CONTINUOUSWAVE

Would going to a stainless steel 14.25 x 19 propeller from an aluminum a 14.5 x 19 propeller [produce a] noticeable difference?

Or not?

I have an opportunity to get the stainless [propeller for] very cheap. Thanks for the help.

What is the horsepower of the engine?

How many blades does each propeller have?

Yes, or No. Depends.

Prop performance is not universal to size and material. Blade design is unique to each model of prop.
The size being close does not have any relationship to performance.

What is the model and year of the boat?
What is the year and model of engine?
What is the WOT range, gear ratio?
What is the mounting height of the engine (see FAQ)
What is the performance (WOT) for your current prop?

The material of the propeller accounts for a very small amount of the propeller's performance. The majority effect comes from the propeller's geometry; compare: pitch, diameter, number of blades, rake, and cupping.

Propeller material affects performance. See

Propeller Basics: Part 2: Propeller Materials
http://continuouswave.com/whaler/reference/prop2.html

Until the OP reveal the horsepower of the engine, it will impossible to form a cogent reply to his question.

If ALL other aspects of a propeller remained constant, an increase in propeller diameter would suggest an increase in propeller load on the engine turning the propeller shaft.

Please note: The originator of this thread has never returned to participate or acknowledge the discussion. This is an annoying behavior. If you want to initiate a discussion, please have be courteous and come back to read the comments.