2002 Mercury 150 xl swb Saltwater

I'm having a problem with my outboard, It idles fine and runs in low gear fine, but when I advance the throttle around 4000 RPM. It misses and runs rough. it eventually gets up to speed but it misses and has to take time getting there. I changed the in-line fuel filter, and changed the fuel/water seperator, even added some water remover to my fuel....still nothing. The spark plugs are fine, none fowled??????

Re: 2002 Mercury 150 xl swb Saltwater

There are many possibilities and guessing at the cause is often not reliable. Also, replacing parts until the problem goes away is often a more expensive and frustrating approach than doing some systematic troubleshooting. If you do some troubleshooting and report the results here, you will more likely get responses that will identify the particular cause of your problem and/or eliminate what is certainly not the cause.

I would suggest first checking for failed spark and if that checks out OK, I would next check for failed fuel delivery. Following are two troubleshooting guides I have found to be useful in the past. There are also some FAQ and posts on this forum that describe troubleshooting methods. Good luck....

Ignition: http://dolphinmarineservice.homestead.com/ign5.html

Fuel: http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Mercury-Mariner/2001/EN_17.PDF