This last winter I had both of my 350 crusaders rebuilt along with Holley carbs 12R-10658B. When I had the boat back in the water, The engines would run fine the first time I would get up on plane. Then I would bring them down and up again and one engine would start bogging down around 3,800 rpm. Then the other engine would do it on a separate occasion. They have never done it both as the same time. They have two separate tanks but I have been switching the port tank to the starboard engine and vice versa. Now it doesn't matter which tank is on what engine, it happens to both. I have at the carbs rebuilt multiple times this summer and the first time the mechanic said there was some crap in the ports. Second time there was some and third time there wasn't any. After he would clean them and reinstall, they would run fine for a minute and then it would happen again. There is no water in the fuel, i have changed the fuel water separators three times. And doing a visual check in the tanks, there is no sign of debris. Any ideas?