Small Engines (Lawn Mowers, etc.): mower engine stops, blade guard, point hitch

Question
I have a powerpro 4hp 22" cut mower that I'm attaching to the end of an extension off of my three point hitch for cutting my river bank. The mower works fine for mowing grass. I removed the deck and now have just the engine with the blade exposed. I want to make sure my invention is going to work before making a blade guard for protection. I start the engine and it runs fine. When I lower the mower down into the light weeds the mower just dies after a few seconds. Does not having the deck installed have something to do with the engine stopping?  Thanks, Doug

Answer
What you are suggesting is dangerous at best.  I know that you will say now it's your invention and you would never sue.  But when you're in the hospital or disabled, your insurance company will try to.  Please rethink your idea or by a Wood's brand three point hitch mower.