The good news is you never have to scrape sea growth out of your thruster again.
The bad news is you have to get wet.
Go on line and buy high density boat cushion foam that is 5" thick and a density above 2.5.
Measure the diameter of your thruster and then add 1".
Cut two pieces of the foam using a serrated knife to the thruster diameter and the added one inch.
(7" diameter thruster, cut foam with an 8" diameter)
Turn thruster battery switch off.
Put sign next to thruster control
"Do Not Operate"
Make a bucket of soapy water using blue colored Dawn Dish Soap. Add the amount of Dawn to water like you were going to wash dishes.
Put the round foam pieces into the soap solution and step on them to extract the air out of the foam.
Get in the water and shove the foam into both sides of your thruster.
Six weeks or six months later your thruster is clean as the day you installed the plugs.
Do not add too much soap it will attack your thruster shaft seals. The soap is to help remove all the air from the foam.
Do not put a chlorine pool table in between the foam plugs to sanitize the water. They will eat your seals and burn/melt the foam plugs.
You can cut a 1/4" thick starboard ring that is 1" diameter LESS than your thruster, cut a 4" center diameter hole (to accommodate the thruster center shaft) and tie a loop out of the front of the plug so that you can pull the plugs without getting wet using the looped line that is tied to the starboard ring on the back side of each foam plug.
I'm on the west coast of southern Florida with Warm water the sea growth will jam up your thruster in six weeks. I have used these plugs for six months now. My thruster blades do not even have slime on them. Clean as a whistle. Sea growth needs light and water movement. With foam plugs there is neither.
Now I have more time to party.