Mercruiser 140 Surging/Sputtering

[Ithinkican]

Hi, Here is what i have and whats been done..I have a 21ft cuddy, with an 88 mercruiser 140 i/o..I have rebuilt the motor,head,carb,and outdrive. I also have new fuel pump, filters, cap, rotor, points, wires, and sparkplugs. The boat has been running great, but just the other day when ever i try and bring it above 3,000 rpm it starts to surging and jumps rpm and back fire, but just the other day she ran great. It idles nice and rides good at 2500-3000 rpm but once i try and go above that its no good..just looking for some ideas on where to start? any help is very much appreciated. On a side note i did try different gas already thinking it was bad..
Thanks
Nick

 

[Alpheus]

Re: Mercruiser 140 Surging/Sputtering

Check fuel filters and fuel pressure. Make sure no loose connections on your coil or loose plug wires.