Boat has been running great all summer, On Monday the boat started idling rough and seems to lack power at the upper mid and top end I say this because normally I max at 4600 rpms and now I only spin at 4000 rpms plus its loses power intermitenly. I have an '89 350 Mercruiser 260 hp, I checked the carburetor seems to have fuel flowing in, Check the fuel filter and it was clean, no blockage. Checked the linkage and made sure it moves freely. I did not check the plugs to see if they have been fouled I know I should have. The motor runs smooth when you run it at a high idle. I'm going to check the plugs if they're fine, then it must be a bad fuel pump right ? I'm pretty sure its the original pump. Any input would be great?