This will probably be a dumb question, but I am going to change fuel filters today and since this is my first EFI motor, I was wondering if it is necessary to pre-fill the new fuel filter or will the electric fuel pump handle it? In the past, I always pre-filled the filters on my carb motors with manual fuel pump. Does it makes a difference?

makes no difference, you might need to bleed some air out after installation.........What EFI engine are you talking about ?

If a merc MPI motor, fill the filter. The cool fuel pump can't pull the suction.

Yup, fill the fuel water seperator / filter.

If you have a inline filter too, that can't be filled.

said fuel filter, Ive not had any luck keeping the fuel in a horizontal filter, you guys are good.........

water separator filter is a no brain"r....FILL it

Exactly what it is. However, I changed the small inline filter today, but the main cool fuel filter would not budge. Somebody must have used an impact wrench to tighten it up (just kidding). It only has about 5 hrs on it, but I was going to change it out. I have never had a filter that tight before on any thing. It's tight in the compartment, but I will eventually prevail.

Thanks, I had decided to fill it regardless. It isn't that difficult. Just wish the other filter would have come off.

Merc 502 MPI

Mercruiser has a service bulletin out years ago to fill the spin on filter with fresh fuel then install properly.

Try giant channellocks to remove filter. Also you can carefully walk them loose with an air chisel on the base plate. If all else fails, drive a big screwdriver through it!

I've always filled the filter, but really don't like doing it. Guess with a gas injector they can handle a larger particle size then a diesel, would not dare do it with a diesel. The gas may be fresh but the container I would bet its not as clean as what comes thru the 10 micron filter.