Tomek, you're in Penetanguishene ??? go figure. We're at BayMoorings.
As above the 29hp came as part of the Mariner package which most in this area seem to have. Where have you been looking.
We've done 4 seasons on Georgian Bay with ours. The 29 wil easily get 6.5 knots at cruising speed, not sure what you'd get on the 19. The 19 might be fine for getting out and back into the marina, but in our area we tend to motor quite often. I seldom will put the sails out until I get to Outer Penetang Harbour and often will motor up past the "Slot" on the west side of Beausoliel to avoid tacking back and forth dodging the powerboats.
We've taken 1 week, 1 1/2 weeks and 2 week trips up to the Bustards and Baie Fine. With wind and weather conditions we motored as much as we sailied. Can't imagine how much longer it would take with a smaller engine.
Also, make sure if you look pre mid 2005 that the heat exchanger has been replaced. The 3YM30 had an overheating problem ( I did on ours ) and Yanmar replaced with a bigger heat exchanger.
Maybe you could buy our 33 and we could get that new H39 we saw at the boat show.
Let me know if you have any more questions, more than happy to help.