Starts but idles rough
 

I have a Mercruiser 3 Alpha in my 1996 Shabah 180.

The engine will start fine (now I charged the battery), but when it starts it idles kind of rough, keeps drifting around the 5K RPM mark, drops RPM till it almost stalls and then raises RPM back to just over 5K.

I bought it a few months back and haven't yet had chance to take it out in the water, so I'm running it on the driveway with the trim down and water cups.

Anyone know what may cause the rough idle?

I think the boat has been sat unused for some time before I bouagh it, so I'm not sure if that's related.

Oil & Temp look good.

I'd appreciate any pointers.

Chris

Re: Starts but idles rough
 

Clean (or new) plugs? fresh gas?

Re: Starts but idles rough
 

Did you test drive it before you bought it? If so, did it run ok then? If not, I would go with mikeyt and pull all the fuel out and replace. Also, if the prior owner had it sitting awhile(not winterized), maybe plugs are shot and carb needs to be rebuilt.(assuming its not fuel injected)