Autoprop propellors – updated views ?

I have been reading about the Autoprop propeller brand on this site and elsewhere. My Hull # 154 has Westerbeke 33 with Hurth 150 transmission. Currently have 18″ fixed prop which seems adequate under limited conditions; however reversing is tricky to say the least. Anyone else have experience with these props? I read Jeremy’s and David’s accounts, but these were quite a time back. Perhaps they and others might update their views. Autoprop has proposed a 19.5 inch (h5-506mm) for this application. Best regards”, Tim Baggett (#154, Sunshine)

a. Although I don’t have an Autoprop I do have a 3-blade Variprofile propellor. It is 21″ with approx. 13″ pitch and drives our boat quite well. It has a feathering propellor so that in reverse it reverses the blades and gives the boat equal thrust in reverse as in forward. This has greatly improved our boat handling in tight places and reversing is also improved somewhat. I don’t think you will ever get a Corbin to reverse all that well due to the fairly long keel. It will never back into a dock like a Beneteau with a fin keel. I think a reversing prop is the best you can achieve and the rest ….. well you just learn to live with it. Jack Verheyden (#127, Kathrian).

b. My Autoprop is working fine after 6 years. Jeremy Parrett (#101, Two Pelicans).

c. Responding to an email from Lester re: your Autoprop. Don’t know anyone that has one. I assume that Autoprop has the same profile Forward / Reverse e.g. my 20″ J Prop does. The only issue being the pitch. I don’t know if the Autoprop’s pitch is field adjustable. Again my J Prop pitch is and it took a few tries to get it right. Cheers, Frank Bryant ( #186, Visitant).

d. I only understand the prop diameter from your message and don’t see the pitch. This sounds too large for a 33 HP engine. I have a 40 HP Pathfinder and my prop is smaller than the one you refer to, at 18″ dia and 12″ pitch. It is also an H5 with 3 blades. Regards, David Salter (#050, Opportunity).

e. This response might be a bit late to be of much use to you but here is my experience with Autoprop… Our hull #155, “Blue Run” has a Westerbeke W58 with a Hurth V-drive transmission (15 degree down angle). Engine under the companionway steps. I installed an 18″ Autoprop in 2006. Under flat water no wind conditions we get 6.5 knots at about 1800 rpm. At 2100 rpm (the engines torque peak) we will make 7+. With wind we lose about a knot and with waves in the 3 to 4 foot range about 2 knots all at the same rpm. I do not usually run at higher rpm however the engine is rated for continuous output at 3000 rpm and a maximum output at 3600 rpm so there is some reserve available. I have been very pleased with the performance of the propeller. Regarding backing: the Autoprop has lots of bite in reverse however the geometry of the hull, the 15 degree downward slope of the propeller shaft, and the shaft offset to starboard combine to create a substantial prop wash effect due mainly to the wash from the propeller hitting the hull and pushing the boat sideways. This effect will vary from boat-to-boat depending on the geometry of the drive-train. With a sail drive the prop wash effect should be near nil and only the prop walk will be present. A boat with a flat or near flat bottom will be little affected by the prop wash.
Something unrelated to the propeller that can affect backing is the installation of a hydraulic autopilot servo. If it limits rudder angle on the wrong side it may make it impossible to compensate for the prop walk/prop wash effects. George Weeks (#155, Blue Run).