Mud and sand....now motor bogging down under load.

Any help or tips are greatly appreciated. I have a 2009 Mercury 60 HP 4 stroke. I was in the river this weekend and was trying to navigate some shallow water. Got too shallow and ran the prop through some mud and sand. Once I realized it I shut it off. Started back up and got into deeper water and as I gave it some throttle the overheat warning sounded and there was brief white smoke out of the engine. I shut it down again, gave it some time, then started back up and all seemed fine. She was still peeing water and all. I noticed the rest of the day that when I would increase power and put the engine under heavy load (before getting on plane) that it would bog down and almost want to die and then regain power. It only did this under a load. Whenever I was running at cruise rpm it ran like a top. Any suggestions or know what the culprit could be? From what I’ve read online I’m thinking I got some debris going through the impeller?

That's what it sounds like... it sucked mud up into the water cooling system and created a blockage of some type. That happened to me once (not nearly as severe) and when I disconnected the small hose under the cowling that led to the outlet water [censored] stream, it was all full of crud.I rinsied it out repeatedly and used a big paper clips to get stuff out of the small hose and it fixed it.

However, if it has a lot of sand or mud all in there, you'd probably have to take it apart to flush it all out. One thing I know, though: if the overheat alarm goes off, I'd turn it off instantly.

^^^This^^^

I might add, pull your thermostats as well to clean them out. Not uncommon for mud to clog them.

Bogging down ain't got nothing to do with your impeller I am afraid. You may want to take a look at the condition of your lower unit lube. I've seen your symptoms happen with a lower getting ready to go out.

That happened to my Merc 225 Pro XS a number of years age. Turned out I has sucked some sand and rocks up into my motor loading up on a very shallow ramp (lake was down 5 feet) blocked the thermostat on one side of the motor. The motor went into a protection mode and would only go to 2,500 RPM then slowly start to "die". Finally found the problem. Cleaned the sand and rocks out and it was as good as new.

Pull the thermostats they are clogged and engine going into safety mode for sure. I got stuck and had mine overheat and both thermos had muck all around them. You can run it with the thermos off the heads to thoroughly clean all the gunk out.