Tunze 6105 question

[Mel 2038]

Hi, I recently acquired four Tunze 6105's. It clearly states 6105 on the motors. Two have a blue, fixed propeller, with no shaft coming out of the front of the propeller. The other two have a black, moveable propeller, with a shaft that sits in the motor, and protrudes through the front of the propeller, into the front housing. So, the question is, What's the difference? Older vs newer model? which one would be the newest version and why?

 

[rvitko Verified Sponsor]

The propellers were blue after mid 2010, at that point we started producing the propellers in house, older black is an RC model boat propeller we purchased. The fixed shafts started in late 2011, this reduced noise by about 10 db. The older one is from late 2008-mid 2010, the others are from at least late 2011.