welcome to IDA poker
One thing that I have heard from many new boat owners who underpowered there boat is ” I wish I would have maxed out the horsepower”
I don’t own one of these but I have to ask what is the primary use of the motor. Fishing or recreation? Fishing the 175 will get to your spots quicker, may be more of a gas hog, might not troll down as good if your a troller.
Recreation will pull the kids faster, may use more gas. Can get to a good spot quicker.
The 150 will not go as fast, will get better fuel economy, should troll down better.
Another question are both motors 4 stroke??
if you can get either one of these motors in a 4 stroke then I think you need to flip a coin to see which one to purchase.
Just my 2 cents worth!
I know you will enjoy the boat because its a Ranger!!