[C320-list] Optimal Speed and Lower RPM concerns- Yanmar 3GM30F and Autoprop

[David Cushman]

I recently installed an Autoprop of the size recommended by King 
Propulsion. We just completed an 8 day trip with some days that had 
significant motoring and  I am extremely happy with the performance over 
the three blade fixed that came with the boat. My boat speed and the 
engine RPM closely match the data furnished by Dick Walker, previously 
posted on this discussion forum. I notice that my fuel consumption seems 
to be higher at each RPM setting than when using the Catalina standard 
factory wheel. This makes sense to me. It is still much better economy 
than before. What have users found to be the optimal cruising speed for 
fuel economy on longer trips? Are there any concerns running the Yanmar 
3GM30F at the lower RPMs since hull speed is met and the much higher RPM 
is no longer needed? I know that diesels are supposed to run under 
adequate load and I have read several blogs with slightly mixed 
messages. To me it seems that the feathering of the prop assures that 
the self pitching keeps the engine properly loaded at the lower RPM. 
Opinions and observations are welcome.

Dave Cushman

It Tips

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