I bought a bass boat from Tenn. and we stopped in texas on the way back boat ran great. When we went fishing 2 weeks ago in New Mexico the boat had no power (7500 feet above sea level) so I checked with merc and they told me to change the jets in the carb from .074 to .068 jets. I took the cover screws out and looked in and could see the jets but I cant seem to get them to unscrew out of the carb. Is there any other screws to take out before the jets will come out? I didnt want to strip anything I was turning pretty hard and the jets wasnt turning at all. Is there a trick to get them out. Please let me know where leaving tonight to go fishing. Thanks