Marine: Boating, Sailing, PWC, GPS and Navigation - MerCruiser 3.0 Rough Idle after New Carb put on

Doityourself.com community forum was created to provide answers to all questions related to home improvement and home repair. Doityourself community can help you find information about how-to topics on small fixes to large remodeling projects. With comprehensive how-to content and expertly moderated community forums DoItYourself.com makes it easy to tackle even the most complex home improvement projects.



PDA
marygee1
06-30-08, 12:30 PM
Long story...moter woul "Diesel" badly when shut off...my mechanic said that he read this was a needle valve in carb problem, we dicussed rebuild -vs- put on a new carb...we put on anew cardb. Came back and would start but shook the whole boat it was idling so rough...it would smooth out after about 5 minurtes of run time. THEN...we heard a hiss-hiss-hiss sound...mechanic said blown head gasket...replaced.

Now still idling very rough but will smooth out after 5-10 minutes then no problem...still deisel's on shut down but just barely. Is the rough idle a choke problem ? What should I look at for rough idling. I knoow I need a new mechanic but please offer suggestions

thezster
07-01-08, 07:11 AM
You're right - need a new mechanic!! Sounds as if your carb is running rich (dieseling and rough idle). As the engine warms up, the heat generated tends to, more or less, override a rich mixture problem. Could also be your choke is not opening up enough initially, assuming it's an electric choke - that opens the butterfly after a few minutes from starting. On the other hand, a new carb tends to run pretty well right out of the box, so to speak... making me wonder if you've got something else going on.