Sudden rough idle and starting problem in 1973 mercuiser I/O

[muskrat808]

Hey there- 1973 140 hp merc I/O been running fine then outing before last idle became rough while bringing it in . Next time out started up fine first two times at dock then third start attempt took almost an hour of turning over and waiting . Finally got it to start by moving throttle out of idle position . Ran great at speed but rough at idle and died bringing in to dock at idle . Has fresh gas , new fuel tank ,lines, tune up and baffle on fuel tank vent inlet . Manual suggests a stuck closed automatic choke? Manual also shows a fuel filter for the Rochester carb at the fuel inlet but local Merc guy says no such thing . Any suggestions ? Thanks !

 

[muskrat808]

Re: Sudden rough idle and starting problem in 1973 mercuiser I/O

Thanks

 

[cr2k]

Re: Sudden rough idle and starting problem in 1973 mercuiser I/O

Your carb is probably in need of an overhaul. Also proper starting procedure is to pump the throttle one or two times, Push the throttle only button and give a little gas if cold starting.

Also check/replace the fuel filter for water.

 

[flintcam]

Re: Sudden rough idle and starting problem in 1973 mercuiser I/O

My 120 had the same problem with a rough idle after running it on the lake. My problem was finally solved by cleaning a rust filled fuel tank and fuel pump. Doesn't take much dirt to throw the idle off with a 2GC I have discovered. The choke shouldn't be too hard to eliminate as the cause.

Keep a can of carburetor cleaner handy for when your idle becomes rough simply turn off your engine, tighten up the adjustment screws and remember how many turns it took to seat them lightly, (don't over tighten), them remove the the screws from the carburetor and spray the cleaner with the attached plastic tube into the holes to unplug the idle chambers- replace the screws and springs in the same position they were in by seating them and turning them counter-clockwise the amount of turns that were previously determined. Once you get all of the dirty components out of the fuel system it shouldn't be such a problem.

Some Rochester 2GC carburetors do have a fuel filter but some don't- must be 50 models of 2GCs but it appears they all do need rebuilt, (cleaned out), quite often.