496 HO problem
 

I have a 2002 Nordic Rage with a 496 HO in it and I am having a running problem with it. At 4500 RPM's it starts cutting out and has no acceleration until you come off of plane and start throttling back up. It pulls real strong with no problems until you get to 4500 Rpm's and the longer you run the boat it will start happening at lower RPM's. I have replaced the spark plugs, both batterys (has 1 bad one), and drained fuel filter and it was good for a couple of trips out and then started acting up again. I replaced both fuel filters this past weekend and it did not help. I was wondering if anyone else has ran into this problem and what solved or if anyone has any advise. This weekend I am going to check fuel pressure and alternator. I have not had it scanned yet, My boat place has a 5 week wait right now.

You really need to get it scanned could be a faulty injector, coil pack, plug wire or even something blocking your fuel flow from the tank like a pinched line or a plugged pickup tube.

Fuel supply issue for sure.

That is what I am leaning towards right now, hopefully not a bad pump.

I had a 2001 that had the same problem and is was a plugged screen on the side of the fuel pump.

Thats what I was thinking as well.

Had a guy here in Jax with them in a baja. Same problem and it was a clogged screen. Ethonal does wonderous things

Had same problems when I had 496's. Fuel pump, and I have a couple left over. Both high and low pressure.

How much are you wanting for them and what should fuel pressure be?Just in case I one.

Troubleshoot then replace!!
 

Slow down there Partner! You are starting to replace parts like a drunken sailor!
First for what boaters sometimes like your self do is spend $500 or so replacing needless parts instead of spending $400 on a Rinda scan tool and checking a lot of problems your self!

I WILL SAY THIS AGAIN VERY CLEARLY AND COMPLETELY! IF YOU OWN A BOAT WITH A MERC , VOLVO, MARINE POWER, CRUSADER, ETC. 496 ENGINE -BUY A SCAN TOOL AND KEEP IT IN THE BOAT!!!

Second- on the early Merc 496's years 2001 thru 2004, the Cool Fuel I systems with a spin off canister type fuel filter, their is a small inlet screen on the intake side of the primary fuel pump, the one under the spin -on filter. Remove the screen and check for clogging.

The only correct way to check fuel pressure on an EFI engine is under load in the boat! Go to a Napa or auto parts store, buy a fuel pressure gauge and screw it on the Schreader valve on the fuel rail under the rear of the coolant overflow bottle on the Merc and run the boat under loads up to 4800 rpms. The fuel pressure should be about 41-43psi at idle and about 39-43 psi at high rpms. IF IT IS LOW, AND YOU OPERATE THE ENGINE AT HIGH LOADS LIKE THIS IT CAN LEAN BURN THE ENGINE AND DO A LOT OF DAMAGE!!
If its low under load look at the fuel feed and pump system, but try not to just throw parts at the engine until you isolate the problem! You are just usually going to waste a lot of money and frustrate yourself!
Remember, boating is supposed to be fun!
GOOD TROUBLESHOOTING IS AN ACQUIRED SKILL, IT TAKES PRACTICE AND PROPER PROCEDURES!!

Hope these suggestions and advice help.

Best Regards,
Ray @ Raylar