Re: Fixed Prop installation.

Bill Kinney

On Fri, Jan 14, 2022 at 12:56 AM, Rudolf Waldispuehl wrote:

Does anyone experienced the performance of the Original Fixed Prop delivered by AMEL, compared to the Pruntons Autoprop?


@ Mohammad, et all

I have seen you installed the fix prop last year. How was the installation? Exactly as Bill believed?

How do you removed afterwards without puller? Was it easy to take it off?



The Performance differences between an Autoprop and a fixed prop are complicated.  While motoring at cruising speed and on up to full throttle, the differences will be trivial, becasue this is the power range the fixed prop is optimized for.  At lower boat speeds, the Autoprop will be somewhat more fuel efficient by allowing the engine to fully power up at lower RPM.  In other words you will reach the same boat speed at lower RPM. This might matter to people who motor sail a lot.

The Autoprop is "fussier." It will show significantly reduced performance when fouled compared to the same level of fouling on a fixed prop.  (Although ANY fouled prop is a real fuel suck!)

Any feathering type prop will be MUCH better than a fixed prop at low sailing speeds. This will matter to some people more than others.  If you are the kind of person who starts an engine whenever boat speed drops below 4 knots the fixed prop has no real penalty here, but if you refer to sail along at 2 knots instead of listening to the engine, the lower drag of Autoprop (or any other feathering prop) matters--a lot.  

I find the behavior of the Autoprop in close quarters maneuvering to be less predictable that a fixed prop or a MaxProp, with more of a lag between throttling up and getting the boat moving, and less of a linear relationship between throttle and thrust.  But, to be fair, this might just be a result of me having far fewer hours on an Autoprop equipped boat.

You can not expect to remove a fixed prop without a proper puller. If it is so loose it just comes off by hand, it was definitely not as tight as it should have been.

Bill Kinney
SM160, Harmonie
Hollywood, FL

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