In Reverse engine kicks up - HELP

[Wsnapp]

Hello, first time here so please excuse my idiocy

Engine: 2000 Johnson 150

A few months ago I ran aground and popped my engine up. Ever since, whenever I go into reverse my engine creeps/kicks up.

I have been told it is the TNT main piston's breakaway or check value that is broken. BUT I can't find that part anywhere.

Anyone have any idea what is broken and what part I would need that would keep the engine down while reversing?

[boats.net]

Does sound like a valve is broken, unfortunately the only way to obtain the valves is to purchase the valve body assembly.

0435343 EVINRUDE/JOHNSON VALVE BODY AY $337.97