Merc 525 help???
 

I have a 525 efi motor is poping under a load and has no power. i switched out the computers theres no difference fuel pressure is 40psi did anyone had this problem before please help thanks..

I don't know the spec but that fuel pressure seems low. I would expect around 55. Lean mixture can cause a backfire through the intake. But I would guess you have a burned or dropped valve. Possible due to the lean mixture if I'm right about the fuel pressure.

Do you have twins in the boat ?

yes i have twins in the boat they r both at 40 psi for fuel the other motor runs great. it has 180 hours on it.

40 sounds about right the specks are normaly 38 psi with vac hose on and 43 hose pulled off. still pull off you fuel filter and dump it in a glass jar or a clean coffee can and look for water or dirt. also check the ground cables to the batteries and engines make shur they are tight and clean. Was this your first run this year after sitting ? could be some left over old gas.

pull the valve covers

This started happing last year i change the fuel filters last year no diff and today i pulled the valve cover off to see if there is a bad spring but they all look good

If it's only doing it under a load, then start looking at the ignition system. Check the coils to be sure they are all getting power. Also, check all of the plug wires real good. Pull the plugs and make sure that none of the porcelain is cracked. Usually, ignition problems only show themselves under a load.
Eddie

Well then it sounds like it is time for a cyl leak down and compression test. May be a valve some place. But first have you done any tune ups lately ?

i agree with boat tec