trouble with 7.4 mpi
 

today I was out on the boat by myself and wanted to do some testing with the k&n filter I just put on yesterday, the boat seemed to run fine hit the
throttle a few times and it felt fine yesterday I pulled a skier with no problems but when I got to some open water I went WOT it bogged I backed off it
seemed fine gave it throttle it bogged again then it got worse I couldnt get the motor over 2900 rpms(put on the stock arrestor no change) went back to
the dock (20 mins idleing up the river) checked a few things oil good, wires seem fine (it didnt sound like it was missing) checked one plug white no sign of
anything strange it may be a hair lean, prop seemed fine I couldnt feel and damge to it. this may or may not have anything to do with it but since I had
the boat once in awhile it would come off plane by itself and I would have to give it full throttle to get it back up to speed but in never bogged before, any
ideas I think I have a good guess but Ill wait to hear from you guys

Sounds like a problem with the fuel pressure. Also I would start by changing the fuel/water separation filter. If the plugs are WHITE, its lean, so don't run it hard till you find the problem.

:( I really hate to say this...but....
my engine did that a couple of times, then seemed to be normal, then it quit completely. If the timing slips a little, you would lose power this way. Mine never back fired or gave any trouble starting. ...the final problem turned out to be a distributor gear. It sheared of enough of the teeth to slip a tooth, an run for awhile before it shelled out completely. It only takes a minute to mark it and pull the distributor....you may want to check it first. GM/Mercruiser was known to have a bunch of "soft" gears out there. The replacements are hardened.
If that is it, flush the motor as good as possible per Merc. Change the oil & gear, then go.... Good Luck!!

I bought the boat last year in july so it is under warranty so the dealer is checking it out hopefully this week

bad fuel pump :)