496 Mag Ho misbehaving...help!
 

Off course it always happens on a vacation.

Ran like a top to start with. Then started to get a little hesitation when accelerating. Would clear up an run fine. Acting just like an old carb motor with the plugs loading up. Progressively got worse. This is over about 5 or 6 running hours. Now it is stuttering pretty bad accelerating...at about 4000RPM's it just starts cutting out and won't do any more(strated doing that 1st time I noticed at 4500 RPM's). When you come off plane and are idling for a minute or 2 it will backfire 2 or 3 times at about 10 second intervals(like 1 clyinder is firing late). The it will idle along with alot of surge. Once on plane it will clear up and run fine from 2500-4000RPM's.

I have checked the plug wires,changed the fuel filter, and looked for any connections that might be loose...but there are many. It is not sounding any alarms. The transom is as white as snow. Oil pressure,temp,and voltage are normal.

Obviously I have no scanning equipment available. Is there anything small or stupid that could be causing this? Would also love opinions as to what it might be. I believe the boat has probably not been run much for close to a year. I've put 8 hours on it. 2005 model. Now here's the really dumb one that I know the answer to bit need to appease my wife. How much risk am I taking to run the boat like this? It idles like a champ when first started.

Start with the basics and don't get wrapped too early on the complicated answers.

If no alarms, I would start with using a fuel pressure gauge on the fuel rail via the schrader valve and check to see what your fuel pressure is doing. Should stay strong up at 40-43 on the gauge. If it wants to drop off, then I would say boost pump has crapped out. Secondly if that checks, i would ensure you have your plug wires connected to the right spark plug. 496's are easy since each coil lines up with each plug. Outside fuel and ignition with no alarms, it's hard to say beyond that. You just have to take the troubleshooters process of elimination approach until you stumble across the culprit.