I purchased a new boat with a 2003 Mercury 75HP and since the purchase the motor has fired up every time with no issues and runs fine. My only issue is that the idle seems a little rough and when I bump the throttle to engage just barely it sounds rough as well. The motor has a little shake to it as well when idling and when barely engaged. When I give it more throttle it runs perfect.This past weekend it wouldn't fire up on me without choking after I just ran for 30 minutes straight and then cut off one more time by the time I got in on the trailer. When I got home I hooked the boot up to run fresh water through it and it fired right up without choking and stay running the duration of the flush without dying. I'm by no means a boat mechanic but thought I would start out with new plugs. The previous owner advised it was just serviced in the winter however that doesn't mean much nor does it mean that the correct plugs were put in. Any other thoughts here on areas that I can look at before taking to my boat guy? There is an idle adjustment screw on the side however again not to too familiar with boat motors. Any insight is much appreciated.
