DIY Prop

Hi I'm Jason,
I design boats for the past 5 months in sketch up.
Now that schools and shops ate closed I decided to modify a Intex Challenger 200 that I have and afterwards donate it to my best friend!
I am thinking of powering it with an electric 250w motor.
Can someone suggest me a way to make a diy prop for it??
I would like it to be made out of household items.
What size should I make it?
From which materials??
is it a good idea to use a part from a PC dc fan?
Have in mind that the boat is mostly a toy and not a high-performance vehicle!!! Kepp t simple thank you

 

Better than DIY, just try a small plastic model airplane propeller, they come all sizes and are very low cost. Without knowing your boat details and design RPM you should try a few sizes.

 

You can try the PC cooling fan.
What is the RPM on the motor and the total weight of the boat including everything?

 

This is the real question. 250w is ~ 1/3 hp. If it makes that a high (1800) rpm, then you are going to be real inefficient and not able to turn a proper propeller. For a motor that big a 6-9 wheel is indicated if you can slow the motor to a proper speed.