I am afraid I might have been badly ripped off on a 98 Nissan Ns15d2 motor that I just bought used. I just took the boat out to the lake yesterday and the engine starts up fine, first pull usually, idles OK, maybe a little rough, but when I try to go if I give it gas to fast or just trying to go full throttle it would bog down and die. The problem seemed to get worse through the day. Both Spark plugs looked good at the beginning of the day, by the end the bottom one was wet and pretty dark the top was brown and dry. I've done a compression test on it and it seems good to me 110 and 112. Gone through the fuel lines up to the full pump and they are all clear the filter is clean. Took the carb off and it was very clean inside so I think the previous owner had rebuilt it to try to fix the problem, fuel pump diaphragm looked good as well. Tried starting it up and disconnecting the plug wires one at a time and it wouldn't run with either plug disconnected. I also tried replacing the plugs, and that didn't help. I'm a little stumped about what the problem could be at this point. Does anyone have any ideas about what else I can check?