1998 Volvo Penta 3.0

Boat was idling rough so I had the carburetor rebuilt. After that it wouldn't idle at all and ran rough at higher rpm's. Replaced plugs, wires, ignition coil, ignition module, cap and rotor. No luck, it still wouldn't idle and ran rough. Also, the spark plugs in cylinders 3 & 4 keep fouling out. Replaced the pick up coil and it fired up and seemed to run fine for about a minute, then it started running rough but it did idle. I shut it if off for a few minutes and then tried to start it again and it struggled to start, when it did finally start it ran really rough and would not idle, it would just stall out. The compression was tested, no problems there. Any Ideas? Thank you!

Are you familiar at all with how to dial in a carb and check/set timing? Have a timing light and vacuum gauge? Sounds like someone else did the carb rebuild and compression test. Did you replace the plugs, wires, coil, cap and rotor? Your firing order may not be right. Was the distributor disturbed at all during the process? Are you sure your wires on 3 and 4 aren't crossed or that you started one off on the cap?

Re: "Boat was idling rough so I had the carburetor rebuilt. After that it wouldn't idle at all and ran rough at higher rpm's."...
At this point I would have returned the carb to the rebuilder and not replaced anything that was in the engine when it ran ( but not idled well) before the carb "rebuild".