Motor is a 2002 496/mag. Boat runs normal until I push it above 4300rpms. After about 15 seconds it starts to bog down, rpm’s drop, than go back up, drop down, back up. It’s like the motor is starving for fuel. Pull back on the sticks to around 4000rpms and everything fine again. Open it up again and it starts again. Boat will run all day under 4000 with out a hint of a problem.

After changing the fuel filter and fuel water separator I made a few runs and the problem seamed to go away. But it was late and I was running out of daylight.

Do you think a dirty fuel filter will cause this or do you think I having bigger problems?

Have you tested since to see if it went away altogether yet? Reason I ask is I'm having what seems to be a fuel starvation issue but only with BOTH 496HO's? Changed the separators and pulled one inline to see if it appeared or acted plugged. I was able to simply blow thru it without any restrive resistance, but then again I'm not sure if that means anything with regards to fuel flow?

an '02 model boat...engine packaging most likely done '01. check the screen in the inlet of the high pressure pump. also I had a HP pump chit at 50 hrs on my '01 packaged HO's

My motors are late '04's with all the bulletins incorporated at that point, in an '05 boat with in-line filters added which I hear were put in place in 2002 for 496's due to some fuel tank crud issues getting to the motors/pumps. Not sure how the in-lines work in terms of micron filtering levels or how efficient they are with stopping large particles? Doesn't the separators come after the pump/s?

Actually tried a cheap fix by going to Pep-Boys and getting an automotive inline filter for a truck 496 ($7.99 ea. Purolator #F33144) but the ends where the line adapters screw into were not of exactly the same thread type, and weren''t as deep as the Merc models.

I had some engine popping/bog down type of problems as well that would begin occurring intermitenantly between 3000-3500rpm. I wasn't exactly sure of what it was at first---did a compression check, inspected cap/rotor, new plugs, new plug wires. Nothing worked until I changed my KE coalesant fuel filter water seperators...they were full of water. I have dual/seperate fuel tanks and perhaps one engine began having problems because it had more water....not exactly sure, but the engine still missed for about 30 more miles of boating that day---maybe because there was still some water trapped in the fuel lines between the filter and carb (????) and after that it dissappeared. So, it may take some running of the engine(s) before it completely clears out.