What I have is a 2000 Velocity 320 with a 2006 496 HO and a 2008 496 HO. The issue is with the 06. He says it ran fine until he ran out of fuel, and now it won't run worth a crap. I did compression test on all cylinders, 145-135 across all 8. New plugs, #6 and #8 we're black and looked like oil covered. Starts and idle fine, 45lbs fuel pressure KOEO and running. Talked RPM if I stand the throttle but if I creep up slow, it starts to stumble bad and if you get past it, the RPMs surge with a steady throttle. Tried to water test it but it won't make more than 1500 rpm. Anyone ever run into this issue or have a direction to point towards? I have a techmate pro that he sent with the boat, but damn if I can find where it plus into. So I can't see any sensors or what's going on, it's trial and error for the moment.

So, you are fixing a 496HO engine for somebody else and don't know where to plug in the techmate???
Return boat to owner and have him take it to a qualified Merc tech

Your diag plug should be around where the oil filter is located.

The 2006 has the gen 3 cool fuel module. These are known for paint delamination in the lines etc that cause fuel injector issues. This is very very common. You need to take things apart and inspect for paint flakes in the system.

Another item that gets missed often times is there's a round disc fuel filter located inside the cool fuel module that people don't know about. They change the cylindrical element but don't know about the disc.

Good luck!

I was leaning towards all that until I saw consistent fuel pressure on the rails, but I'll definitely still pull the rails, injectors and the cool fuel stuff apart. Very much appreciated into.

For the diag port, by the oil filter was the first place I looked. Nothing there, only thing open is the larger 10 pin round connector at the back by the head.

On the 496s I've worked on (including my own 2004) the diag plug is tucked in right near the front of the port valve cover. Hopefully you can find it.

Danimal,

Send the injectors to Smitty (ArcticFriends). It's just cheap insurance. Even if it's not the injectors causing your problems, clean injectors won't hurt a thing.

Thanks. Brad.

I did find it after figuring out that I was given the wrong cable adapter. The smartcraft system takes a 4 pin connector and was at the back of the intake to starboard side. Can't find the diag port if you're looking for the wrong connector 🙄.