rough idle 305 carburator ?

[mxcobra]

I have the 898 merc sbc, You have always had to fether the throtle at idle ,Im getting kinda tired of it. I think its time for a new carb. and intake(intake is all rusty).
automotive intakes and carbs are so much cheaper. how much of a problem would it be to use them (auto) in the boat the manifold cant be that much dif? but what about the carb or should I just try and rebuild my current carb.?

 

[Bt Doctur]

Intakes I have but carbs MUST be marine use rated. You dont try to rebuild a carb.You either have the know how to do it or you send it to a shop.

 

[harleyman1975]

Agree with BT Doc. Your intake can be blasted and repainted and reused. Not much to go wrong there. The carb problem is most likely a plugged idle circuit, bad accelerator pump or idle jets out of adjustment.

 

[mxcobra]

Carburetor s are not that complicated, a rebuild should be fairly easy, the parts are only like 35 bucks

 

[NHGuy]

If you are competent with mechanical you can do it. There's a lot of detail to follow.
I'd get The Mercruiser manual and if it's a common carb also get the instructions for the carb from another source. Mercruiser lacked detail on my Rochester Quadrajet. But since it is so widely used there is plenty of help.
You might check beforehand for leaks around the throttle shaft,choke shaft and base plate. Get some carb cleaner and shoot it at those spots in bursts. Also check where the intake contacts the heads. If the engine picks up speed you found your issue,
If it's leaking around the throttle shaft entry you can rebush it, that's a real PITA. Probably ought to skip that and replace one that's that bad.