I have a 1987 21' Wellcraft 210 cuddy with Merc. 5.0L/Alpha One outdrive. Last year toward the end of the season when I would go to WOT the engine would cut out and then pick back up and run just fine. I figure there was some dirt in the carb. so I rebuilt it over the winter. I have taken it out about 3 times this season without a problem. The last time I went out it was running fine until we started heading back I was running at cruising speed when I noticed that the engine would lag and then pick up, lag then pick up. I got worse as I went until it just died. It started right back up but it was all I could do to keep the boat on plane without the engine bogging down. The engine lag would get worse with rougher water. I finally got it back to the dock. I thought maybe it wasn't getting a consistent fuel flow so I replaced the fuel pump. I also replaced the spark plugs because I had them and was meaning to replace them. When I started it back up it cuts out and back fires when I throw the throttle forward. I have not had it back out yet, but since it is not running right I don't want to chance it. It will start every time but will cut out, backfire, and die if you throw the throttle forward. Any ideas what the problem could be? Thanks...
