http://media.hobbypeople.net/manual/210985.pdf
Here is the manual for the .61 four stroke. The engines look the same side by side. the only difference externally is the size cast in the case and there's not much difference in the power. I don't know why they have the manual for the 61 instead of the 52? To my knowledge, they have discontinued the 61?
I like the APC 12-5 to use on the .52 instead of the 12-6. The APC 12-5 is a beautiful prop compared with the 12-6. However, I use the 12-6's on my Magnum 61's.
Enjoy,
Jim