how well would a trolling motor power the oday 19. just for getting away from dock and back to it?
was looking at 45 pounds of thrust
I have used a Minn Kota Endura 50 on my O'Day 19 with great success. Top speed is limited to 3 knots due to the propeller pitch. But it is quite adequate for maneuvering around docks and mooring fields.
If the wind gets too strong, the wind may push the bow around faster than the motor can push the stern to compensate.
Beyond that, remember that the Group 24 size battery will not last for more than an hour at full speed.
Make sure the battery is a true deep cycle battery - NOT a dual purpose one.
A pair of golf cart (GC2) batteries will give you 230 amp-hours verses the 70 amp-hours of the Group 24.
But you choice depends on how much you will really use the motor. If you are focused on sailing, the smaller battery may be sufficient.