and some modern designs, and more to traditional "this old boat" classic diesel engines. It is the same reason that diesel owners are told not to run the engine for long periods at idle--you'll just build up carbon deposts internally and hasten the teardown time. The whole engine is designed to operate under a limited steady-state range of speed and load. Gasoline engines are very different, they are designed to operate under a much wider range and a more variable one.

[Elie]

The beauty of Autoprop idea, is that is ajust the pitch to the load and speed... To a point. So when the load is light, the pitch will increase and therefore a higher speed will be reached at lower rev. Inversely, when the going gets tougher the speed will decrease by decreasing the pitch, so for certain rev, the speed would be much reduced, at the same RPM. My engine is also a Perkins of recent vintage, and its cooling is as good and precise as a car's engine.