I have a 1998 Mercury 150 hp XR6 that has been sitting in my garage for 4 months. I took it to the lake this past weekend and had the following trouble. First of all, the engine cranked with no problems, I ran it for about 15 minutes between 1/2 & 3/4 throttle. Everything seemed to be working great. While going to my second fishing hole I went full throtle and reached my normal speeed of 63 mph. Later in the day on the way back from fishing hole #2, I tried to go full throtle again but this time when I engaged the last 5% of the throtle my speed reduced and it sounded like the engine was bogged down. My top speed was then only 57 mph @ 95% throttle and only 54 mph @ 100% throtle. Could this be a problem with my rev limiter or some bad fuel? I'm at a loss. The engine has only been in the water four times since it's last service. Any suggestions on how I can better troubleshoot the problem? I don't want to have to pay for another service if it's something I can troubleshoot myself.<br /><br />Thanks for any help you can give.