Mercrusier 5.7L efi throttle body fuel injection

[Billpat]

2001 mercrusier 5.7L engine, 200 hours, maintained well, freshwater flushed each use, I had a hard time starting the engine the other day. Finally started, spitting and struggling for a minute or two, then settle back to a normal idle.
When out on the water and when traveling over 3000rpm, I would hear an occasional violent bang or knock. Not consistent with anything except speed over 3000rpm. Could not reach normal speed of 42 mph (only 35) and could not get over 4000 rpm (normally 4500). Idles perfect and accerates fine. Just the banging every once in a while. (only under load) no change in speed and no influence from water conditions, I have changed plugs (perfectly normal) and fuel filters. Still having same Bang/Knock. I have a bravo III, checked for leaks end of last season and replaced lower unit old (normal) Any thoughts on this problem

 

[Reel Poor]

Re: Mercrusier 5.7L efi throttle body fuel injection

The first thing that needs to be done is that the Engine Control Unit needs to be checked for codes. If you don't have a code reader you either have to get one or have someone scan the system for you. There was someone here who posted how to make your own code reader with an L E D light (newportdave I believe). Maybe someone saved the diagram and could post it for you.

Check the fuel pressure. This requires a hi-pressure fuel guage. When checking the fuel pressure you have to check the pressure of the low pressure pump, hi-pressure, and also check the suction ability of the low pressure pump.

 

[calwldlif]

Re: Mercrusier 5.7L efi throttle body fuel injection

With out hearing what a bang or knock is
its hard to tell.
Wires?
Cap?
Check wires for cracks, abrations, resistance.
Cap for cracks, moisture, pitting.