Mercury 40 won't rev up

[tysonnathan]

I have a question on behalf of my friend. My buddy has a 16 ft Tracker with a late 90s, 40 horse Mercury 2 stroke. He took it to the river the other day while the water was a little too low. He kept running into shallow spots and pumping sand into the motor. I got to the river that evening and he said that his motor wasn't pissing. I took the rubber hose off that leads to the pisser fitting, slung the sand out of it and got it pissing again. He decided to go back down the river one more time to hit another fishing spot (said he could avoid the sand bars this time). Well, he didn't. Got it stopped up with sand again. He ran the boat back up river with the pisser barely dripping. On the way back the boat would barely rev up. It just runs at a fast idle with the throttle all the way up. I cleaned out the hose again, it started pissing again, but it still won't rev up. I don't think the motor overheated... The hi temp buzzer never went off and the motor was cool when he got back. Anybody got any ideas as to what might be goin on here?
Thanks,
tn