how bad (if any) is it to have your motor suck in muddy/dirty water when the skeg starts skimming the lake floor?

as long as you can get it to clean water and it flushes out, it should be ok. But, If the dirt does not flush out and it drys in the motor you could be in for some problems.

This just happen to my brother last month. He has a 125 Hp merc and ran into some mud. being that he is new to owning a boat, he never got the boat in clean water to flush it out. Next time he took the boat out. He noticed that no water was coming from that jet on the side of the motor. he didn't run it, just put it back on the trailer. Good thing. the mud had been thick and when it dried it made the impeller not work able, could have overheated and burned the motor up.

I know if I suck mud up in my Suzuki, I get to clean water and watch it to make sure clean water is coming out of it. But if you fish shallow you can't miss the mud. just make sure you flush the motor.