Rough idle, hard to start
 

2007 Mariah SX18, merc 3.0. Took the boat out yesterday. Started and ran fine leaving the ramp. Took a quick ride over to our anchor spot for lunch. After about an hour went to start up and the boat said no. Pumped the throttle a bit and it started and died. I basically had to do that then immediately throw it into gear and go. After that it started but idled roughy around 5 to 600 rpms. The carb was rebuilt about a month ago, but I'm wondering if the idle circuit is clogged a bit or just requires adjustment. Where should this motor idle? Ideals?

Re: Rough idle, hard to start
 

Sounds like a fuel issue for sure.
What grade fuel are you running in the 3.0L? How old is the fuel? The fuels of today deteriorate very quickly , especially in hot humid areas.
They seem to be susceptible to low octane fuels.
It should be idling in the 650 rpm range.
I'd bump to midgrade fuel , run a can of Seafoam or check out USA Fuels. There has been good results acheived with their products. I'd try that and see what she does before I'd start foolin' with the idle adjustment.:wink_thumbup: