First I wouldn't use that bracket. It doesn't have enough flotation to compensate for the weight of the motor.
Do NOT fill any bracket with foam. That would be putting a
band aid on a problem and by pouring 2 part foam in the bracket you will have a bigger mess.
In this pix is an example of changing motors to heavier motors. Notice the bottom paint and then the scum line. The thruhull is now under water at rest.
The cure for this is a larger tub/body to offset the extra weight.
